WO2019030939A1 - Screen printing metal foil mesh member, screen printing plate, and method for manufacturing solar cell using said screen printing plate - Google Patents

Abstract

This screen printing metal foil mesh member is a screen printing metal foil mesh member which, when used, is integrated with a resin forming a printing pattern, and which is made of metal foil. When a plurality of opening parts arrayed at a pitch X in one direction of the metal foil mesh member have an opening width Y, and a rib which is sandwiched between two opening parts arranged side by side in the one direction and which is made of metal foil has a cross-sectional area A in a section taken in a thickness direction in the one direction, the opening width Y is 10 μm or more and 39 μm or less, a width C in the one direction of the rib is 30 μm or less, and a cross-sectional area B of the rib per unit length obtained by dividing the cross-sectional area A of the rib by the pitch X satisfies the relational expression 3 (μm2/μm) ≤ B (μm2/μm).

Description

Metal foil mesh member for screen printing, screen printing plate, and method of manufacturing solar cell using the screen printing plate

The present invention relates to a metal foil mesh member for screen printing, a screen printing plate, and a method of manufacturing a solar cell using the screen printing plate.

In many cases, crystalline silicon solar cells form a silver electrode by printing and baking silver paste in an arbitrary pattern on a silicon wafer by screen printing.

Generally, a pattern of a silver electrode formed on a silicon wafer is composed of finger electrodes and bus bar electrodes orthogonal to the finger electrodes. The finger electrodes have a pattern of 45 μm to 100 μm in width and 150 mm to 160 mm in length. The bus bar electrode is a pattern having a width of 1 mm to 2 mm and a length of 150 mm to 160 mm in the direction perpendicular to the finger electrode. These silver electrodes are necessary to collect electron-hole pairs generated in the silicon wafer by sunlight. On the other hand, the silver electrode on the surface of the silicon wafer is also a factor that blocks the amount of power generation by shielding sunlight incident on the silicon wafer.

In order to collect more electron-hole pairs generated by sunlight, it is necessary to increase the number of fingers on the solar cell surface. However, when the number of fingers is increased, the light blocking area on the surface of the solar cell, that is, the area of the silver electrode that impedes the absorption of sunlight increases, which in turn causes a decrease in the power generation efficiency. Therefore, thinning of finger electrodes is required simultaneously with the increase in the number of fingers. Specifically, fine line printing with a printing line width of 40 μm or less is required. In addition, when the wiring resistance of the finger electrode is high, the conversion efficiency is lowered, so that not only the finger electrode is thin, but a thickness of about 15 μm is required on average.

Some solar cell manufacturers print the finger electrodes twice in order to obtain the required electrode thickness, and the number of processes increases. Therefore, there is a need for a screen printing plate which can be thin and thick.

The manufacturing method of the screen printing plate using the metal wire mesh generally used for printing of a silver electrode is demonstrated. After a mesh woven fabric of polyester fine wires is stretched in an aluminum formwork, a mesh woven fabric of fine metal wires is adhered to a polyester mesh, and a polyester mesh portion overlapping with the metal mesh woven fabric is cut off. Thereafter, a photosensitive emulsion is applied to the metal mesh fabric portion, and a target printing pattern is exposed and developed on the metal mesh fabric to prepare a screen printing plate.

The metal wire mesh is pulled by the aluminum form through the polyester mesh, and when the strength of the metal wire mesh against tension is insufficient, the metal thin wire is broken and the screen printing plate is broken.

Patent No. 4886905

In order to realize thinning of finger electrodes on the surface of the solar cell, the wire used for metal wire mesh is becoming thinner year by year, and the number of fine metal wires is simultaneously increased to withstand tension even if the wire becomes thinner. It is done. However, even if the number of metal thin wire knitting increases, the strength of the wire itself decreases as it becomes thinner, so the wire breaks when foreign matter gets in between the printing plate and the object to be printed during printing. The risk of being If the printing plate breaks during printing, the silver paste on the screen printing plate will splash around, which requires stopping production and cleaning, leading to a decrease in production capacity. Therefore, there is a need for a screen printing plate that simultaneously realizes printing of thin and thick electrodes for improving the conversion efficiency of solar cells and strength that is resistant to breakage to prevent a decrease in production capacity.

It is an object of the present invention to provide a metal foil mesh member for screen printing having sufficient strength such that thin line printing with a printing line width of 40 μm or less is possible when used for a screen printing plate and the screen printing plate is resistant to breakage. It is providing a screen printing plate using foil mesh.

The metal foil mesh member for screen printing according to the present invention is a metal foil mesh member for screen printing made of metal foil which is used by being integrated with a resin forming a printing pattern,
The opening width along the one direction of the plurality of openings arranged at the pitch X along the one direction of the metal foil mesh member for screen printing is Y, which is sandwiched by the two openings aligned along the one direction When the cross-sectional area of the rib when cut in the thickness direction along the one direction of the rib made of the metal foil is A,
The opening width Y is 10 μm to 39 μm, and
The width C of the rib along the one direction is 30 μm or less,
The cross-sectional area B of the rib per unit length along the one direction obtained by dividing the cross-sectional area A of the rib by the pitch X is 3 (μm ² / μm) ≦ B (μm ² / μm) The relationship expression of) is satisfied.

According to the metal foil mesh member for screen printing according to the present invention, the screen printing plate using this enables thin line printing with a printing line width of 40 μm or less, and the screen printing plate is sufficiently resistant to breakage during plate making and printing. It is possible to provide a metal foil mesh member for screen printing having high strength and a screen printing plate using the same.

FIG. 1 is a plan view showing an outline of a metal foil mesh member for screen printing according to a first embodiment. 5 is an enlarged plan view showing a line pattern portion of the metal foil mesh member for screen printing according to Embodiment 1. FIG. FIG. 3 is an enlarged cross-sectional view showing a cross-sectional structure as viewed from the α-α direction of FIG. 2; FIG. 1 is a plan view showing an outline of a screen printing plate according to a first embodiment. It is the enlarged plan view seen from the squeegee surface side of the line pattern part of the screen printing plate using the metal foil mesh member of FIG. It is the enlarged plan view seen from the printing surface side of the line pattern part of the screen printing plate using the metal foil mesh member of FIG. FIG. 6 is an enlarged cross-sectional view showing a cross-sectional structure of the screen printing plate of FIG. 5 as viewed from the β-β direction. FIG. 6 is an enlarged cross-sectional view showing a cross-sectional structure of the screen printing plate of FIG. 5 as viewed from the γ-γ direction. FIG. 6 is a schematic view showing a relationship between an average area of printing pattern opening portions of line pattern portions in the screen printing plate according to Embodiment 1 and a printing line width of a line pattern obtained by screen printing. It is the schematic which shows the relationship with the printing line | wire width of the line pattern obtained by the metal foil mesh member of different thickness. When a rib width is too long, it is a schematic diagram which shows the mechanism in which a conductive paste does not reach to the following printing pattern opening part under a rib, and a disconnection generate | occur | produces in a printing pattern. It is a top view of a metal foil mesh member which has an oval-shaped opening. It is a top view of a metal foil mesh member which has a rectangular-shaped opening. FIG. 6 is a cross-sectional SEM image from the δ-δ direction of FIG. 5 showing the state of the periphery of the printing pattern opening of the screen printing plate in which the resin is laminated a plurality of times in the opening of the metal foil mesh member. It is the schematic which shows the relationship between the total thickness of FIG. 14, and the amount of dents of resin in the printing surface side in the periphery of a printing pattern opening part. FIG. 1 is a plan view showing an outline of a crystalline silicon solar cell according to a first embodiment. It is the schematic which shows the outline | summary of the manufacturing method of the photovoltaic cell by screen printing. It is an optical microscope image of the squeegee surface side which shows the line pattern part of the metal foil mesh member for screen printing. It is a cross-sectional SEM image which shows the cross-section of the rib of the metal foil mesh member for screen printings. It is an optical microscope image which shows the structure of the printed line pattern. It is an enlarged plan view which shows the line pattern part of the screen printing plate using a wire mesh.

The metal foil mesh member for screen printing according to the first aspect is a metal foil mesh member for screen printing made of metal foil which is used by being integrated with a resin forming a printing pattern,
The opening width along the one direction of the plurality of openings arranged at the pitch X along the one direction of the metal foil mesh member for screen printing is Y, which is sandwiched by the two openings aligned along the one direction When the cross-sectional area of the rib when cut in the thickness direction along the one direction of the rib made of the metal foil is A,
The opening width Y is 10 μm to 39 μm, and
The width C of the rib along the one direction is 30 μm or less,
The cross-sectional area B of the rib per unit length along the one direction obtained by dividing the cross-sectional area A of the rib by the pitch X is 3 (μm ² / μm) ≦ B (μm ² / μm) The relationship expression of) is satisfied.

In the metal foil mesh member for screen printing according to the second aspect, in the first aspect, the pitch X is 65 μm or less,
The thickness Z of the metal foil may be 5 μm to 20 μm.

In the metal foil mesh member for screen printing according to the third aspect, in the first or second aspect, the metal foil may be electroformed.

A screen printing plate according to a fourth aspect includes the metal foil mesh member for screen printing in any one of the first to third aspects.

The screen printing plate according to a fifth aspect is the resin according to the fourth aspect, wherein the resin covers the plurality of openings arranged along the one direction of the metal foil mesh member for screen printing;
And a print pattern including a plurality of print pattern openings in which the longitudinal direction is the one direction and the resin covering the opening is opened with a print pattern opening width W intersecting the one direction. It is also good.

In the screen printing plate according to the sixth aspect, in the fifth aspect, the average area of the plurality of printing pattern openings may be 1375 μm ² or less.

In the screen printing plate according to the seventh aspect, in the fifth or sixth aspect, when the thickness of the resin is E and the thickness of the metal foil mesh member for screen printing is Z, E ≧ 0.6 × Z and the relationship of (Z + E) /W≦1.33 are satisfied,
The total thickness (Z + E) is 10 μm or more and 45 μm or less,
The print pattern opening width W may be 10 μm or more and 39 μm or less.

The screen printing plate which concerns on a 8th aspect may be an electrode wiring application for solar cells in any of the said 4th to 7th aspect.

A method of manufacturing a solar cell according to a ninth aspect includes the step of preparing the screen printing plate according to any one of the fourth to eighth aspects and a solar cell substrate which is a printing object,
Performing screen printing using the screen printing plate to form finger electrodes on the solar cell substrate;
including.

<About the process leading to the present invention>
In the case of a screen printing plate using a metal foil mesh member for screen printing in which a large number of openings are provided in a metal foil, the present inventors screen printing using a conventional wire mesh member having the same printing pattern opening width W The inventors found a problem that the printed line width of the obtained printed pattern is thicker than that of the plate.

On the other hand, in the screen printing plate using the conventional wire mesh member, the present inventors found that the average opening area of the print pattern opening 52 formed of the wire mesh member and the resin shown in FIG. It has been found that it is smaller than the average opening area of the print pattern opening 17 formed of the metal foil and the resin in the screen printing plate 20 using the metal foil mesh member 10 in which a large number of openings are provided in the foil.

The average opening area per one opening included in the line pattern 1.6 mm long of a screen printing plate having a printing pattern opening width of 35 μm using a wire mesh member # 360-φ16 CL is 1032 μm ² . On the other hand, in a screen printing plate using a metal foil mesh member for screen printing in which a large number of openings are provided in a metal foil used for comparison, the average opening area is 1540 μm ² from the screen printing plate using a wire mesh member The average opening area is 1.49 times larger.
From the above, the area per printing pattern opening 17 of the screen printing plate using the metal foil mesh member is larger than the printing pattern opening of the screen printing plate using the wire mesh member, and more paste is discharged I thought that. As a result, it seems that the printing width of the screen printing plate using the metal foil mesh member for screen printing provided with a large number of openings in the metal foil is larger than that of the conventional wire mesh member.

Therefore, the present inventors investigated and analyzed the printed line width when the area of the print pattern opening provided in the screen printing plate using the metal foil mesh member was changed. Thereby, it discovered that printing line width became thin, so that the opening area of printing pattern opening 17 of the screen printing plate using a metal foil mesh member was small. Explain the contents of the survey and analysis.

The thickness of the metal foil mesh was 20 μm, the thickness of the resin was 10 μm to 13 μm, the tension of the screen printing plate was 24 N / cm, the printing speed was 200 mm / sec, and the printing paste was PV19B made by Dupont. Table 1 and FIG. 9 show specifications of other printing plates and printing line widths.

From the printing result shown in FIG. 9, the smaller the opening area is, the smaller the printing line width tends to be. The printing line width of 40 μm is estimated to be obtained by setting the opening area of the printing pattern opening 17 to 1375 μm ² or less. It was done. Since the opening area is formed by the opening width Y along one direction provided in the metal foil mesh member and the printing pattern opening width W formed by the resin, the metal foil mesh member for printing a thinner line pattern It is effective to form a small opening in the Examples of a method for producing a metal foil in which small openings are formed include a method of forming an opening on a metal foil by chemical etching, laser, mechanical processing, and an electroforming method. Chemical etching and electroforming are superior in that small holes are precisely formed.

Further, as shown in FIG. 10, it was discovered from a printing test comparing the thickness of the metal foil mesh member with 20 μm and 25 μm that thinner 20 μm foil is more suitable for fine line printing. The metal foil mesh member used for the printing test is obtained by etching the SUS301 foil. The opening width Y of the metal foil mesh is 40 μm, the pitch X is 60 μm, the printing pattern opening width W is 35 μm and 40 μm, the resin thickness is 10 μm, the printing speed is 200 mm / sec, and the printing paste is PV19B made by Dupont. is there.

From the experiments shown in FIGS. 9 and 10, in order to realize thin line printing, the inventors reduced the opening width Y provided in the metal foil mesh member to reduce the opening area of the printing pattern opening 17 of the screen printing plate It has come to be considered effective to reduce the thickness Z of the metal mesh member.
However, the strength required for thin line printing and screen printing metal foil mesh members can not be realized simply by reducing the opening width Y provided in the metal foil mesh member for screen printing provided with a large number of openings in the metal foil. . As shown in FIG. 11, even if the opening width Y is reduced, the width of the metal foil portion (referred to as rib 11) between two openings (hereinafter referred to as rib width C) is too long, 30 μm or more. Also, the paste 43 discharged from the opening can not reach under the rib 11 to the next opening. As a result, disconnection occurs in the printed pattern, and the height difference of the printed wiring increases, and the wiring resistance increases. On the other hand, if the rib width C is too short, the strength necessary for the metal foil mesh member for screen printing can not be secured, which may cause breakage of the metal foil mesh member.

Based on these findings, by improving the metal foil mesh member for screen printing provided with a large number of openings in the metal foil, a mesh member for screen printing that simultaneously realizes fine line printing and strength, and the mesh for screen printing The screen printing plate using the member can be obtained, resulting in the present invention.

Hereinafter, a metal foil mesh member for screen printing and a screen printing plate according to the embodiment will be described with reference to the attached drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

Embodiment 1
<Metal foil mesh member for screen printing>
FIG. 1 is a plan view showing an outline of a metal foil mesh member 10 for screen printing according to the first embodiment. FIG. 2 is an enlarged plan view showing a line pattern portion of the metal foil mesh member for screen printing 10 according to the first embodiment. FIG. 3 is an enlarged cross-sectional view showing a cross-sectional structure as viewed from the α-α direction of FIG. Note that the opening 12 in the drawings is merely an example, and the dimensional ratio and the like do not indicate an actual state.

The metal foil mesh member 10 for screen printing which concerns on Embodiment 1 consists of metal foils used integrally with resin which forms a printing pattern. In the metal foil mesh member 10 for screen printing, a plurality of openings 12 are arranged in one direction in a line pattern portion. Y when the opening width of the opening 12 along one direction is Y, a rib when cut in the thickness direction along one direction of a rib 11 made of metal foil sandwiched between two openings 12 aligned along one direction Let A be a cross-sectional area of 11. In this case, the opening width Y is 10 μm to 39 μm. In addition, the width C along one direction of the rib 11 is 30 μm or less. Furthermore, the cross-sectional area B of the rib 11 per unit length along one direction obtained by dividing the cross-sectional area A of the rib 11 by the pitch X is 3 (μm ² / μm) ≦ B (μm ² / μm) Satisfy the relation

According to the metal foil mesh member 10 for screen printing, the opening width Y of the opening 12 along one direction is 10 μm to 39 μm. Thus, when the printing pattern opening width W is set to an appropriate width in the case of a screen printing plate, the printing line width can be narrowed.
In addition, the width C along one direction of the rib 11 is 30 μm or less. This allows the conductive paste to pass under the rib 11 and under the next print pattern opening during screen printing. Therefore, disconnection of the printing thin line can be prevented, and stable printability can be realized.
Furthermore, the cross-sectional area B of the rib 11 per unit length satisfies the relational expression 3 (μm ² / μm) ≦ B (μm ² / μm). By this, the fall of the intensity | strength of the metal foil mesh member 10 for screen printings by having made it thin as mentioned above can be suppressed.
Further, fine line printing and printing with an average thickness of 15 μm or more of the electrodes are possible by the screen printing plate using the metal foil mesh member 10 for screen printing. Furthermore, it is possible to provide a metal foil mesh member for screen printing and a screen printing plate using the same, which has sufficient strength such that the screen printing plate is not easily broken during plate making and printing.

In addition, as shown in FIG.2 and FIG.3, the pitch X of the some opening part 12 arranged along one direction may be 65 micrometers or less. The thickness Z of the metal foil may be 5 μm or more and 20 μm or less.

Below, each member which comprises this metal foil mesh member 10 for screen printing is demonstrated.

<Metal foil>
The metal foil is not limited to a rolled metal foil, and may be a metal foil formed by electroforming.
In addition, the metal foil may include, for example, at least one selected from the group of stainless steel, titanium, a titanium alloy, nickel, a nickel alloy, copper, a copper alloy, and an aluminum alloy.

FIG. 10 is a schematic view showing the relationship between the line width of a line pattern obtained by a screen printing plate using metal foil mesh members of different thicknesses and the line width of the line pattern. The thickness Z of the metal foil is 5 μm or more and 20 μm or less. The lower limit of the thickness Z is 5 μm because, if the thickness is smaller than 5 μm, there is a concern that the metal foil mesh member 10 may be broken or broken during handling of the metal foil mesh member, and the handling is difficult. The upper limit of the thickness Z is 20 μm, as shown in FIG. 10, when the thickness Z of the metal foil mesh member 10 is 20 μm and 25 μm in each of the cases where the present inventors carried out the printing test, This is because the inventors have found that the thinner 20 μm is more suitable for thin line printing than the case where the thickness Z is 25 μm. Further, in consideration of the handleability of the metal foil mesh member 10, the thickness Z is desirably 10 μm or more and 20 μm or less.

<Aperture>
FIG. 12 is a plan view showing an outline of the metal foil mesh member 10 having the oval-shaped opening 12. FIG. 13 is a plan view of the metal foil mesh member 10 having the rectangular opening 12a. The planar shape of the opening is not limited to the oval shape in FIG. 12 or the rectangular shape in FIG. 13, but may be another shape such as an elliptical shape.
Also, the multiple openings 12 provided in the metal foil may be formed by chemical etching, mechanical drilling, or electroforming.
Table 2 shows the results of comparison of the respective characteristics in the case where the openings are formed in the metal foil by the chemical etching method and in the case where the openings are formed by the electroforming method.

In the case of the etching method, by using a rolled metal foil for the metal foil, there is an advantage that the strength of the material is increased and the variation in thickness of the metal foil is reduced. Further, by forming openings of different sizes in the photoresist coated on both sides of the metal foil and etching from both sides, the opening width of both sides can be controlled, and the taper shape of the openings can be controlled. Moreover, since a continuous process is possible by using roll-shaped metal foil, cost reduction is possible by mass production. On the other hand, when the etching process (side etching) is not advanced until the opening of the metal foil becomes wider than the photoresist opening width on the metal foil at the time of the etching process, the opening unevenness can not be suppressed. For this reason, the minimum opening diameter is such that the side etching amount is added to the resolution of the photoresist, and the minimum opening diameter is larger than that of electroforming. In addition, when the rolling process is repeated to obtain a thin foil, the material becomes hard and cracks and the like occur, so that the thin foil obtained is limited.

In the case of the electroforming method, since the resolution of the photoresist directly leads to the minimum opening diameter, the minimum opening diameter can be smaller than that of the etching method. In addition, the variation in the opening size is smaller than in the etching method. Furthermore, since the metal foil is formed bottom-up, a thinner foil can be obtained than the rolled foil. On the other hand, control of the tapered shape is more difficult than the etching method. Further, as described in Patent Document 1, since the electroforming does not go through the rolling process, it is inferior to the etching method in terms of thickness variation and strength. Furthermore, in the electroforming method, continuous processing can not be performed as in the etching method, and a batch method is used, which is inferior to the etching method in cost.
Note that each method has advantages and disadvantages, and any method may be used.

<About the rib width>
FIG. 11 is a schematic view showing a mechanism in which the conductive paste 43 does not reach under the rib 11 to the next print pattern opening 17 when the rib width C is too long, and a break occurs in the print pattern.
As shown in FIG. 11, when the rib width is too long, the paste can not fully get under the rib at the time of printing, and a printing defect occurs. In a printing test of a screen printing plate using a metal foil mesh member for screen printing using SUS301 rolled metal foil prepared by the present inventors, a printing defect (break) occurs with a rib width C of 30 μm on the printing surface side It was not. Therefore, the rib width C on the printing surface side is preferably 30 μm or less.
This allows the conductive paste to pass under the rib 11 and under the next print pattern opening during screen printing. Therefore, disconnection of the printing thin line can be prevented, and stable printability can be realized.

<Tensile strength of metal foil mesh member for screen printing>
Arrows 8 in FIGS. 12 and 13 indicate the direction of the weakest tensile strength when the metal foil mesh member 10 is processed into a screen printing plate and pulled from all directions. In the metal foil mesh member 10 in which a large number of openings 12 are arranged along one direction, the tensile strength of the arrow 8 in FIGS. 12 and 13 is the smallest. This is because the cross section of the metal foil perpendicular to the pulling direction 8 is smaller in the metal foil portion than in the other directions because the opening 12 is provided. Therefore, if the cross-sectional area per unit length of the rib 11 sandwiched between the two openings 12 is not large to a certain extent, the metal foil mesh member 10 may break during processing into a screen printing plate or during printing.

<Cross-sectional area of rib per unit length along one direction>
In the metal foil mesh member 10 for screen printing, as described above, the cross-sectional area B of the rib 11 per unit length along one direction obtained by dividing the cross-sectional area A of the rib 11 by the pitch X is 3 ( It is characterized in that the relational expression of μm ² / μm) ≦ B (μm ² / μm) is satisfied.
Regarding metal foil mesh members using a SUS301 rolled material, the present inventors processed metal foil mesh members having a rib cross section per unit length of 2.97 μm ² / μm along one direction into a screen printing plate. I found out what I could do. That is, when the cross-sectional area of a rib per unit length along one direction is 2.97 μm ² / μm, in a screen printing plate made of combination using a polyester wedge in a 450 mm square aluminum frame, the tension gauge STG-75NA It could be processed into a screen printing plate with a tension of 0.95 mm to 1.10 mm and the printing test could be conducted. Therefore, the lower limit of the cross-sectional area B of the rib 11 per unit length along one direction can be defined as 3 μm ² / μm.
By satisfying the above relational expression, it is possible to secure sufficient tensile strength even in the case of screen printing plate as well as thinning.

When the cross-sectional shape of the rib 11 is a rectangular shape such as a square or a rectangle, as shown in FIG. 3, the cross-sectional area A of the rib 11 sandwiched between the two openings 12 has a rib width C and a thickness of metal foil It is represented by the product C × Z with Z. The rib width C is represented by the difference (X−Y) between the pitch X and the opening width Y. Therefore, the cross-sectional area A of the rib 11 is represented by (X−Y) × Z.
In addition, although the cross-sectional shape of the rib 11 is not the said rectangular shape normally but a trapezoid shape and the shape which includes a curved surface in part, the said relational expression is applied also in this case.

<Method of manufacturing metal foil mesh member for screen printing>
The metal foil mesh member 10 for screen printing can be manufactured by an etching method, an electroforming method, etc. as mentioned above. In the etching method, furthermore, the opening 12 can be formed by etching from one side or both sides of the metal foil, for example. Etching may be appropriately performed according to the desired shape and area of the opening 12 and the distribution thereof. For example, a resist is applied to a metal foil, a plurality of openings are arranged in a desired size and arrangement, and exposure is performed using a mask on which a printed pattern is drawn, followed by development. Then, the metal foil of the part which opens an opening part is melt | dissolved by etching, and the mesh member for screen printing which opened the opening part in metal foil can be produced.
In addition, as a manufacturing method of the metal foil mesh member for screen printing, a manufacturing method is not limited to the etching to metal foil, For example, it is realizable also with the mechanical drilling process and the manufacturing method by electroforming.

<Screen printing version>
FIG. 4 is a plan view showing an outline of the screen printing plate 20 according to the first embodiment. FIG. 5 is an enlarged plan view of a line pattern portion of the screen printing plate 20 using the metal foil mesh member 10 of FIG. 4 as viewed from the squeegee side 47. FIG. 6 is an enlarged plan view of a line pattern portion of the screen printing plate 20 using the metal foil mesh member 10 of FIG. FIG. 7 is an enlarged sectional view showing a sectional structure of the screen printing plate 20 of FIG. 5 as viewed from the β-β direction. FIG. 8 is an enlarged cross-sectional view showing a cross-sectional structure of the screen printing plate 20 of FIG. 5 as viewed from the γ-γ direction.

In the screen printing plate 20, as shown in FIG. 4, the metal foil mesh member 10 for screen printing is disposed on a frame 22 made of aluminum via a polyester sheath 24. The polyester weir 24 is a mesh woven from polyester fine wires. Further, the aluminum frame 22 and the polyester cage 24 are bonded via the bonding portion 23. The polyester weir 24 and the metal foil mesh member 10 are bonded via the bonding portion 25. In the screen printing plate 20, the resin 26 covering the metal foil mesh member 10 for screen printing is removed along the printing pattern, and as shown in FIG. 5 and FIG. It has a print pattern opening 17 formed of a resin that forms a line pattern. The longitudinal direction of the opening 12 of the metal foil mesh member 10 and the line pattern may be orthogonal or may intersect at an angle.

<Metal foil mesh member>
Since the above-mentioned thing is used for the metal foil mesh member 10, the overlapping description is abbreviate | omitted.

<Resin>
The resin covers a plurality of openings 12 arranged along one direction, as shown in FIGS. 5 and 6. This resin is, for example, a photocured photosensitive emulsion. Although the resin is used to form the line pattern here, the line pattern may be formed of a metal formed by electroforming instead of the resin.

<Printed pattern opening>
The resin pattern 16 covering the opening 12 of the metal foil mesh member 10 is opened, and a printing pattern opening 17 having an opening width W is formed.
The opening area of the print pattern opening 17 is preferably 1375 μm ² or less. This enables the printed line width to be 40 μm or less.
The print pattern opening width W is 10 μm or more and 40 μm or less. The formation of the print pattern opening width W of 10 μm or less is difficult because the resolution of the resin is insufficient. Further, since the printing line width tends to be larger than the printing pattern opening width W, the printing pattern opening width W must be 40 μm or less in order to perform thin line printing with the printing line width of 39 μm or less. The printing pattern opening width W is desirably 35 μm or less because the conductive silver paste is printed and generally spreads by about 5 μm with respect to the printing pattern opening width W.

Assuming that the thickness of the resin is E, the print pattern opening width formed of the resin is W, and the thickness of the metal foil mesh member is Z, E ≧ 0.6 × Z and (Z + E) /W≦1.33. It is characterized by The total thickness (Z + E) is 10 μm to 45 μm, and the print pattern opening width W is 10 μm to 40 μm.

First, when the thickness E of the resin is too thin, the paste 43 can not sufficiently go under the rib 11, and a printing defect occurs (FIG. 11). In addition, when the thickness E of the resin is thinner than the thickness Z of the ribs 11 of the metal foil mesh member 10, the resin filled in the openings 12 of the metal foil mesh member when the metal foil mesh member 10 is coated with the resin 16. There is a problem that 16 is in a state of being recessed with respect to the printing surface side (FIG. 14). As a result, when printing is performed using this screen printing plate, the paste spreads in the direction perpendicular to one direction, that is, in the width direction from the concave gap on the printing surface side. And the printing line width will spread.

The present inventors have found that the depression on the printing surface side of the resin 16 can be reduced by increasing the thickness E of the resin 16. FIG. 14 shows the state of δ − in FIG. 5 around the printing pattern opening of the screen printing plate in which two types of resins showing different surface shapes are laminated on the opening 12 of the metal foil mesh member 10 multiple times. It is a SEM observation image of the cut surface from (delta) direction. In addition, in FIG. 14, in order to make the boundary line of the sequential laminated state intelligible, laminating is performed using two different types of resins. That is, the resins 16a, 16b, 16c, 16d, 16e, and 16f sequentially stacked at the boundary between two types of resins are shown. According to FIG. 14, when the resin thickness E of the resins 16a, 16b, 16c, etc. is small, the dent of the boundary line of the resin is large, and as the resin thickness E of the resins 16d, 16e, 16f, etc. becomes large, the dent of the boundary line It can be confirmed that the FIG. 15 is a schematic view showing the relationship between the total thickness (E + Z) of FIG. 14 and the amount of indentation on the printing surface side around the printing pattern opening 17. As shown in FIG. 15, when the metal foil mesh thickness is 25 μm, the total thickness (E + Z) at which the recess is 2 μm or less is 40 μm and E is 15 μm. When the metal foil mesh thickness is 20 μm, the total thickness (E + Z) at which the recess is 2 μm or less is 32 μm and the resin thickness E is 12 μm. Further, as the thickness Z of the metal foil mesh member decreases, the resin thickness E at which the recess is 2 μm or less also decreases, and the ratio (E / Z) is approximately 0.6. Therefore, in order to suppress the spread of the printing line width, the condition of E ≧ 0.6 * Z is preferable in order to make the depression of the resin 2 μm or less.

In addition, when the total (Z + E) of the metal foil mesh member and the thickness of the resin and the aspect ratio (Z + E) / W of the printing pattern opening width W is too large, the printed pattern opening where the paste is formed by the metal foil mesh and the resin It is not possible to pass through 17, and printing defects occur.
In the printing test conducted by the present inventors, no printing failure occurred at the above-mentioned aspect ratio 1.33, but printing failure occurred at the aspect ratio 1.60. Therefore, the aspect ratio (Z + E) / W is preferably 1.33 or less.

The thickness E of the metal foil is 5 μm or more and 20 μm or less, the total thickness (Z + E) is 10 μm or more and 45 μm or less, and E ≧ 0.6 × Z. It becomes 8 micrometers or more and 40 micrometers or less.

<Method of producing screen printing plate>
This screen printing plate can be produced, for example, as follows. For example, after a resin (photosensitive emulsion) is coated on the entire surface of the metal foil, the portion corresponding to the line pattern to be opened is covered with a mask, and the portion other than the portion covered by the mask is exposed. The resin (photosensitive emulsion) in the exposed area is cured, and the resin (photosensitive emulsion) in the opening part of the area covered with the mask is removed to prepare a screen printing plate. In addition, the said manufacturing method is an illustration, It is not limited to this.

<Solar cell>
FIG. 16 is a plan view showing an outline of a crystalline silicon solar cell 30 according to the first embodiment. The solar cell 30 has a silicon wafer 32 which is a solar cell substrate, and finger electrodes 34 and bus bar electrodes 36 for collecting electron-hole pairs generated by the reception of sunlight on the silicon wafer 32. The finger electrode 34 is, for example, a conductive pattern having a width of 45 μm to 100 μm and a length of 150 mm to 160 mm. The bus bar electrode 36 is, for example, a conductive pattern having a width of 1 mm or more and 2 mm or less and a length of 150 mm or more and 160 mm or less extending in a direction orthogonal to the finger electrode 34. The finger electrodes 34 and the bus bar electrodes 36 are, for example, silver electrodes.
Although the electrode pattern on the front surface side of the solar cell is described above, the electrode pattern on the back surface side of the solar cell may also be formed.

<About the manufacturing method of the solar cell by screen printing>
FIG. 17 is a schematic view showing an outline of a method of manufacturing a solar cell by screen printing.
(1) The screen printing plate 20 and the solar cell substrate 46 to be printed are prepared. The squeegee surface 47 of the screen printing plate 20 is a vertical upper surface, and the printing surface 48 is a vertical lower surface. The printing surface 48 is faced to a solar cell substrate 46 which is a printing target to be screen-printed.
(2) Next, the paste 43 is placed on the squeegee surface, and the squeegee 42 is moved from the left to the right in FIG. 17 to fill the paste 43 in the printing pattern opening 17 of the screen printing plate. The paste 43 is attached to 46. After the squeegee 42 passes, the screen printing plate 20 and the solar cell substrate 46 are separated due to the tension of the screen printing plate 20. On the other hand, the paste 43 remains on the solar cell substrate 46.
By the above, screen printing is performed, and the paste 43 corresponding to the arrangement of the printing pattern openings 17 of the screen printing plate 20 is printed. Thereafter, the paste 43 having irregularities derived from the arrangement of the print pattern openings 17 undergoes a leveling process, and finger electrodes are formed on the solar cell substrate 46. A solar cell is obtained by this.

(Example)
Hereinafter, the present invention will be described in more detail by way of examples, but the following examples are not of the nature to limit the present invention, and may be appropriately modified and implemented within the scope which can conform to the above and below. And all are included in the technical scope of the present invention.

In the experiment shown in FIG. 9, the present inventors speculated that fine line printing with a printing line width of 39 μm or less can be performed by setting the average opening area of the printing pattern opening of the screen printing plate to 1375 μm ² or less. Therefore, in order to realize thin line printing with a printed line width of 39 μm or less, the metal foil mesh member described in the present disclosure was manufactured using an Ni--Co alloy by electroforming. The cross-sectional area of the rib per unit length of the opening installed along one direction is 3.60 μm ² / μm to 4.34 μm ² / μm, the opening pitch X is 40 μm to 65 μm, and the opening width Y is 24 μm The thickness Z of the metal foil is 15 μm or more. FIG. 18 shows an optical micrograph of an opening specification with a pitch X of 40 μm and an opening width Y of 24 μm at the opening of the manufactured metal foil mesh member, and FIG. 19 shows a cross-sectional SEM observation photograph of a rib of the same opening.

Using this metal foil mesh member, a screen printing plate having an emulsion thickness of 14 μm and a printing pattern width of 29 μm and 32 μm was produced. Printing was performed using a conductive silver paste (FS41 manufactured by Heraeus) using the produced printing plate, and the shape of the printed paste was measured with a microscope (manufactured by Olympus Corporation: model DSX500).
The result of printing is shown in FIG. As shown in FIG. 9, the print line width tends to be smaller as the opening area is smaller, and the print line width of 40 μm or less can be realized by setting the average opening area of the print pattern opening 17 to 1375 μm ² or less. did it. The printed line width is 34.7 μm, the average height is 21.6 μm, and the aspect ratio is 0.63 (averaged). The pitch X of the openings 12 is 40 μm, the opening width Y is 24 μm, and the printed pattern opening width W is 28 μm. The μ scope observation image of the finger electrode of height ÷ printed line width) is shown in FIG.

By using the metal foil mesh member and the screen printing plate according to the above example, a line pattern having a printing line width of 39 μm or less, an average height of 20 μm or more, and an aspect ratio of 0.5 or more could be realized by screen printing. Moreover, by using this screen printing plate, thinning of the surface silver electrode of the solar cell is realized and the conversion efficiency of the solar cell is improved, and in addition, the printing with the high aspect ratio in one-time printing By replacing printing twice, it is possible to reduce the solar cell manufacturing process and achieve cost reduction.

Note that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and the respective embodiments and / or examples. The effects of the embodiment can be exhibited.

According to the metal foil mesh member of the present invention, thin screen printing with a printing line width of 39 μm or less is possible by the screen printing plate using the same, and sufficient strength that the screen printing plate does not easily break during plate making and printing It is possible to provide a metal foil mesh member for screen printing and a screen printing plate using the same.

2 finger electrode pattern 4 bus bar electrode pattern 8 stress 9 test piece 10 metal foil mesh member 11 for screen printing rib 12, 12a opening (hole, oval, rectangle)
16, 16a, 16b, 16c, 16d, 16e, 16f resin (photosensitive emulsion)
17 printing pattern opening 20 screen printing plate 22 aluminum frame 23 adhesion part 24 of aluminum frame and polyester weir 25 polyester bond 25 adhesion section of metal foil mesh member and polyester weir 26 resin coated part (metal foil mesh member)
DESCRIPTION OF SYMBOLS 30 solar cell 32 silicon wafer 34 finger electrode 36 bus-bar electrode 42 squeegee 44 silver paste 44 scraper 46 Si wafer 47 squeegee surface 48 printing surface 50 screen printing plate 51 wire 52 opening 56 resin (photosensitive emulsion)

Claims (9)

It is a metal foil mesh member for screen printing which consists of metal foils used by making it integral with resin which forms a printing pattern,
The opening width along the one direction of the plurality of openings arranged at the pitch X along the one direction of the metal foil mesh member for screen printing is Y, which is sandwiched by the two openings aligned along the one direction When the cross-sectional area of the rib when cut in the thickness direction along the one direction of the rib made of the metal foil is A,
The opening width Y is 10 μm to 39 μm, and
The width C of the rib along the one direction is 30 μm or less,
The cross-sectional area B of the rib per unit length along the one direction obtained by dividing the cross-sectional area A of the rib by the pitch X is 3 (μm ² / μm) ≦ B (μm ² / μm) The metal foil mesh member for screen printing which satisfy | fills the relational expression of 5.). The pitch X is 65 μm or less,
The metal foil mesh member for screen printing of Claim 1 whose thickness Z of the said metal foil is five to 20 micrometer. The metal foil mesh member for screen printing according to claim 1, wherein the metal foil is electroformed. A screen printing plate comprising the metal foil mesh member for screen printing according to claim 1. A resin covering the plurality of openings arranged along the one direction of the metal foil mesh member for screen printing;
A print pattern comprising a plurality of print pattern openings in which the longitudinal direction is the one direction and the resin covering the opening is opened with a print pattern opening width W intersecting the one direction;
The screen printing plate of claim 4, further comprising: The screen printing plate according to claim 5, wherein an average area of the plurality of printing pattern openings is 1375 μm ² or less. Assuming that the thickness of the resin is E and the thickness of the metal foil mesh member for screen printing is Z, the relational expression of E0.60.6 × Z and (Z + E) /W≦1.33 is satisfied,
The total thickness (Z + E) is 10 μm or more and 45 μm or less,
The screen printing plate according to claim 5, wherein the printing pattern opening width W is 10 μm or more and 40 μm or less. The screen printing plate according to claim 5, which is used for electrode wiring for solar cells. A step of preparing the screen printing plate according to claim 5 and a solar cell substrate which is an object to be printed;
Performing screen printing using the screen printing plate to form finger electrodes on the solar cell substrate;
A method of manufacturing a solar cell, including:

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