JP2014067791A - Method for manufacturing printed wiring board - Google Patents

Abstract

A printed wiring board having high through-hole reliability is obtained.
A step of forming a through hole in a laminated substrate made of insulating resin, a step of providing a metal plating layer on the surface of the laminated substrate and an inner wall surface of the through hole, and a step of forming a metal plating layer on the metal plating layer Forming an electrodeposition resist film by an electrodeposition process; removing the electrodeposition resist film on the surface of the multilayer substrate by a surface polishing process to expose the metal plating layer; and soft etching the metal plating layer The step of thinning, the step of removing the electrodeposition resist film on the metal plating layer on the inner wall surface of the through hole, and the step of etching the thinned metal plating layer to form a surface wiring pattern. Manufactures printed wiring boards.
[Selection] Figure 2

Description

  The present invention relates to a method for manufacturing a printed wiring board in which a through hole is formed together with a wiring pattern of a precise fine circuit on the printed wiring board, and in particular, manufacturing a printed wiring board with high reliability of electrical connection of the through hole plating. It is about the method.

  In the conventional printed wiring board manufacturing method, when manufacturing a printed wiring board in which a precise fine circuit wiring pattern and a through hole exist together, drilling is performed from the surface of the insulating substrate with a through hole. Form. Thereafter, a copper plating process is performed on the through hole wall and the substrate surface to form a plated through hole structure in which the front and back surfaces of the insulating substrate and the inner layer are electrically connected by the copper plating film on the through hole wall. Next, it progresses to a circuit formation process, the photosensitive dry film resist is laminated on the surface of a copper plating film, and the pattern picture is exposed. Next, the resist for etching the copper is dissolved and removed by development. Next, the exposed copper portion is etched to form a circuit wiring pattern.

  Here, when forming the wiring pattern of the fine circuit on the printed wiring board using the subtractive method, it is necessary to reduce the thickness of the metal plating layer on the formation surface of the wiring pattern of the fine circuit on the printed wiring board. The reason is to secure an etching factor for forming the circuit wiring pattern. When a circuit is formed using a subtractive method with a thick metal plating layer, the etching factor deteriorates and the circuit shape is reduced. This is because not only cannot be ensured, but also a short circuit may occur.

Conventionally, as a method of forming a thin metal plating layer,
(1) a method of chemically dissolving and forming a thin metal plating layer;
(2) There is a method of physically cutting the metal plating layer by mechanical polishing to form a thin metal plating layer,
Both methods are performed after the process of forming a copper plating layer in the through hole.

(Formation of fine circuit wiring pattern by subtractive method)
In the subtractive method, it is difficult to coexist the through hole and the wiring pattern of the fine circuit. The reason is that there is a trade-off between securing the plating thickness in the through hole and reducing the thickness of the metal plating layer for forming the thin wire circuit.

  There are chemical methods and physical methods for thinning the metal plating layer, but each has the following problems. In other words, when the metal plating layer is thinned by a chemical method, the flow of the liquid into the through hole is faster and the metal plating layer on the wall surface of the through hole hole is dissolved excessively than the surface layer, so that the metal plating in the through hole is There is a problem that it is difficult to keep the layer thickness thick.

  On the other hand, when the metal plating layer is thinned by mechanical polishing using a physical method, the metal plating layer of the through-hole 追 従 is excessively polished and cut in the form of following the through-hole during mechanical polishing. There is a problem that the reliability of the electrical connection at the base of the hall is lowered.

  In this way, in both chemical and physical methods, the thinning process of the metal plating layer required to form a fine circuit wiring pattern using the subtractive method is the reliability of the electrical connection of the through hole. It is difficult to make it compatible with the conditions for ensuring the above.

  Therefore, conventionally, as in Patent Document 1 and Patent Document 2, after filling a through hole with a hole filling resin such as a thermosetting insulating resin or a conductive resin, the through hole is sealed, and then the surface of the insulating substrate is sealed. A technique for thinning the metal plating layer has been used.

JP 2002-016357 A JP 2003-273488 A

  In the techniques of Patent Literature 1 and Patent Literature 2, the filling resin / paste is filled in the through hole, and the metal plating layer thickness is adjusted in a state where the through hole is sealed. Since the metal plating layer in the through hole is protected by hole filling resin or paste, the metal plating layer is maintained without being affected by the etching solution, and only the metal plating layer on the surface of the insulating substrate can be thinned. Is possible.

  However, when the hole filling resin is used in this conventional technique, the hole filling resin cannot be removed after curing, and thus there is a problem that it is impossible to connect the terminal pin of the mounting component by inserting it into the through hole. .

  In addition, when using the paste in this conventional technique, the paste can be removed in a later process, but in order to remove the paste that is completely sealed in the through hole, the paste is placed in the through hole. There is a problem that becomes a risk of causing a connection failure of the mounted parts by remaining.

  Further, in these conventional techniques, after the metal plating layer is thinned by etching, it is necessary to remove the portion of the hole filling resin / paste protruding from the substrate surface by polishing. The height of the protrusion is 20 to 30 μm, and therefore a certain amount of cutting and polishing treatment is required. By performing the cutting and polishing treatment, the metal plating layer on the surface of the insulating substrate is further thinned, and there is a problem that the thickness of the metal plating layer on the surface of the insulating substrate varies due to the variation in polishing. .

  It is an object of the present invention to provide a method for manufacturing a printed wiring board that solves such problems and obtains a printed wiring board having high through-hole reliability.

  In order to solve the above-mentioned problems, the present invention provides a step of forming a through hole in a laminated substrate made of an insulating resin, and a step of providing a metal plating layer on the surface of the laminated substrate and the inner wall surface of the through hole. And a step of forming an electrodeposition resist film on the metal plating layer by an electrodeposition process; a step of removing the electrodeposition resist film on the surface of the laminated substrate by a surface polishing process to expose the metal plating layer; A step of thinning the metal plating layer by soft etching; a step of removing the electrodeposition resist film on the metal plating layer on the inner wall surface of the through hole; and etching the thinned metal plating layer to obtain a surface layer. And a process for forming a wiring pattern.

Further, the present invention is a method for producing the above printed wiring board, wherein the step of forming an electrodeposition resist film by electrodeposition treatment on the metal plating layer forms a positive photosensitive electrodeposition resist film, Next, the step of irradiating the positive photosensitive electrodeposition resist film with ultraviolet rays from a direction perpendicular to the surface of the multilayer substrate, and then the positive photosensitive electrodeposition resist film on the surface of the multilayer substrate Is a surface polishing process to expose the metal plating layer.

  Moreover, this invention is a manufacturing method of said printed wiring board, Comprising: The said through-hole was formed in the said laminated substrate with the drill, It is a manufacturing method of the printed wiring board characterized by the above-mentioned.

  The present invention is also a method for producing a printed wiring board as described above, wherein the laminated substrate is formed by laminating a prepreg and a metal foil on the surface of an inner layer substrate. is there.

  Moreover, this invention is a manufacturing method of said printed wiring board, Comprising: The said laminated substrate provides the copper foil with resin on the surface of an inner layer board | substrate, It is a manufacturing method of the printed wiring board characterized by the above-mentioned.

  Moreover, this invention is a manufacturing method of said printed wiring board, Comprising: The process of drilling a via-hole pilot hole by laser drilling to the said insulating resin of the said laminated substrate, and the process of filling this via-hole pilot hole with metal plating This is a method for manufacturing a printed wiring board.

  According to the method for producing a printed wiring board of the present invention, the electrodeposition resist film formed on the surface of the multilayer substrate is a 7 μm film, and surface polishing with a polishing of about 10 μm is possible. When removing the electrodeposition resist film on both surfaces by polishing the surface, it is possible to leave the electrodeposition resist film at the ridge portion of the through-hole without removing it, and there is an effect that a highly reliable through hole can be formed.

  Further, a positive photosensitive electrodeposition resist film is used as the electrodeposition resist film, and after irradiating ultraviolet rays from a direction perpendicular to the surface of the multilayer substrate, the positive photosensitive electrodeposition resist film on the surface of the multilayer substrate is used. If removed by the surface polishing treatment, there is an effect that the electrodeposition resist film covering the through-hole plating layer in the through hole can be hardly formed at the flange portion of the through hole.

It is process sectional drawing of the manufacturing method of the printed wiring board which shows the Example of this invention (the 1). It is process sectional drawing of the manufacturing method of the printed wiring board which shows the Example of this invention (the 2). It is process sectional drawing of the manufacturing method of the printed wiring board which shows the Example of this invention (the 3).

  Below, the manufacturing method of the printed wiring board by embodiment of this invention is demonstrated using FIGS. 1-3.

(Process 1)
First, an inner layer substrate 2 in which a copper foil having a thickness of 12 μm to 70 μm is bonded to the insulating substrate 1 is manufactured. Here, as the insulating substrate 1, a substrate of an insulating resin with a reinforcing material is used. That is, a glass fiber-containing epoxy resin material, a glass fiber-containing bismaleimide-triazine resin (hereinafter referred to as BT resin) material, a glass fiber-containing polyimide resin material, or a glass fiber-containing PPE resin material can be used. As a reinforcing material for the insulating substrate 1, the following materials can be used instead of glass fibers. That is, an aramid nonwoven fabric, an aramid fiber, and a polyester fiber can be used.

(Process 2)
Next, the copper foil of the inner layer substrate 2 is patterned by etching to form an inner layer wiring pattern 3 as shown in FIG.

(Process 3)
Next, the surface of the inner layer wiring pattern 3 is subjected to perhydrosulfuric acid-based soft etching, CZ treatment using a formic acid solution (for example, “Meck Etch Bond” manufactured by MEC Co., Ltd.), or blackening treatment by oxidation-reduction treatment. , Roughening treatment is performed so that the maximum roughness (Rmax) is 0.1 to 10 μm.

(Process 4)
Similar to the inner layer substrate 2, a second inner layer substrate 4 is formed.

(Process 5)
Next, as shown in FIG. 1B, in order from the upper layer, a first metal foil 5 such as a copper foil or an aluminum foil having a thickness of 12 μm, a first prepreg 6, an inner layer substrate 2, A laminated material in which the second prepreg 7, the second inner layer substrate 4, the third prepreg 8, and the second metal foil 9 are stacked thereunder is formed.

  Here, instead of the combination of the prepreg and the metal foil, a resin-attached metal foil can be used.

(Step 6)
Next, as shown in FIG. 1 (c), this laminated material is heated and pressurized with a lamination press to melt and flow out the resin material of the prepreg, and each material of the laminated material is bonded with the molten resin. Accordingly, the first metal foil 5, the first insulating resin layer 6a, the first inner layer substrate 2, the second insulating resin layer 7a, the second inner layer substrate 4, the first metal foil 5, the first insulating resin layer 6a, and the second inner layer substrate 4 are sequentially formed from the upper layer to the lower layer. A laminated substrate 10 in which the three insulating resin layers 8a and the second metal foil 9 are laminated is formed. Here, the thickness of the first insulating resin layer 6a and the third insulating resin layer 8a is preferably about 30 to 90 μm.

(Step 7)
Next, as shown in FIG. 1D, the first metal foil 5 and the second metal foil 9 of the multilayer substrate 10 are etched and removed. In this etching process, when the first metal foil 5 and the second metal foil 9 are copper foils, etching is performed using an etchant such as a ferric chloride aqueous solution.

(Modification 1)
As a first modification of the step 7, instead of etching the entire surface of the first metal foil 5 and the second metal foil 9, the first metal foil 5 and the second metal foil 5 are etched by etching at a position where the via hole prepared hole 11 is formed. The opening may be formed in the metal foil 9 larger than the via hole pilot hole 11.

(Modification 2)
As modification 2 of this process 7, the 1st metal foil 5 and the 2nd metal foil 9 are formed with thin copper foil, for example, 9 micrometers foil, and in process 7, the 1st metal foil 5 and the 2nd The surface of the metal foil 9 is roughened and blackened, and in the subsequent step 8, the first metal foil 5 and the second metal foil 9 of the thin copper foil are penetrated with a laser beam and a via hole pilot hole is formed. 11 may be formed, and then the through hole 12 may be formed in step 9. After the via hole pilot hole 11 is formed, the blackened surfaces of the surfaces of the first metal foil 5 and the second metal foil 9 are made smooth by soft etching, and then the processes after step 10 are performed.

(Process 8)
Next, as shown in FIG. 1E, under the via hole reaching the inner layer wiring pattern 3 by irradiating a carbon dioxide laser beam or a YAG laser beam from the outer surfaces of the second insulating resin layer 6a and the third insulating resin layer 8a. Hole 11 is laser drilled. This via-hole prepared hole 11 is a prepared hole for forming a via-hole plating 11 a that electrically connects the inner layer wiring pattern 3 to the upper and lower wiring patterns 15 of the multilayer substrate 10 in a subsequent process. The shape of the via hole prepared hole 11 is, for example, an outer layer side diameter of 80 μm, an inner layer side hole bottom diameter of 50 μm, and an interlayer thickness of the first insulating resin layer 6a and the third insulating resin layer 8a formed to be 30 to 90 μm. To do.

(Step 9)
Next, the through hole 12 is formed by drilling the laminated substrate 10 with a drill.

(Process 10)
Next, the surface of the multilayer substrate 10 and the wall surface of the through hole 12 are roughened. Here, if the via hole pilot hole 11 is formed with a laser beam in step 8, a thin resin film may remain at the bottom of the via hole pilot hole 11. In this case, the resin is swollen with strong alkali, and then chromic acid is used. And desmear treatment that decomposes and removes the resin using an oxidizing agent such as a permanganate aqueous solution. Further, the resin film remaining on the bottom of the hole may be removed by sandblasting with an abrasive or plasma treatment.

  The roughening treatment of the wall surface of the through-hole 12 of the laminated substrate 10 is performed by oxidizing an aqueous solution of chromic acid or permanganate when a thermosetting resin or a thermoplastic resin is used for the insulating substrate 1 of the inner layer substrates 2 and 4. A wet process such as surface roughening with an agent and a dry process such as plasma or ashing are effective.

(Step 11)
Next, plating catalyst application and electroless copper plating are performed on the wall surface of the via-hole prepared hole 11, the wall surface of the through-hole 12, and the surface of the multilayer substrate to form a plating base conductive layer. Next, electrolytic copper plating is performed to form a through-hole plating layer 12a on the wall surface of the through-hole 12 as shown in FIG. 2 (f), and via-hole pilot holes are formed on the plating base conductive layers on both sides of the multilayer substrate 10. 11 is filled with copper via-hole plating 11a, and a copper metal plating layer 13 is formed on the entire surface of both surfaces.

(Step 12)
Next, as shown in FIG. 2G, a positive photosensitive electrodeposition resist film 14 is formed on the entire surface of the upper and lower metal plating layers 13 of the multilayer substrate 10 and the surface of the through hole plating layer 12 a in the through hole 12. A thickness of 7 μm is formed by electrodeposition. Next, the positive photosensitive electrodeposition resist film 14 is dried by heating at 80 ° C. for 10 minutes.

(Step 13)
Next, ultraviolet light is exposed perpendicularly to the surface from the upper and lower surfaces of the laminated substrate 10 to expose the upper and lower positive photosensitive electrodeposition resist films 14. By this ultraviolet light exposure, the chemical bond portions of the molecules of the positive photosensitive electrodeposition resist film 14 on the upper and lower surfaces of the multilayer substrate 10 are cut off, and the hardness of the positive photosensitive electrodeposition resist film 14 is softened. At this time, ultraviolet rays perpendicular to the upper and lower surfaces of the multilayer substrate 10 are applied to the positive photosensitive electrodeposition resist film 14 covering the through-hole plating layer 12 a in the through hole 12 at a certain depth from the surface side of the multilayer substrate 10. No more exposure. As a result, ultraviolet rays are not exposed to the molecules of the positive photosensitive electrodeposition resist film 14 in the deep part of the through hole 12, and the molecules of the positive photosensitive electrodeposition resist film 14 in the through hole 12 have strong chemical bonds. Bonded and hard hardness is maintained.

(Step 14)
Next, as shown in FIG. 2 (h), a positive photosensitive electrodeposition resist film 14 covering the surface of the laminated substrate 10 is formed on the surface with a polishing buff (fiber impregnated with silicon carbide or the like). Surface polishing is performed with the polished polishing roll. As a result, the positive photosensitive electrodeposition resist films 14 on the upper and lower surfaces of the laminated substrate 10 that have been softened by being exposed to ultraviolet rays are removed by mechanical polishing. At that time, the positive photosensitive electrodeposition resist film 14 covering the through-hole plating layer 12a in the through-hole 12 is not exposed to ultraviolet rays, so that it is kept in a hard state, and is used as an abrasive for buffing. Since it does not contact directly, it remains without being removed. Further, the positive type photosensitive electrodeposition resist film 14 covering the flange portion of the through hole 12 near the film covering the through hole plating layer 12a of the through hole 12 remains without being removed by this mechanical polishing.

  That is, according to the present embodiment, the positive photosensitive electrodeposition resist film 14 covering the through-hole plating layer 12a in the through-hole 12 is hard even at the ridge portion of the through-hole 12, so When the type photosensitive electrodeposition resist film 14 is removed by polishing the surface, the positive type photosensitive electrodeposition resist film 14 at the end of the through hole 12 can be left without being removed, and a highly reliable through hole can be formed. There is an effect that can be formed.

(Step 15)
Next, by heating at 160 ° C. for 40 minutes, the ridges of the through holes 12 and the positive photosensitive electrodeposition resist film 14 remaining inside are cured by heating. Thereby, there is an effect that the hardness of the positive photosensitive electrodeposition resist film 14 as an etching resist in the flange portion of the through hole 12 is enhanced.

(Step 16)
Next, as shown in FIG. 2 (i), the metal on the surface of the laminated substrate 10 is obtained by soft etching using a ferric chloride solution, sodium persulfate, or an etching solution of hydrogen peroxide / sulfuric acid solution. The plating layer 13 is soft etched to reduce the thickness. The thickness of the metal plating layer 13 to be removed by this soft etching is controlled by the etching temperature, time, or etching solution concentration. During this soft etching, the through-hole plating layer 12a in the through-hole 12 is protected by the positive photosensitive electrodeposition resist film 14 up to the flange portion of the through-hole 12, so that the through-hole plating layer 12a in the through-hole 12 is protected. The entire hole plating layer 12a remains without being etched, and a good through-hole plating structure is formed.

(Step 17)
Next, as shown in FIG. 3J, the positive photosensitive electrodeposition resist film 14 covering the through-hole plating layer 12a in the through hole 12 of the multilayer substrate 10 is removed.

(Step 18)
Next, a photosensitive resist, for example, an etching resist of a dry film is pasted on the metal plating layers 13 on both surfaces of the multilayer substrate 10 by roll lamination, and the etching resist is exposed and developed, so that the portions other than the surface wiring pattern 15 portions are exposed. Expose the copper plating layer.

  Next, as shown in FIG. 3 (k), the copper metal plating layer 13 exposed from the etching resist is removed by etching with an etchant such as ferric chloride aqueous solution to form a surface wiring pattern 15 Then, the etching resist is peeled off.

(Step 19)
Next, as shown in FIG. 3 (l), a photosensitive solder resist is formed on both surfaces of the laminated substrate 10, exposed and developed, and then the solder resist pattern 16 is formed by heating and curing.

In addition, this invention is not limited to said embodiment, In the process 12, the electrodeposition resist film which does not have photosensitivity on the whole surface of the metal plating layer 13, and the surface of the through-hole plating layer 12a in the through-hole 12 May be formed. In that case, a printed wiring board is manufactured in a process that omits the process 13 of irradiating the electrodeposition resist with ultraviolet rays.

  Further, the number of inner layer substrates is not limited to two, and one or three or more inner layer substrates may be used, and an inner layer substrate may be used as the outermost layer of the laminated substrate 10. In addition to the method of forming the laminated substrate 10 by stacking the inner layer substrate and the prepreg and heating and pressing with a lamination press, the laminated substrate 10 is formed by laminating a copper foil with resin on the inner layer substrate and building up. It may be formed. Furthermore, the laminated substrate 10 may be formed by separating the support substrate from the insulating resin layer formed by building up on the support plate. Moreover, the through-hole 12 formed in the laminated substrate 10 may be formed by laser drilling other than forming with a drill.

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2, 4 ... Inner layer board 3 ... Inner layer wiring pattern 5, 9 ... Metal foil 6, 7, 8 ... Prepreg 6a, 7a, 8a ... Insulating resin layer 10 ... Laminated substrate 11 ... via hole pilot hole 11a ... via hole plating 12 ... through hole 12a ... through hole plating layer 13 ... metal plating layer 14 ... positive photosensitive electrodeposition resist Film 15 ... Surface wiring pattern 16 ... Solder resist pattern

Claims (6)

  A step of forming a through hole in a laminated substrate made of insulating resin, a step of providing a metal plating layer on the surface of the laminated substrate and an inner wall surface of the through hole, and an electrodeposition treatment on the metal plating layer A step of forming an electrodeposition resist film, a step of removing the electrodeposition resist film on the surface of the multilayer substrate by a surface polishing process to expose the metal plating layer, and thinning the metal plating layer by soft etching And a step of removing the electrodeposition resist film on the metal plating layer on the inner wall surface of the through hole, and a step of etching the thinned metal plating layer to form a surface wiring pattern. A method for manufacturing a printed wiring board.   The method for producing a printed wiring board according to claim 1, wherein the step of forming an electrodeposition resist film by electrodeposition treatment on the metal plating layer forms a positive photosensitive electrodeposition resist film, A step of irradiating the positive photosensitive electrodeposition resist film with ultraviolet rays from a direction perpendicular to the surface of the multilayer substrate, and then polishing the positive photosensitive electrodeposition resist film on the surface of the multilayer substrate A method for producing a printed wiring board, wherein the metal plating layer is exposed by removal by treatment.   The method for manufacturing a printed wiring board according to claim 1, wherein the through hole is formed in the laminated substrate by a drill.   4. The printed wiring board manufacturing method according to claim 1, wherein the laminated substrate is formed by laminating a prepreg and a metal foil on a surface of an inner layer substrate. 5. A manufacturing method of a board.   4. The method of manufacturing a printed wiring board according to claim 1, wherein the laminated substrate is provided with a resin-coated copper foil on a surface of an inner layer substrate. 5. Production method.   It is a manufacturing method of the printed wiring board as described in any one of Claims 1 thru | or 5, Comprising: The process of drilling a via-hole pilot hole by laser drilling to the said insulating resin of the said laminated substrate, and this via-hole pilot hole by metal plating A method for manufacturing a printed wiring board, comprising a step of filling.

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