JP2002305381A - Printed wiring board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a printed wiring board capable of forming a fine conductor pattern of good shape, without degradation in productivity. SOLUTION: A conductor layer transfer sheet 31 is used where a transfer copper foil 32 is releasably held on a carrier copper foil 33 which is thicker than it. The transfer copper foil 32 is transferred and pasted to at least one surface of an insulating base material 4 through a pre-preg 34, to form a copper base material layer 6. A mask 11 is formed on the copper base material layer 6, and copper plating layers 7 and 8 are formed at a place exposed from its opening part 12. Then etching is performed after the mask 11 is removed, and the copper base material 6 is removed to separate conductor patterns 2b from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printed wiring board and a method for manufacturing the same.

[0002]

2. Description of the Related Art Printed wiring board manufacturing methods are broadly classified into a subtractive process and an additive process. The subtractive method is also called an etching method, and is characterized by chemically corroding the surface copper foil of the copper-clad laminate. Here, an example of a method of manufacturing the multilayer printed wiring board 41 using the subtractive method will be briefly described with reference to FIGS.

[0003] First, a copper-clad laminate 44 is prepared and etched to form inner layer conductor patterns 53 on both surfaces of an insulating base material 42. Then, a copper foil 55 having a thickness of about 12 μm is laminated and attached to both surfaces of the insulating base material 42 via the prepreg 54 (see FIG. 10). A hole 45 for forming a through-hole is formed at a predetermined position of the insulating base material 42 to which the copper foil 55 is stuck by drilling or the like. Copper foil 55
Then, a thin copper plating layer 47 is formed by electroless copper plating on the entire copper base layer 46 and the inner wall surface of the through-hole forming hole 45 (see FIG. 11). After such a panel plating step, a mask 4 is formed on the thin copper plating layer 47.
8 is formed. Then, a thick copper plating layer 50 is formed by electrolytic copper plating in a portion exposed from the opening 49 of the mask 48 (see FIG. 12). After such a pattern plating step, an etching resist 56 is formed on the thick copper plating layer 50 by solder plating or the like, and the mask 48 is peeled off (see FIG. 13). Then, etching is performed in this state. This etching removes the thinned copper plating layer 47 and the copper base layer 46 and removes the outer conductor pattern 5.
Divide the two. Finally, if the etching resist 56 is peeled off, the desired multilayer printed wiring board 41 is completed (see FIG. 14).

[0004]

However, in the above-mentioned conventional manufacturing method, a fine pattern having a good shape cannot be accurately formed, and the bottom is considerably longer than the top in terms of etching characteristics. It is easy to become the outer conductor pattern 52 having a flared shape. Therefore, it is difficult to form a pattern of a portion (for example, a bonding pad portion) where fineness and high precision are required.

Therefore, in place of the copper foil 55, a thickness of 1
A countermeasure of forming the copper base layer 46 using an extremely thin copper foil of 0 μm or less can be considered. This is because the thickness to be removed by etching in the conductor pattern dividing step can be reduced. Accordingly, the outer conductor pattern 52 formed by the division is less likely to have a flared shape.

However, since the copper foil is extremely thin, it is easily deformed or damaged. Therefore, when pattern formation is performed using a deformed copper foil, high yield and high reliability may not be realized. Therefore, in order to avoid such deformation and the like, it is necessary to carefully handle the copper foil during handling, which naturally lowers productivity.

The present invention has been made in view of the above problems, and has as its object to manufacture a printed wiring board capable of forming a fine conductor pattern having a good shape without a decrease in productivity. It is to provide a method and the like.

[0008]

According to a first aspect of the present invention, in a method of manufacturing a printed wiring board having a conductor pattern, a transfer copper foil is thicker than the transfer copper foil. Using a conductive layer transfer sheet held in a releasable state on a carrier copper foil, transferring and attaching the transferred copper foil to at least one surface of an insulating base material via a prepreg to form a copper base layer Forming a mask on the copper underlayer, forming a copper plating layer at a location exposed from the opening of the mask, and etching after removing the mask, A gist of the present invention is a method for manufacturing a printed wiring board, which comprises a conductor pattern cutting step of cutting a conductor pattern by removing a copper base layer.

According to a second aspect of the present invention, in the method for manufacturing a printed wiring board having plated through holes and conductive patterns, the transferred copper foil is held in a releasable state on a carrier copper foil thicker than the transferred copper foil. Using a conductive layer transfer sheet, and transferring and attaching the transferred copper foil to both sides of the insulating base material through a prepreg, thereby forming a copper base layer, and passing through a predetermined portion of the insulating base material. A hole forming step for forming a hole for forming a hole, a first plating step for forming a thin copper plating layer on the inner wall surface of the copper base layer and the through hole forming hole, and a mask on the thin copper plating layer. And a second plating step of forming a thick copper plating layer in a portion exposed from the opening of the mask, and etching after removing the mask to form the same mask. A method of manufacturing a printed wiring board, comprising: performing a conductor pattern dividing step of separating the conductor patterns by removing the thinned copper plating layer and the copper base layer under the metal layer.

According to a third aspect of the present invention, in the first or second aspect, the conductor pattern dividing step by the etching is performed without providing an etching resist on the copper plating layer located at the outermost layer. did.

[0011] The invention according to claim 4 is the invention according to claims 1 to 3.
In any one of the above, the thickness of the transfer copper foil is 10μ
m, and the thickness of the carrier copper foil is 10 μm to 5 μm.
It was assumed to be 0 μm.

[0012] The invention according to claim 5 provides the invention according to claims 1 to 4.
In any one of the above, in the conductor pattern dividing step, an annealing step is performed after the mask is removed and before the etching is performed.

According to a sixth aspect of the present invention, in the printed wiring board provided with a conductor pattern, the conductor pattern is formed on a copper base layer having a thickness of less than 10 μm provided on an insulating base material and on the copper base layer. First thickness of 3 μm or less
It is composed of a copper plating layer and a second copper plating layer having a thickness of 5 μm to 50 μm formed on the first copper plating layer, and a length of a side far from the insulating base material in a cross section of the conductor pattern is The length of the side closer to the insulating base is 0.9 to
The gist of the present invention is a printed wiring board characterized by 1.2.

The "action" of the present invention will be described below. According to the invention as set forth in claim 1, the transfer copper foil is peeled off from the carrier copper foil and transferred and adhered, so that a thin copper base layer derived from the transfer copper foil of the conductor layer transfer sheet is placed on the insulating base material. Is formed. Then, by forming the copper plating layer in a state where the mask is formed, only a portion to be a conductor pattern later becomes selectively thick. Thereafter, etching is performed to remove the copper underlayer under the mask, so that the conductor patterns are separated from each other. Since the copper underlayer of the present invention is relatively thin, the thickness to be removed by etching in the conductor pattern cutting step is considerably small. Therefore, the divided and formed conductor pattern is unlikely to have a flared shape, and a fine pattern having a good shape can be accurately formed.

The transferred copper foil is held by a thicker carrier copper foil. Therefore, even if the transfer copper foil itself is extremely thin, it will have a certain thickness when viewed as the entire conductor layer transfer sheet, and suitable rigidity will be imparted to the entire conductor layer transfer sheet. For this reason, deformation and damage of the transferred copper foil are avoided, and handling properties are improved.

According to the second aspect of the present invention, the transfer copper foil is peeled off from the carrier copper foil and transferred and adhered, so that a thin layer derived from the transfer copper foil of the conductor layer transfer sheet is formed on the insulating base material. A copper underlayer is formed. Then, by forming the thick copper plating layer in a state where the mask is formed, only the portion which is to become a conductor pattern later becomes selectively thick. Thereafter, etching is performed to remove the thin copper plating layer and the copper base layer under the mask, whereby the conductor patterns are separated from each other. Since the copper underlayer of the present invention is relatively thin, the thickness to be removed by etching in the conductor pattern cutting step is considerably small. Therefore, the divided and formed conductor pattern is unlikely to have a flared shape, and a fine pattern having a good shape can be accurately formed.

Further, the transfer copper foil is held by a thicker carrier copper foil. Therefore, even if the transfer copper foil itself is extremely thin, it will have a certain thickness when viewed as the entire conductor layer transfer sheet, and suitable rigidity will be imparted to the entire conductor layer transfer sheet. For this reason, deformation and damage of the transferred copper foil are avoided, and handling properties are improved.

According to the third aspect of the present invention, in the conductor pattern dividing step, the step of forming and peeling the etching resist is not required, so that the number of steps is reduced and the productivity is improved. Further, the thickness by which the copper plating layer is removed by the etching at this time is extremely small, and does not particularly adversely affect the pattern formation accuracy and the like.

According to the fourth aspect of the present invention, by setting the thicknesses of the transfer copper foil and the carrier copper foil within the above preferred ranges, it is possible to reliably avoid the deformation and damage of the transfer copper foil. In addition, it is possible to reliably prevent a decrease in productivity and an increase in cost.

When the thickness of the transfer copper foil is 10 μm or more,
A sufficiently thin copper base layer cannot be formed, and the thickness to be removed by etching in the conductor pattern cutting step cannot be sufficiently reduced. Further, when the thickness of the carrier copper foil is less than 10 μm, it is not possible to impart suitable rigidity to the entire conductor layer transfer sheet, and it is difficult to reliably avoid deformation and damage of the transfer copper foil. . If the thickness of the carrier copper foil exceeds 50 μm, the rigidity becomes too strong, and the peeling operation becomes rather difficult, which may lead to a decrease in productivity. In addition, the cost is increased by using a large amount of copper.

According to the fifth aspect of the present invention, the stress existing in the copper plating layer is released by heating by performing the annealing step after the mask is removed and before the etching is performed. As a result, pinholes are less likely to occur in the copper plating layer, and a highly reliable conductor pattern can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a printed wiring board 1 according to an embodiment of the present invention and a method for manufacturing the same will be described with reference to FIGS.
This will be described in detail based on FIG.

As shown in FIG. 9, the printed wiring board 1 of the present embodiment has conductor patterns 2 a and 2 b formed by a subtractive method and plated through holes 3 on the front and back of an insulating base material 4. This multilayer printed wiring board 1 is a so-called four-layer board having four conductor layers. As the insulating substrate 4, for example, a glass cloth substrate impregnated with an epoxy resin, a polyimide resin, a BT (bismaleimide triazine) resin, or the like is used. In the present embodiment, a substrate (so-called glass epoxy substrate) impregnated with a relatively inexpensive epoxy resin is selected.

An inner conductor pattern 2a is formed on both front and back surfaces of the insulating base material 4. The inner layer conductor pattern 2a is obtained by, for example, etching a copper foil provided on the insulating base material 4. Outer conductor patterns 2b are formed on the inner conductor patterns 2a on both front and back sides with prepregs 34 interposed therebetween.

As shown in FIG. 1, the outer conductor pattern 2b includes a copper base layer 6, a thin copper plating layer 7 as a first copper plating layer, and a thick copper plating layer as a second copper plating layer. 8 That is, the outer conductor pattern 2b is 3
It has a layer structure. The thin copper plating layer 7 is formed on the copper base layer 6, and the thick copper plating layer 8 is formed on the thin copper plating layer 7.

The possible range of the thickness of the copper underlayer 6 is 10 μm.
m, and particularly preferably 1 μm to 5 μm. The possible range of the thickness of the thin copper plating layer 7 is 3 μm.
Or less, and particularly preferably from 0.5 μm to 2 μm. The possible range of the thickness of the thick copper plating layer 8 is 5 μm.
To 50 μm, and particularly preferably 10 μm to 25 μm. In the present embodiment, specifically, the copper base layer 6
3 μm, and the thickness of the thin copper plating layer 7 is 1.5 μm.
m, and the thickness of the thick copper plating layer 8 is set to 20 μm.

Here, in the cross section of the outer layer conductor pattern 2b, the length of the side farther from the insulating base material 4 (that is, the length of the top portion) is defined as L1, and the length of the side closer to the insulating base material 4 is defined as L1. The length (that is, the length of the bottom portion) is defined as L2. In this case, the value of L1 / L2 is 0.9 to 1.2, which is a shape that cannot be said to be a so-called skirt spread. In addition,
In the present embodiment, the space between adjacent outer layer conductor patterns 2b is set to about 35 μm,
Is set to about 70 μm.

The conductor patterns 2 a and 2 b of each layer are electrically connected to each other through a plated through hole 3 formed so as to penetrate the insulating base material 4. The conductor layer in the plated through hole 3 is composed of a thin copper plating layer 7 formed on the inner wall surface of the through hole forming hole 10 and a thick copper plating layer 8 formed on the thin copper plating layer 7. Become. That is, the conductor layer in the plating through hole 3 has a two-layer structure. The land 3a of the plated through hole 3 has the same structure as the outer conductor pattern 2b, that is, has a three-layer structure.

Next, the multilayer printed wiring board 1 of the present embodiment
Will be described. First, prior to this, the conductor layer transfer sheet 31 used in the present embodiment will be described. As shown in FIG. 2, the conductor layer transfer sheet 31
Is roughly constituted by a transfer copper foil 32 and a carrier copper foil 33.

The transfer copper foil 32 is held on one side of the carrier copper foil 33 in a releasable state. Specifically,
For example, the transfer copper foil 32 is attached to one side of the carrier copper foil 33 using an adhesive or a pressure-sensitive adhesive having a not so large bonding force. The reason for this is that if the bonding force is too large, the transfer copper foil 32 is difficult to peel off, leading to deformation and the like. Of course, the transfer copper foil 32 may be stuck and held on the carrier copper foil 33 without using an adhesive or the like.

The carrier copper foil 33 is thicker than the transfer copper foil 32. Specifically, the thickness of the transfer copper foil 32 is preferably less than 10 μm, and more preferably 1 μm to 5 μm. The thickness of the carrier copper foil 33 is 10 μm or more.
It is preferably 50 μm, more preferably 30 μm to 40 μm.

If the thickness of the transfer copper foil 32 is 10 μm or more, a sufficiently thin copper base layer 6 cannot be formed, and the thickness to be removed by etching in the conductor pattern cutting step can be sufficiently reduced. Disappears. Further, if the thickness of the carrier copper foil 33 is less than 10 μm, it is not possible to impart a suitable rigidity to the entire conductor layer transfer sheet 31, and it is possible to reliably avoid the transfer copper foil 32 from being deformed or damaged. It becomes difficult. In addition, as a result of the carrier copper foil 33 itself being easily deformed, there is a possibility that it cannot be reused. When the thickness of the carrier copper foil 33 exceeds 50 μm, the rigidity becomes too strong, and as a result, the peeling work becomes difficult,
This may lead to a decrease in productivity. In addition, the cost is increased by using a large amount of copper. In the present embodiment, in consideration of the above circumstances, the transfer copper foil 32 is set to have a thickness of 3 μm, and the carrier copper foil 33 is set to have a thickness of 35 μm, which is a common thickness. The reason why the copper foil was selected as the carrier foil is that copper is inexpensive and excellent in economic efficiency. The reason why copper foil was selected as the transfer foil is that copper is not only inexpensive and economical, but also excellent in etching properties.

Then, the copper-clad laminate 5 is used as a starting material, and the inner conductor patterns 2a are formed on both front and back surfaces of the insulating base material 4 constituting the same. Then, the conductor layer transfer sheet 31 is laminated on both front and back surfaces of the insulating base material 4 via a prepreg 34. At this time, the transfer copper foil 32 is directed to the inner layer side. Then, a heat press is performed by a laminating apparatus, and the transferred copper foil 32 is transferred and adhered to the insulating base material 4 via the prepreg 34. As shown in FIG. 6 is formed.

Thereafter, the carrier copper foil 33 is turned up and peeled off from the transfer copper foil 32, thereby removing the carrier copper foil 33 and exposing the transfer copper foil 32. The rolled-up carrier copper foil 33 is recovered, and a new transfer copper foil 32 is recovered.
May be used again as the conductor layer transfer sheet 31.

In the subsequent drilling step, a through hole forming hole 10 having a diameter of 0.1 mm to 0.2 mm is formed in a predetermined portion of the insulating base material 4 having undergone the copper base layer forming step by drilling (see FIG. 4). . If it is desired to form a smaller diameter through hole forming hole 10, laser processing may be performed instead of drilling.

When such a drilling step is performed, smear may occur in the through-hole forming hole 10 due to heat generation. In such a case, the copper-clad laminate 5 may be treated with a desmear liquid in order to dissolve and remove the generated smear. Note that desmear treatment can be performed by a plasma method. In the desmear process, under the condition that the ultra-thin transfer copper foil 32 does not disappear, specifically, the transfer copper foil 3
It is preferable to treat the desmear liquid under the condition that the thickness of No. 2 is reduced to 1/10 to 1/2 of the initial thickness. In this case, a solution of sulfuric acid, chromic acid, alkali permanganate, or the like is used as the desmear liquid.

After performing the desmearing step as required, a catalyst nucleus for depositing plating on the inner wall surface of the through-hole forming hole 10 is then provided, and the catalyst nucleus is activated. A noble metal ion or a noble metal colloid is used for providing the catalyst nucleus, and generally, palladium chloride or a palladium colloid is used.

After the catalyst nucleus is applied and activated, a thin copper plating layer 7 is formed by electroless copper plating on the entire surface of the copper base layer 6 and on the inner wall surface of the through hole forming hole 10. (See FIG. 5).

In the first plating step, an electroless copper plating bath, which is a kind of an electroless plating bath, is used, and the thickness is 3 μm or less, preferably 0.5 μm to 2 μm.
A μm thin copper plating layer 7 is formed. If the thin copper plating layer 7 is too thin, it may not be possible to reliably deposit electrolytic copper plating on the entire inner wall surface of the through-hole forming hole 10 in a later plating step. Therefore,
This may lead to poor conduction of the plated through hole 3 and may not be able to sufficiently improve the reliability. Conversely, if the thinned copper plating layer 7 is formed too thick, the productivity is reduced and the cost is increased, and the thickness to be removed by etching in the conductor pattern cutting step cannot be sufficiently reduced. There is a risk.

After the first plating step, a predetermined mask 11 serving as a plating resist is formed on the thin copper plating layer 7. In this case, the mask 11 is preferably formed using a commercially available dry film photoresist. This is because the use of a photosensitive material contributes to an improvement in pattern formation accuracy. Then, after laminating such a dry film photoresist, exposure and development are performed according to a conventional method. As a result, as shown in FIG. 6, a mask 11 having a thickness of 35 μm and having openings 12 at predetermined locations is formed.

After the mask forming step, a thick copper plating layer 8 is formed in a portion exposed from the opening 12 using an electrolytic copper plating bath, which is a type of electrolytic plating (see FIG. 7). When such a thick copper plating layer 8 is formed, only the portion to be the outer conductor pattern 2b later becomes selectively thick. In this embodiment, a copper sulfate plating bath is used as the electrolytic copper plating bath. As a result of the second plating, a thickness of 5 μm is formed on the thin copper plating layer 7 located at the exposed portion.
A thick copper plating layer 8 having a thickness of about m to 50 μm is formed.
If the thick copper plating layer 8 is too thin, it is not possible to sufficiently secure the thickness of the finally obtained outer conductor pattern 2b. Conversely, if the thick copper plating layer 8 is too thick, productivity may be reduced and costs may be increased.

After the second plating step, the unnecessary mask 11 is peeled off, exposing the thin copper plating layer 7 located thereunder (see FIG. 8). At this point, it is desirable to perform an annealing step at a predetermined temperature and a predetermined temperature. The reason for this is that the heating at the time of annealing releases the stress inherent in the thick copper plating layer 8, and the thick copper plating layer 8 is in a state of being baked. As a result, pinholes are less likely to occur in the thick copper plating layer 8, and a highly reliable outer conductor pattern 2b can be obtained. The annealing temperature is 100 ° C.
The temperature is preferably set to about 200 ° C., and is set to 150 ° C. in the present embodiment. Annealing time is 0.
It is often set to about 1 hour to 3 hours, and in this embodiment, it is set to 1 hour.

Next, an etching treatment is performed using a sulfuric acid / hydrogen peroxide solution capable of dissolving copper to completely remove the thin copper plating layer 7 and the copper base layer 6. Here, since the processing is performed without providing an etching resist on the thickest copper plating layer 8 located at the outermost layer, the surface layer of the thick copper plating layer 8 is also etched by about 2 to 3 μm. Then, through the above steps, the outer conductor patterns 2b are separated from each other, and the multilayer printed wiring board 1 shown in FIG.
Was completed.

Therefore, according to the present embodiment, the following effects can be obtained. (1) In the manufacturing method of the present embodiment, the conductor layer transfer sheet 31 having the above configuration is used. Therefore, the transfer copper foil 32 is peeled off from the carrier copper foil 33 and transferred and adhered, so that an extremely thin copper base layer 6 derived from the transfer copper foil 32 can be formed on the insulating base material 4. By forming the thick copper plating layer 8 in a state where the mask 11 is formed, only the portion which is to become the outer conductor pattern 2b later becomes selectively thick. Thereafter, the outer conductor patterns 2b are separated from each other by performing etching to remove the thin copper plating layer 7 and the copper base layer 6 that were under the mask 11.

Since the copper underlayer 6 of this embodiment is extremely thin, the thickness to be removed by etching in the conductor pattern dividing step is considerably small, 2 μm to 3 μm. Therefore, the divided outer conductor pattern 2b is unlikely to have a flared shape, and a fine pattern having a good shape as shown in FIG. 1 can be accurately formed.

(2) The transferred copper foil 32 is held by a thicker carrier copper foil 33. Therefore, even if the transfer copper foil 32 itself is extremely thin, the conductor layer transfer sheet 31 as a whole has a thickness of 35 μm or more, and a suitable rigidity is provided. For this reason, the transfer copper foil 32 is prevented from being deformed or damaged, and the handling property is improved. That is, it is not necessary to handle the transfer copper foil 32 as carefully as when it is used alone. Therefore, there is no decrease in productivity due to difficult handling. In addition, as a result of preventing the transfer copper foil 32 from being deformed or damaged, it is possible to improve the yield of the multilayer printed wiring board 1 and achieve high reliability.

(3) The carrier copper foil 33 of the present embodiment can be recycled by collecting it after peeling and holding a new transfer copper foil 32. For this reason,
It is very economical and contributes to a reduction in the manufacturing cost of the multilayer printed wiring board 1.

(4) Carrier copper foil 33 and transfer copper foil 32
Are made of the same material and have the same coefficient of thermal expansion. Therefore, the transferred copper foil 32 does not warp, wrinkle, peel, or the like even after the heating press, which is advantageous in achieving high accuracy and high reliability of the outer layer conductor pattern 2b.

(5) Since the carrier copper foil 33 is made of copper having excellent thermal conductivity, the carrier copper foil 33 does not have a thermal resistance at the time of hot pressing, and can surely transmit heat to the transfer copper foil 32 side. Therefore, the transfer copper foil 32 can be securely adhered to the prepreg 34. This also contributes to improved reliability.

(6) In the present embodiment, by using an electroless copper plating bath in the first plating step and using an electrolytic copper plating bath in the second plating step, the conductor in the multilayer printed wiring board 1 is Forming a layer. In other words,
An electroless copper plating bath is used only when depositing plating on the inner wall surface of the through-hole forming hole 10, and thereafter, an extremely inexpensive electrolytic copper plating bath having a high plating deposition rate is used. For this reason, cost and productivity can be further improved.

(7) This multilayer printed wiring board 1 has a copper underlayer 6 having a thickness of less than 10 μm, a thin copper plating layer 7 having a thickness of 3 μm or less formed thereon, and a copper plating layer 7 having a thickness of 3 μm or less. A conductive pattern 2b having a three-layer structure including a thick copper plating layer 8 having a thickness of 5 μm to 50 μm is provided. The metals forming these three layers are of the same type (ie, copper). Further, L1 / L2 in the conductor pattern 2b
Is 0.9 to 1.2. In such a conductor pattern 2b, a sufficient thickness and conductivity as a conductive portion, a suitable sectional shape, and the like are secured. Therefore, the multilayer printed wiring board 1 is excellent in reliability, cost performance, and pattern formation accuracy, and has high performance and high density.

The embodiment of the present invention may be modified as follows. -The present invention is not limited to being embodied in a four-layer board as in the embodiment, and may be embodied in a multilayer printed wiring board. For example, the multilayer printed wiring board 1 of the embodiment may be used as a core substrate or a base substrate, and the outer conductor pattern 2b may be further formed on one surface or both surfaces of the substrate using the conductor layer transfer sheet 31. In other words, a plurality of outer conductor patterns 2b having the copper base layer 6 derived from the conductor layer transfer sheet 31 may exist on the same side surface of the insulating base material 4. In addition,
Instead of forming the outer conductor pattern 2b using the conductor layer transfer sheet 31, it is also possible to form a build-up layer by a conventionally known method.

Instead of the wet method as described in the embodiment, a desmear process by a dry method typified by, for example, a plasma method may be performed. Of course, the desmear step may be omitted unless it is particularly necessary.

The plated through hole 3 is not an essential component and may be omitted. When the plated through hole 3 is not formed, the plated through hole 3
The first plating step for establishing electrical continuity is also omitted.

The transfer copper foil 32 may be transferred and adhered to both sides of the insulating base material 4 or may be transferred and adhered to only one side. In other words, the copper base layer 6 may be formed on both surfaces of the insulating base material 4 or may be formed on only one surface.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments will be listed below together with their effects. (1) A conductive layer transfer sheet in which a transfer copper foil is detachably held on a carrier copper foil thicker than the transfer copper foil, and the transfer copper foil is applied to at least one surface of an insulating base material via a prepreg. A method for reusing a carrier copper foil, wherein a new conductive copper foil is again held on the carrier copper foil after the transfer / sticking to prepare a new conductive layer transfer sheet. Therefore, according to the invention described in the technical idea 1,
It is economical because the carrier copper foil can be recycled.

(2) In a method for manufacturing a multilayer printed wiring board having a plurality of conductor patterns, a step of forming an inner conductor pattern on an insulating base material and a step of forming a transfer copper foil thicker than the transfer copper foil Using a conductive layer transfer sheet held in a releasable state on the upper side, forming a copper base layer by transferring and attaching the transferred copper foil to the inner layer conductive pattern forming surface of the insulating base material via a prepreg And forming a mask on the copper underlayer, forming a copper plating layer at a location exposed from the opening of the mask, and etching after removing the mask, And a conductor pattern dividing step of dividing the outer conductor pattern by removing the copper base layer.

[0058]

As described in detail above, according to the first to fifth aspects of the present invention, a printed wiring capable of forming a fine conductor pattern having a good shape without a decrease in productivity. A method for manufacturing a plate can be provided.

According to the invention described in claim 6, reliability,
A printed wiring board excellent in cost performance and pattern formation accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of an outer layer conductor pattern in a multilayer printed wiring board according to an embodiment of the present invention.

FIG. 2 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board according to the embodiment.

FIG. 3 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 4 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 5 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 6 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 7 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 8 is a partial schematic cross-sectional view for explaining a manufacturing procedure of the multilayer printed wiring board.

FIG. 9 is a partial schematic cross-sectional view of the multilayer printed wiring board.

FIG. 10 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.

FIG. 11 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.

FIG. 12 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.

FIG. 13 is a partial schematic cross-sectional view for explaining a manufacturing procedure of a conventional multilayer printed wiring board.

FIG. 14 is a partial schematic cross-sectional view of a conventional multilayer printed wiring board.

[Explanation of symbols]

1. Multilayer printed wiring board as printed wiring board, 2a
... (inner layer) conductor pattern, 2b ... (outer layer) conductor pattern, 3 ... plated through hole, 4 ... insulating base material, 6 ... copper base layer, 7 ... thin copper plating layer as first copper plating layer,
8 ... thick copper plating layer as second copper plating layer, 10 ...
Holes for forming through holes, 11: mask, 12: opening of mask, 31: conductive layer transfer sheet, 32: transfer copper foil, 3
3: carrier copper foil, 34: prepreg, L1: length of side far from insulating base material, L2: length of side near insulating base material.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (6)

[Claims] 1. A method for manufacturing a printed wiring board having a conductor pattern, comprising: using a conductor layer transfer sheet in which a transfer copper foil is detachably held on a carrier copper foil thicker than the transfer copper foil; A step of forming a copper underlayer by transferring and attaching a copper foil to at least one surface of an insulating base material via a prepreg, and forming a mask on the copper underlayer, and exposing the mask from an opening of the mask. Performing a step of forming a copper plating layer in a portion where the copper base layer is formed, and performing a conductor pattern dividing step of removing the copper base layer and dividing the conductor patterns by etching after removing the mask. A method for manufacturing a printed wiring board, which is a feature. 2. A method for manufacturing a printed wiring board having a plated through hole and a conductor pattern, comprising: a conductor layer transfer sheet holding a transfer copper foil in a releasable state on a carrier copper foil thicker than the transfer copper foil; A step of forming a copper base layer by transferring and attaching the transferred copper foil to both sides of the insulating base material via a prepreg, and forming a through-hole forming hole at a predetermined position of the insulating base material. Drilling step, a first plating step of forming a thin copper plating layer on the inner wall surface of the copper base layer and the through-hole forming hole, and forming a mask on the thin copper plating layer,
A second plating step of forming a thick copper plating layer at a position exposed from an opening of the mask, and etching after removing the mask to form the thinned copper under the mask. A method of separating a conductive pattern by removing a plating layer and the copper base layer to separate conductive patterns from each other. 3. The printed wiring according to claim 1, wherein the step of dividing the conductor pattern by etching is performed without providing an etching resist on the outermost copper plating layer. Plate manufacturing method. 4. The print according to claim 1, wherein said transfer copper foil has a thickness of less than 10 μm, and said carrier copper foil has a thickness of 10 μm to 50 μm. Manufacturing method of wiring board. 5. The printed wiring according to claim 1, wherein an annealing step is performed between the time when the mask is peeled and the time when the etching is performed in the conductive pattern dividing step. Plate manufacturing method. 6. A printed wiring board provided with a conductor pattern, wherein the conductor pattern comprises a copper base layer provided on an insulating base material and having a thickness of less than 10 μm, and a copper base layer having a thickness of 3 μm or less formed on the copper base layer. A first copper plating layer, a second copper plating layer having a thickness of 5 μm to 50 μm formed on the first copper plating layer, and a length of a side farther from the insulating base in a cross section of the conductor pattern; The length of the side near the insulating base is 0.9 to 1.2.