JP4161604B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printed wiring board for mounting electronic components such as surface mount components, particularly bare chips, and a method for manufacturing the same.
[0002]
[Prior art]
Due to recent demands for higher functionality, smaller size, and lighter electronic devices such as information terminals and communication terminals, high integration and high speed technologies for semiconductors are rapidly progressing.
[0003]
Therefore, high-density wiring and high-density mounting are possible for printed wiring boards on which electronic parts such as bare chips for achieving miniaturization and light weight are achieved, and inexpensive ones are required.
[0004]
In order to meet such market demands, instead of the conventional printed wiring board based on copper-plated through-hole connection, interstitial via holes (hereinafter referred to as IVH) are filled with conductive paste. A multilayer printed wiring board (Japanese Patent Laid-Open No. 6-268345) having an all-layer IVH structure that can be manufactured at low cost by forming IVH directly under a component land or between arbitrary layers is developed and supplied to the market. Yes.
[0005]
This multilayer printed wiring board having an all-layer IVH structure has a through-hole formed in a base material, and after filling the through-hole with a conductive paste, the metal foil is laminated and heated and pressed to establish an interlayer connection. Is.
[0006]
A conventional method for manufacturing a printed wiring board will be described below.
[0007]
FIG. 5 is a process sectional view showing a conventional method of manufacturing a printed wiring board.
[0008]
First, a base 22 having a release film 21 such as polyester on both sides is prepared. As this base material, for example, a base material obtained by impregnating a non-woven fabric of resin fiber or glass fiber with a thermosetting epoxy resin is used (FIG. 5A).
[0009]
Next, a through hole 23 is formed at a predetermined location of the base material 22 (FIG. 5B), and the conductive paste 24 is filled. As a filling method, the conductive paste 24 is printed directly on the release film 21 (FIG. 5C).
[0010]
Next, after peeling off the release film 21 from both surfaces of the base material 22, a metal foil such as copper foil 25 is pasted on both surfaces (FIG. 5D), and heated and pressurized with a vacuum hot press machine, The base material 22 is compressed and bonded to the copper foil 25 (FIG. 5E).
[0011]
In this process, the conductive paste is also compressed. At that time, the binder component is extruded from between the conductive materials, and the bonds between the conductive materials and between the conductive material and the copper foil are strengthened. As the material is densified, the base material is also compressed, and the epoxy resin and the conductive paste 24 which are constituent parts of the base material 22 are cured. As a result, the connection resistance value is low and the interlayer is highly reliable. A connection is obtained.
[0012]
Thereafter, the copper foil 25 is selectively etched by a photo process to form a predetermined wiring pattern 26 (FIG. 5F).
[0013]
At present, the density of the land has been further reduced as the density of wiring of the substrate has further increased, and accordingly, the diameter of the through hole serving as a via hole has been required to be reduced.
[0014]
However, in the configuration and the manufacturing method as described above, when the diameter of the through hole is reduced, the initial connection resistance value increases and the variation also increases.
[0015]
Further, reliability tests such as a temperature cycle test and a pressure cooker test (destructive test under high temperature and high pressure) have a problem that the connection resistance value fluctuates. This is because when the diameter of the through hole is reduced, the filling property of the conductive paste is deteriorated, and the compression rate necessary for stabilizing the electrical connection cannot be secured.
[0016]
Also, in the process of peeling the release film, if the through-hole diameter is small, the conductive paste is easily attached to the release film side when peeling the release film, and it is taken into the through-hole. The filling amount of the conductive paste is reduced. As a result, compression of the conductive paste necessary for stabilizing the electrical connection cannot be ensured.
[0017]
Therefore, a printed wiring board by a transfer method and a method for manufacturing the same have been devised as a method of compensating for the decrease in compression.
[0018]
6 and 7 are process sectional views showing a method for manufacturing a printed wiring board by a conventional transfer method.
[0019]
First, a transfer plate 30 comprising a copper foil 32 as a metal foil and a support substrate 31 is prepared (FIG. 6A).
[0020]
Next, a wiring pattern for transfer using a photo process is formed on the support substrate on which the copper foil is formed.
[0021]
After forming an etching resist 33 on the surface of the copper foil 32 formed on the support substrate 31 by a photo process (FIG. 6B), unnecessary copper foil is removed with an etching solution such as cupric chloride. After the predetermined wiring pattern 34 is formed (FIG. 6C), the etching resist 33 is peeled off to complete the pattern formation, thereby completing the production of the first transfer plate 30 (FIG. 6D). ).
[0022]
Next, a second transfer plate 41 in which different wiring patterns 36 are formed on the support substrate 35 is manufactured by a transfer plate manufacturing method similar to the above (FIG. 6E).
[0023]
Next, a base material 38 having a release film 37 such as polyester on both sides is prepared (FIG. 7F).
[0024]
Next, a through hole 39 is formed at a predetermined position of the base material 38 (FIG. 7G), and the conductive paste 40 is filled. As a filling method, the conductive paste 40 is printed directly on the release film 37.
[0025]
Next, after the release film 37 is peeled from both surfaces of the base material 38 (FIG. 7H), the first transfer plate 30 and the second transfer plate 41 prepared above are opposed to each other, and the conductive film is conductive between them. The base material 38 filled with the paste 40 is superposed (FIG. 7 (I)), and the base material 38 is compressed by heating and pressing from both sides of the first and second transfer plates with a vacuum hot press. At the same time, the wiring patterns 34 and 36 are embedded in the substrate 38 and bonded to the conductive paste 40 in the through hole 39 (FIG. 7J).
[0026]
Next, by removing the support substrates 31 and 35 chemically or mechanically, a wiring substrate having the wiring patterns 34 and 36 embedded in the base material 38 is obtained (FIG. 7K).
[0027]
In this way, in addition to compressing the conductive paste together with the base material, the conductive paste is further compressed by embedding the wiring pattern, and the conductive material in the conductive paste is densified, so the connection resistance value is reduced. Low and reliable interlayer connection can be obtained.
[0028]
[Problems to be solved by the invention]
The conventional printed wiring board has the following problems. In the background where thinning has progressed and high precision of wiring pattern formation is required, it has become necessary to reduce the thickness of the copper foil 25 in order to realize this, but if the thickness of the copper foil 25 is reduced Although it is easy to cope with thinning, since the wiring pattern 26 is thin, the depth (thickness) of the wiring pattern 26 embedded in the base material is reduced. For this reason, the compressibility of the conductive paste 24 is reduced, so that the initial connection resistance value is increased. As a result, there is a problem that the variation in the initial connection resistance value is increased.
[0029]
Accordingly, the present invention solves the above-described conventional problems, and the conductive paste can be sufficiently compressed even when the via hole diameter is reduced and the wiring pattern is refined, so that the connection resistance value is low and the printing is highly reliable. An object of the present invention is to provide a wiring board and a manufacturing method thereof.
[0030]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 of the present invention is A circuit having a metal layer having a rectangular cross section at the top is embedded from both sides of the interlayer adhesive sheet so that the metal layers face each other, and the metal layer embedded from both sides of the interlayer adhesive sheet is electrically connected. The conductive hole is formed by compressing the conductive paste filled in the through hole of the interlayer adhesive sheet from both sides by the circuit having the metal layer on the upper side. And the width of the metal layer is larger than the width of the circuit at the contact surface between the circuit and the metal layer. As a result, sufficient compression is applied to the conductive paste filled in the through holes provided at predetermined positions of the base material, and the conductive material in the conductive paste is densified, so that the connection resistance value is A printed wiring board having a low and highly reliable interlayer connection can be realized.
[0031]
The invention according to claim 2 of the present invention is the printed wiring board according to claim 1, in particular, wherein the metal layer is formed by electrolytic plating, whereby the compressibility of the conductive paste. The effect that the thickness of the metal layer for controlling the thickness can be easily set is obtained.
[0032]
The invention according to claim 3 of the present invention is the printed wiring board according to claim 1, characterized in that, in particular, the constant thickness of the metal layer is 5 to 10% of the thickness of the interlayer adhesive sheet. As a result, even if the thickness of the wiring pattern is reduced due to thinning, a metal layer with a certain thickness is embedded inside the base material, so that the conductive paste is sufficiently compressed, and the connection resistance value is reduced. A printed wiring board having a low and highly reliable interlayer connection can be obtained.
[0033]
Also book The invention is particularly characterized in that the interlayer adhesive sheet is provided with a conduction hole. The This is a lint wiring board, and when it is multi-layered, only necessary layers can be conducted between any layers, so there is no dead space (unnecessary space) generated due to conduction between unnecessary layers. Can be realized.
[0034]
Also book The invention is particularly characterized in that the conduction hole is formed by filling a conductive paste. The Since it is a lint wiring board, it is not necessary to consider throwing power (circularity with plating) as compared with the conventional plating conduction hole, so that an effect that the diameter can be significantly reduced is obtained.
[0035]
Also book In particular, the invention is characterized in that the metal layer formed on the first transfer plate and the metal layer formed on the second transfer plate are electrically connected through a conduction hole. The This is a lint wiring board, so that only necessary layers can be connected between any layers, so that dead space does not occur and high density can be realized, and even if the amount of conductive paste filling decreases as the diameter decreases Since the conductive paste is sufficiently compressed while the circuit formed on the support substrate and the metal layer formed on the circuit are embedded in the interlayer adhesive sheet, a printed wiring board having a low connection resistance value can be realized. .
[0036]
Claims of the invention 4 In particular, the invention described in item 1 is characterized in that the interlayer adhesive sheet is an aramid nonwoven fabric epoxy resin impregnated sheet. The Since the specific gravity of the aramid nonwoven fabric epoxy resin impregnated sheet is smaller than that of the conventional glass nonwoven fabric epoxy resin impregnated sheet, the substrate becomes light and effective in reducing the weight of the product.
[0037]
Claims of the invention 5 In particular, the metal layer is characterized in that the size of the metal layer is 40 to 150 μm larger than the conduction hole. The When a positional deviation occurs when a conventional transfer board and an interlayer adhesive sheet having conductive holes filled with a conductive paste are overlapped, the positional deviation tolerance is limited to a certain range. Therefore, the conductive paste is exposed to the surface of the interlayer adhesive sheet, flows out, and an effect of eliminating the problem that causes the short circuit is obtained.
[0038]
Claims of the invention 6 In particular, the invention described in item 1 is characterized in that the interlayer adhesive sheet is a porous material having compressibility. The Since it is a lint wiring board, and the conductive paste is also compressed at the same time as the interlayer adhesive sheet is compressed, the binder component in the conductive paste is extruded toward the interlayer adhesive sheet which is a porous material, Since the bonding between the conductive materials and between the conductive material and the copper foil is strengthened and the conductive material in the conductive paste is densified, the connection resistance value is low and a highly reliable interlayer connection can be obtained.
[0039]
Claims of the invention 7 In particular, the invention described in 1 is characterized in that the compressibility of the porous material having compressibility is 10 to 50%. The This is a lint wiring board, which makes it easier for the circuit and the metal layer to be embedded in the porous material when the porous material is compressed. The conductive material in the conductive paste is further densified by the interaction between the thickness of the embedded circuit and the thickness of the metal layer, so that the connection resistance value is low and a reliable interlayer connection can be obtained. it can.
[0040]
Claims of the invention 8 In particular, the invention described in item 1 is characterized in that the resin content of the sheet for interlayer adhesion is 40 to 65%. The This is a lint wiring board, and when the porous material is compressed, the resin wraps around the circuit and the metal layer, so that a printed wiring board having no voids and excellent flatness can be obtained.
[0041]
Claims of the invention 9 In particular, the invention described in (1), a step of preparing the first and second transfer plate in which the metal foil is formed on the support substrate; Above On the metal foil of the first and second transfer plates Rectangular cross section A step of selectively forming a metal layer having a metal layer, and using the metal layer as an etching resist. Etching the metal foil until the width of the metal foil at the contact surface between the metal layer and the metal foil is smaller than the width of the metal layer. A step of forming a circuit, a step of preparing a sheet for interlayer adhesion, Above The circuit forming surfaces of the first and second transfer plates Above Interlayer adhesion for A step of facing and stacking through the sheet Addition Heat and pressure process And the step of preparing the interlayer adhesive sheet includes a step of forming a through hole in the interlayer adhesive sheet and a step of filling the through hole with a conductive paste. The printed wiring board manufacturing method is characterized in that the conductive paste filled in the through holes provided at predetermined positions of the base material is sufficiently compressed, and the conductive substance in the conductive paste Therefore, a printed wiring board having a low connection resistance value and a highly reliable interlayer connection can be realized.
[0042]
Claims of the invention 10 In the invention described in (2), the step of selectively forming the metal layer is characterized in that a plating resist is formed by a photo process, and an electrolytic nickel plating layer is formed in a portion where the plating resist is not formed. The In this method, the thickness of the metal layer for controlling the compressibility of the conductive paste can be easily set. Moreover, since the electrolytic nickel plating layer has high hardness, the effect that it can be easily embedded in the interlayer adhesive sheet by heating and pressing can be obtained.
[0043]
Claims of the invention 11 In particular, the thickness of the metal layer is set to 5 to 10% of the thickness of the interlayer adhesive sheet using an electrolytic plating process. The This is a manufacturing method for lint wiring boards, and because the electrolytic plating process is used, the thickness of the metal layer can be set easily. Therefore, the conductive paste is sufficiently compressed, and a printed wiring board having a low connection resistance value and a highly reliable interlayer connection can be obtained.
[0044]
Claims of the invention 12 In particular, the step of forming a circuit of the metal foil is characterized in that the metal foil is dissolved and removed using an alkali etching solution mainly composed of copper ammonium complex ions. The This is a method of manufacturing a lint wiring board, and when a metal layer to be an etching resist is formed by electrolytic nickel plating, the metal foil is dissolved and removed while protecting the electrolytic nickel plating layer when etching with an alkaline etching solution. The effect that a circuit can be formed is obtained.
[0045]
Also book The invention is particularly characterized in that the metal layer is formed in a rectangular cross section. The This is a method of manufacturing a lint wiring board, and when the interlayer adhesive sheet is compressed and the circuit and the metal layer are embedded in the interlayer adhesive sheet, the resin of the interlayer adhesive sheet wraps around the circuit and the metal layer. Since the embedded metal layer is wider than the upper width of the circuit, an effect that the peel strength and pull strength can be significantly improved by the anchor effect can be obtained.
[0046]
Claims of the invention 13 In particular, the invention described in (1) is characterized by including a step of removing the support substrates of the first and second transfer plates after the step of heating and pressurizing. The This is a manufacturing method for lint wiring boards, so that even if foreign matter adheres to the substrate in the process of heating and pressurizing with a vacuum heat press or the like, the wiring pattern is protected by the metal foil that becomes the wiring pattern or the supporting substrate. The effect that the damage to the metal foil that leads to disconnection of the metal can be prevented is obtained.
[0047]
Claims of the invention 14 In particular, the invention described in (2) is characterized in that the step of removing the support substrate is chemical dissolution removal or mechanical polishing removal. The It is a manufacturing method of a lint wiring board, whereby the support substrate can be chemically dissolved with sulfuric acid, hydrochloric acid or the like, or can be easily removed at a relatively low cost using mechanical polishing with a belt sander or the like. An effect is obtained.
[0048]
Claims of the invention 15 In particular, the support substrate is characterized in that the support substrate is a conductor. The This is a method for manufacturing a lint wiring board, whereby the support substrate is a conductor, so that it is possible to easily form a metal foil such as copper foil on the support substrate by electrolytic plating.
[0049]
Claims of the invention 16 In particular, the support substrate is a resin film. The This is a method for manufacturing a lint wiring board, and by using a support substrate as a carrier, it is easy to handle in ultra-thin copper foil manufacturing equipment and transport and can be easily peeled off by a peeling machine. It is done.
[0050]
Claims of the invention 17 In particular, the invention described in (2) is characterized in that the resin film has heat resistance and releasability. The This is a method for manufacturing a lint wiring board, whereby even if heated and pressed by a vacuum hot press, the resin film that is a support substrate has heat resistance, so that welding can be prevented. Moreover, when removing a support substrate, it has the releasability and the effect that peeling and peeling become easy is acquired.
[0051]
Also book In particular, the step of preparing the interlayer adhesive sheet includes a step of forming a through hole in the interlayer adhesive sheet and filling with a conductive paste. The This is a manufacturing method of a lint wiring board, and when it is multi-layered, it is possible to conduct electricity only between necessary layers between arbitrary layers. Since it does not occur, the effect of achieving high density can be obtained.
[0052]
Claims of the invention 18 In particular, the invention described in 1) is characterized in that the interlayer adhesive sheet is an aramid nonwoven fabric epoxy resin-impregnated sheet having compressible porosity, and the impregnated resin is in a semi-cured state. The This is a method for manufacturing a lint wiring board, whereby an aramid nonwoven fabric epoxy resin impregnated sheet has a smaller specific gravity than a conventional glass cloth epoxy resin impregnated sheet, and thus the substrate becomes light and effective in reducing the weight of the product.
[0053]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment)
Embodiments of the present invention will be described below with reference to the drawings.
[0054]
1 and 2 are manufacturing process diagrams of a printed wiring board according to an embodiment of the present invention.
[0055]
First, a transfer plate 1 comprising a copper foil 3 as a metal foil and a support substrate 2 is prepared. The support substrate 2 is made of a conductive material such as a stainless steel plate or aluminum foil, and the support substrate 2 is made of a copper foil 3 formed by electrolytic plating, and the support substrate 2 is made of a resin film. In some cases, the resin film is laminated with copper foil (FIG. 1A).
[0056]
The copper foil 3 is preferably an ultrathin copper foil 3 having a thickness of 10 μm or less in order to form a fine wiring pattern 6 (about 30 to 50 μm) by etching.
[0057]
Next, a plating resist 4 is formed on the surface of the copper foil 3 formed on the support substrate 2 by a photo process (FIG. 1B).
[0058]
Next, an electrolytic nickel plating layer 5 having a rectangular cross section as a metal layer is formed in a portion where the plating resist 4 is not formed (FIG. 1C). Since the electrolytic nickel plating layer 5 has a relatively high hardness, it can be easily embedded in the interlayer adhesive sheet by heating and pressurizing in a subsequent process.
[0059]
Next, the plating resist 4 is peeled off with a solution such as sodium hydroxide (FIG. 1D). Then, by using the electrolytic nickel plating layer 5 as an etching resist and removing an unnecessary copper foil with an alkaline etching solution mainly composed of copper ammonium complex ions to form a predetermined wiring pattern 6, a first transfer plate is obtained. 1 is completed (FIG. 1E).
[0060]
The reason for dissolving and removing the copper foil using an alkaline etching solution mainly composed of copper ammonium complex ions is that the copper foil is dissolved and removed while protecting the electrolytic nickel plating layer 5 as an etching resist. It is because it can form.
[0061]
Next, a second transfer plate 10 in which different wiring patterns 9 are formed on the support substrate 7 is manufactured by the same transfer plate manufacturing method as described above (FIG. 1F), and the first and second transfer plates. Complete 1 and 10 preparations.
[0062]
Next, a porous substrate 12 having a release film 11 such as polyester on both sides is prepared. As the porous substrate 12, an aramid nonwoven fabric epoxy resin-impregnated sheet having a thickness of 50 to 100 μm is used (FIG. 2G).
[0063]
Since the aramid nonwoven fabric epoxy resin impregnated sheet has a small specific gravity, it is effective for reducing the weight. Aramid non-woven fabrics are suitable for opening minute holes at high speed because of their good laser processability. Furthermore, since the aramid nonwoven fabric is a resin and has good adhesion to the epoxy resin, the occurrence of bleeding due to the flow of the conductive paste is greatly reduced.
[0064]
In addition, if the resin content is in the range of 40 to 65%, one having excellent physicomechanical characteristics and electrical characteristics as a substrate can be selected, but it is desirable to select one having 55 to 60%. It is good. As a result, when the porous base material 12 is compressed, the resin wraps around the wiring pattern 9 and the metal layer, so that a substrate having excellent flatness without voids can be obtained.
[0065]
When an aramid nonwoven fabric epoxy resin-impregnated sheet as an interlayer adhesive sheet is selected in the range of 40 to 65% of the resin content described above, the compressibility of the porous substrate 12 is in the range of 10 to 50% and 55 to 60 When selected in the range of%, the compression rate can be set to 30 to 40%.
[0066]
Here, when the compressibility is 10% or less, the densification of the conductive material in the conductive paste is poor, and when the diameter of the through hole is a small diameter of 50 μm, the connection resistance value is increased, and the compressibility is In the case of 50% or more, the conduction hole is deformed, the smoothness of the base material is impaired, and the variation in resistance value tends to increase, which is inappropriate.
[0067]
Therefore, by selecting an aramid nonwoven fabric epoxy resin impregnated sheet as an interlayer adhesive sheet having a resin content in the range of 55-60% and a compressibility in the range of 30-40%, a physical machine as a substrate A substrate having excellent flatness can be obtained with a stable conductive connection resistance value as well as electrical characteristics and electrical characteristics.
[0068]
Next, a through hole 13 having a diameter of 50 to 100 μm is formed in a predetermined portion of the aramid nonwoven fabric epoxy resin impregnated sheet with a laser processing machine or the like (FIG. 2H), and the conductive paste 14 is filled into the through hole 13. As a filling method, an aramid nonwoven fabric epoxy resin-impregnated sheet having through-holes 13 is set on a screen printer or the like, and then the conductive paste 14 is printed directly on the releasable film 11.
[0069]
Next, after the release film 11 is peeled from both surfaces of the aramid nonwoven fabric epoxy resin impregnated sheet (FIG. 2 (I)), the first transfer plate 1 and the second transfer plate 10 that have been prepared are made to face each other. An aramid nonwoven fabric epoxy resin impregnated sheet as an interlayer adhesive sheet filled with the conductive paste 14 is overlaid (FIG. 2 (J)).
[0070]
Thereafter, the aramid nonwoven fabric epoxy resin impregnated sheet is compressed by heating and pressurizing from both sides of the first and second transfer plates with a vacuum heat press, and the wiring patterns 6 and 9 are placed inside the aramid nonwoven fabric epoxy resin impregnated sheet. And the electrolytic nickel plating layers 5 and 8 are embed | buried and adhere | attached with an aramid nonwoven fabric epoxy resin impregnation sheet | seat (FIG. 2 (K)).
[0071]
By making the support substrates 2 and 7 used for the first transfer plate 1 and the second transfer plate 10 into resin films having heat resistance and releasability, ultrathin copper foil on the support substrates 2 and 7 is used. Handling becomes easy in manufacturing equipment and conveyance, welding can be prevented even during heating and pressurization in a vacuum hot press, and the support substrates 2 and 7 can be easily removed and peeled off.
[0072]
Finally, the support substrates 2 and 7 are removed by chemical dissolution such as sulfuric acid and hydrochloric acid, or removal using a method that can be easily performed at low cost such as mechanical polishing such as a belt sander. A wiring board in which the nickel plating layers 5 and 8 are embedded in an aramid nonwoven fabric epoxy resin impregnated sheet is obtained (FIG. 2 (L)).
[0073]
Here, the relationship with the electrolytic nickel plating layer 5 as a metal layer embedded in the aramid nonwoven fabric epoxy resin impregnated sheet as an interlayer adhesive sheet will be described below.
[0074]
The aramid nonwoven fabric epoxy resin-impregnated sheet is 50 μm in thickness and 30 to 40% in compressibility, and the diameter of the through-hole 13 to be formed is set to 50 μm.
[0075]
In addition, in order to set the line width between the wiring patterns 6 and 9 on the first transfer plate 1 and the second transfer plate 10 to 30 μm, a copper foil 3 having an extremely thin thickness of 5 μm is used.
[0076]
At this time, the thickness of the electrolytic nickel plating layer 5 as the metal layer is set to 2.5 to 5 μm, which is 5 to 10% of the thickness of the interlayer adhesive sheet, so that the depth embedded in the interlayer adhesive sheet is set. Is 7.5 to 10 μm on each side, and stable pressing can be performed within a compression rate of 30 to 40% of the aramid nonwoven fabric epoxy resin impregnated sheet.
[0077]
Further, the thickness of the interlayer adhesive sheet is 100 μm (compressibility is 30 to 40%), the diameter of the through-hole 13 to be formed is 100 μm, the line spacing between the wiring patterns 6 and 9, and the line width is 50 μm. Even when the thickness of the copper foil 3 is 10 μm, the thickness of the electrolytic nickel plating layer 5 is set to 5 to 10 μm, which is 5 to 10% of the thickness of the interlayer adhesive sheet. Similar connection reliability effects can be obtained.
[0078]
Thereby, for finer, even if the thickness of the wiring patterns 6 and 9 is reduced, a metal layer with a certain thickness is embedded inside the base material, so that the conductive paste is sufficiently compressed, A printed wiring board having a low connection resistance value and a highly reliable interlayer connection can be obtained.
[0079]
If the thickness of the copper foil 3 is 10 μm or more, it becomes difficult to form a wiring pattern by etching. Conversely, if the thickness is 5 μm or less, it is difficult to transport and handle in the manufacturing process, which further increases the material cost. Poor nature.
[0080]
When such an extremely thin copper foil is used, the support substrates 2 and 7 of the first and second transfer plates are made of a conductive material such as an aluminum foil so that the support substrates 2 and 7 can be easily plated by electrolytic plating. In addition, it is possible to form a metal foil such as copper foil, and the handling becomes easy by using the ultrathin copper foil support substrates 2 and 7 that are difficult to handle in manufacturing equipment and transportation as a carrier. .
[0081]
In addition, since the dimensions are stabilized by fixing the base material with the support substrates 2 and 7, there is a positional accuracy defect due to the expansion and contraction of the base material, which has been a problem mainly in the heat treatment process during the manufacturing process. Decrease.
[0082]
Furthermore, it is desirable that the size of the electrolytic nickel plating layer 5 be 40 to 150 μm larger than the conduction hole, and the conductive paste 14 in the through-hole 13 covers the electrolytic nickel plating layer 5 even if a positional shift occurs during lamination. Since it is in a broken state, the conductive paste 14 becomes difficult to be exposed, and an allowable amount of displacement is increased. Further, since the metal layer having a wide rectangular cross section is embedded in the base material, the peel strength and the pull strength are greatly improved by the anchor effect.
[0083]
Here, when it is 40 μm or less, it is difficult to cope with the positional deviation, and when it is 150 μm or more, the wiring capacity in the wiring design is deteriorated, so the above range is desirable.
[0084]
As described above, according to the present embodiment, the compressibility of the conductive paste 40 has conventionally changed depending on the thickness of the copper foil as shown in FIGS. 3A and 3B. ) Even if the copper foil as the wiring pattern is thinned, the thickness of the conductor layer embedded in the base material is reduced by electrolysis because the electrolytic nickel plating layer as the metal layer is formed on the copper foil. It can be determined by the thickness of the nickel plating layer, and the compressibility of the conductive paste can be controlled by the thickness of the electrolytic nickel plating layer. A printed wiring board having a low value and high reliability can be obtained.
[0085]
In addition, as shown in FIG. 4A, the conductive paste is conventionally exposed 15 due to misalignment, but in this embodiment, it has a rectangular cross section as shown in FIG. 4B. Since the electrolytic nickel plating layer is formed, the conductive paste is difficult to be exposed, and the tolerance for displacement is increased.
[0086]
【The invention's effect】
As described above, according to the present invention, the wiring pattern formed on the substrate and the metal layer formed thereon are embedded in the base material to fill the through holes provided at predetermined positions on the base material. The conductive paste in the conductive paste is sufficiently compressed, and the conductive material in the conductive paste is densified, so that a printed wiring board having a low connection resistance value and a highly reliable interlayer connection is realized. Can do.
[Brief description of the drawings]
FIG. 1 is a process cross-sectional view illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention.
FIG. 2 is a process cross-sectional view illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view for comparing the compressed state of the conductive paste in the embodiment of the present invention.
FIG. 4 is a cross-sectional view for comparing interlayer connection states when the interlayer position is shifted in the embodiment of the present invention.
FIG. 5 is a process sectional view showing a conventional method of manufacturing a printed wiring board.
FIG. 6 is a process cross-sectional view illustrating a conventional method for manufacturing a printed wiring board.
FIG. 7 is a process cross-sectional view illustrating a conventional method for manufacturing a printed wiring board.
[Explanation of symbols]
1,10 transfer plate
2,7 Support substrate
3 Copper foil
4 Plating resist
5,8 Electrolytic nickel plating layer
6, 9, 34, 36 Wiring pattern
11 Releasable film
12,38 Porous substrate
13 Through hole
14, 40 conductive paste
15 Flow of conductive paste (exposure of conductive paste)

Claims (18)

A circuit having a metal layer with a rectangular cross section at the top is embedded from both sides of the interlayer adhesive sheet so that the metal layer faces the opposite direction,
A conduction hole for electrically connecting the metal layers embedded from both sides of the interlayer adhesive sheet;
The conductive hole is formed by compressing the conductive paste filled in the through hole of the interlayer adhesive sheet from both sides by the circuit having the metal layer on the upper part,
The width of the metal layer is larger than the width of the circuit at the contact surface between the circuit and the metal layer.   The printed wiring board according to claim 1, wherein the metal layer is formed by electrolytic plating.   The printed wiring board according to claim 1, wherein the constant thickness of the metal layer is 5 to 10% of the thickness of the interlayer adhesive sheet.   The printed wiring board according to claim 1, wherein the interlayer adhesion sheet is an aramid nonwoven fabric epoxy resin impregnated sheet.   2. The printed wiring board according to claim 1, wherein the dimension of the metal layer is 40 to 150 [mu] m larger than the conduction hole.   The printed wiring board according to claim 1, wherein the interlayer adhesive sheet is a porous material having compressibility.   The printed wiring board according to claim 6, wherein the compressibility of the porous material having compressibility is 10 to 50%.   The printed wiring board according to claim 1, wherein the resin content of the interlayer adhesive sheet is 40 to 65%. Preparing first and second transfer plates having metal foil formed on a support substrate;
Selectively forming a metal layer having a rectangular cross section on metal Ku of the first and second transfer plates,
Forming a circuit by etching the metal foil until the width of the metal foil at the contact surface between the metal layer and the metal foil is smaller than the width of the metal layer. ,
Preparing a sheet for interlayer adhesion;
Laminating to face the circuit forming surface of the first and second transfer plate through the interlayer adhesive sheet,
Comprising a pressurized heat-pressurizing step,
The step of preparing the interlayer adhesive sheet includes a step of forming a through hole in the interlayer adhesive sheet and a step of filling the through hole with a conductive paste .   10. The printed wiring board according to claim 9, wherein in the step of selectively forming the metal layer, a plating resist is formed by a photo process, and an electrolytic nickel plating layer is formed in a portion where the plating resist is not formed. Method.   The thickness of a metal layer is set to 5 to 10% of the thickness of the sheet | seat for interlayer adhesion using an electrolytic plating process, The manufacturing method of the printed wiring board of Claim 9 characterized by the above-mentioned.   10. The method for producing a printed wiring board according to claim 9, wherein the step of forming the metal foil in a circuit comprises dissolving and removing the metal foil using an alkaline etching solution mainly composed of copper ammonium complex ions.   The method for manufacturing a printed wiring board according to claim 9, further comprising a step of removing the support substrates of the first and second transfer plates after the pressurizing and heating step.   The method for manufacturing a printed wiring board according to claim 13, wherein the step of removing the support substrate is chemical dissolution removal or mechanical polishing removal.   The method for manufacturing a printed wiring board according to claim 9, wherein the support substrate is a conductor.   The method for manufacturing a printed wiring board according to claim 9, wherein the support substrate is a resin film.   The method for producing a printed wiring board according to claim 16, wherein the resin film has heat resistance and releasability.   The method for producing a printed wiring board according to claim 9, wherein the interlayer adhesive sheet is an aramid nonwoven fabric epoxy resin-impregnated sheet having compressible porosity, and the impregnated resin is in a semi-cured state.

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