JP2007194554A - Manufacturing method of hybrid multilayer circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a hybrid multilayer circuit board where a burr is not made during processing of through-holes, and the surface of a copper foil of an outer layer material in the case of stacking is protected from sticking of a foreign matter in the manufacturing method of the hybrid multilayer circuit board. <P>SOLUTION: In the manufacturing method of the hybrid multilayer circuit board having a structure where a cable B is pulled out from a multilayer part A; a resin coat 5 is formed on the surface of the copper foil of the outer layer at a multilayer and the through-holes 61 and 62 are worked with a drill through the resin coat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a circuit board used in an electronic device, and more particularly to a method for manufacturing a hybrid multilayer circuit board having a structure in which a cable part is drawn from a multilayer part on which a component is mounted.

  As a hybrid multilayer circuit board having a structure in which a cable part is drawn out from a multilayer part to be mounted with a component, there is a rigid flex wiring board in which a rigid printed board is bonded to both surfaces (see Patent Document 1). There is also a multilayer flexible printed circuit board in which a plurality of flexible printed circuit boards are bonded together. These are referred to as hybrid multilayer circuit boards.

  One method for manufacturing a hybrid multilayer circuit board is shown in FIGS. As shown in FIG. 8, the inner layer core substrate 4 formed in advance and the outer layer material having the copper foil 1 and the insulating film 2 obtained by punching and removing the portion corresponding to the portion B to be the cable portion, It laminates | stacks like FIG. 9 through the adhesive member 3 which stamped and removed the same location as outer layer material.

  In the hybrid multilayer circuit board formed by this method, the adhesive member component flows out at the boundary portion C between the multilayer portion A and the cable portion B on which the component is mounted, and as shown in FIG. It becomes a shape.

  When a through hole is processed after stacking, a plurality of hybrid multilayer substrates are overlapped as shown in FIG. 11, but a gap is formed near the boundary E between the multilayer part A and the cable part B. When drill holes are drilled in this state, as shown in FIG. 11, there is no problem with the through-hole 61 that is opened at the position where it is in close contact with the upper and lower hybrid multilayer circuit boards. The burr and burr as shown by the portion F in FIG. This is because when the drill is inserted, there is a force for pushing or pulling up the material on the outside.

  Such burrs and burr protrusions may damage the etching resist film and break the pattern when a pattern is formed by bonding the etching resist film to the surface. For this reason, a mechanical removal method such as polishing is usually employed.

  In this case, in the hybrid multilayer circuit board, when removing burrs and burr by polishing, the boundary portion C between the multilayer portion A and the cable portion B is a place where there is a step and the polishing member is difficult to follow and difficult to hit, Furthermore, since the section D in FIG. 10 has a slope-like cross-sectional shape, it is necessary to press the polishing member more strongly. However, if the polishing member is pressed too strongly, the outer layer copper foil 1 is more strongly polished, resulting in a problem that the thickness of the copper foil is reduced or deep flaws are generated.

  For example, Patent Document 1 proposes the use of a cushioning material at the time of stacking as a method of relieving the plate thickness variation that results in a slope-like cross-sectional shape. However, it is impossible to completely prevent variations in plate thickness.

  As a method for removing burrs and burr, there is a method in which a hole is formed after a protective film is applied and then removed by side etching by dipping or spraying in an etching solution (see Patent Document 2). However, when it is applied to a multilayer circuit board, the inner layer circuit is side-etched, causing migration.

  As a method for suppressing burrs when forming a through hole in a recess, there is a method of drilling a hole by placing an elastically deformable auxiliary sheet on the recess (see Patent Document 3). However, merely placing the auxiliary sheet only has an effect of suppressing burr on the concave portion on the upper surface, and does not follow the gap when the mixed multilayer circuit board shown in FIG. Can not respond.

  In addition to the problem of burr and burr, if foreign matter adheres to the surface of the copper foil 1 which is an outer layer material during lamination, it may be fixed by pressing and may cause a short circuit during circuit formation. Examples of the main foreign material include a peeled piece of the resin component from the punched portion of the adhesive member in which the position to be the cable portion is punched and removed. It is also necessary to protect the surface of the copper foil 1 from these foreign substances.

  In order to protect the copper foil surface of the outer layer material, there is a method in which a thermoplastic resin sheet is stacked and pressed (see Patent Document 4). In this patent document 4, it is said that this thermoplastic resin sheet is also used as an etching resist.

However, when the thermoplastic resin sheet having a thermal deformation temperature of 120 ° C. or less described in Patent Document 4 is used for laminating a hybrid multilayer circuit board, the flow out to the cable portion is remarkable, so the boundary portion between the multilayer portion A and the cable portion B If it adheres with C, it will become difficult to remove later.
Japanese Patent Laid-Open No. 5-191050 JP-A-8-88454 JP 2005-81508 A JP 2001-177241 A

  As described above, conventionally, when a through hole is formed in a hybrid multilayer circuit board having a structure in which a cable portion is drawn out from the multilayer portion, there is a problem that burrs and burr are generated, and the copper foil surface of the multilayer portion is formed. There is a problem that an effective measure for preventing the adhesion of foreign matter is not taken.

  The present invention has been made in consideration of the above-mentioned points. First, in a method for manufacturing a hybrid multilayer circuit board having a structure in which a cable portion is drawn from a multilayer portion, burrs and burr are produced during the processing of through holes. It aims at providing the manufacturing method which does not produce.

  A second object of the present invention is to provide a method for manufacturing a hybrid multilayer circuit board that protects foreign matter from adhering to the copper foil surface of the outer layer material during lamination.

In order to achieve the above object, in the present invention,
In the manufacturing method of the hybrid multilayer circuit board having a structure in which the cable portion is drawn from the multilayer portion,
Forming a resin film on the copper foil surface of the outer layer in the multilayer part,
Drilling a through hole through the resin film, a method for producing a hybrid multilayer circuit board,
Is to provide.

  Here, the resin film may be formed by pasting together a film-like resin with an adhesive, but may be formed by curing a liquid resin applied by printing means. If the resin film is formed before processing the through hole, the drill hole processing itself does not require heat resistance, so select a resin that can be completely removed when removing from the copper foil surface to form the film. That's fine.

  According to the present invention, since the resin film is formed on the copper foil surface of the outer layer in the hybrid multilayer circuit board and the through hole is drilled through the resin film, not only the upper surface but also the lower surface is processed during the processing of the through hole. On the other hand, burr and burr can be suppressed.

  In addition, if the resin film to be formed on the outer layer copper foil surface is previously applied to the copper foil surface of the outer layer material, the resin film is removed after drilling a through hole by using it as it is after the lamination process. Further, it is possible to prevent foreign matters from adhering to the copper foil surface of the outer layer material at the time of lamination, and it is possible to suppress burrs and burr when processing through holes.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

Embodiment 1

  FIGS. 1 to 3 show Embodiment 1. As a film that uses a heat-resistant film as a resin film to prevent foreign matter from adhering to the surface of the copper foil during lamination, and as a film that suppresses burrs and burr when processing through holes. Here is an example of using.

  FIG. 1 is an exploded side view showing a state immediately before lamination of a hybrid multilayer circuit board according to the present invention. As shown in FIG. 1, a multilayer film A is formed by laminating a heat-resistant film 5 on the surface of a copper foil 1 which is an outer layer material having a copper foil 1 and an insulating layer 2, and a portion B which becomes a cable part is formed. Corresponding parts are punched and removed. And it laminates | stacks through the adhesive member 3 which punched and removed the same location.

  FIG. 2 shows a state after the lamination. The heat-resistant film 5 disposed on the outermost layer can prevent foreign matters from being caught on the surface of the copper foil 1. Then, drilling is performed with the heat resistant film 5 attached.

  Here, the heat resistance that the heat-resistant film 5 should have is one that can be completely removed when removed from the copper foil surface, and one that does not decompose, transform, or melt at a predetermined temperature during lamination. Say.

  After the lamination, since the heat-resistant film 5 is pressure-bonded to the surface of the copper foil 1, there is no gap on the surface of the copper foil 1 as shown in FIG. 3, and there is a gap between the upper and lower hybrid multilayer circuit boards. Even in the through-hole 62 opened in the place, the occurrence of burr and burr of the copper foil can be suppressed not only on the upper surface but also on the lower surface.

  Next, the heat-resistant film 5 is peeled off, and through hole plating or outer layer circuit formation is performed by a predetermined method to obtain a hybrid multilayer circuit board.

  As a heat-resistant film that prevents foreign matter from adhering to the surface of the copper foil during lamination, for example, when a prepreg made of polyimide resin is used in the lamination process, the softening point temperature is 170 ° C. Heat resistance at higher temperatures is required.

  As a material in this case, PET (polyethylene terephthalate) resin, PEN (polyethylene naphthalate) resin, polyimide resin, PPS (polyphenylene sulfide) resin, PMP (polymethylpentene) resin, or the like can be used.

  As a pressure-sensitive adhesive for laminating, for example, an acrylic pressure-sensitive adhesive, such as an alkyl (meth) acrylate or glycidyl (meth) acrylate, that can be peeled off without being left on the surface of the copper foil 1 even when heated and pressed. The main component can be used.

  If the thickness of the heat-resistant film is about 20 to 100 μm, it is possible to protect the surface of the copper foil during lamination and to prevent burrs and burr during drill hole processing. A sufficient pressure-bonding force can be obtained if the thickness of the pressure-sensitive adhesive is about 5 to 20 μm.

  As the resin film other than the heat-resistant film, alkali-soluble ink or solvent-soluble ink used for an etching resist or the like can be used. These films also preferably have a thickness of about 20 to 100 μm.

  In addition, if the resin film is formed before the through hole is processed, heat resistance is not particularly required, and for example, polyvinyl alcohol can be used in addition to the resin.

(Effect of Embodiment 1)
4 to 7 are photomicrographs showing the finished state around the through hole when the method according to the present invention is performed.

  FIG. 4 shows a state in which a through hole on the lower surface is viewed from above when a drill hole is processed with a heat resistant film laminated on a copper foil surface by the method of the present invention, and FIG. 5 shows a drill without laminating a heat resistant film. The state of the through hole on the lower surface when drilled is viewed from above.

  The through-hole when drilled with a heat-resistant film laminated shows almost no burr or burr (Fig. 4), whereas the through-hole when drilled without a heat-resistant film laminated is A Burrs are observed in the parts and the like (FIG. 5).

  FIG. 6 shows a cross section of the through hole when the drill hole is processed in the same manner in which the heat resistant film is laminated, and FIG. 7 shows a cross section of the through hole when the drill hole is processed without laminating the heat resistant film.

  Similarly, the through-hole when drilled with a heat-resistant film laminated shows almost no burrs or burr (Fig. 6), whereas the through-hole when drilled without a heat-resistant film laminated In FIG. 7, burrs are observed on the lower surface B part.

  Therefore, according to the method of the present invention, it is possible to establish a method for manufacturing a hybrid multilayer circuit board that suppresses burrs and burr not only on the upper side but also on the lower side during the processing of the through hole due to the presence of the resin film. . Further, if the resin film can withstand the temperature at the time of lamination, it is possible to protect the foreign material from being attached to the copper foil surface of the outer layer material.

  Conventionally, the substrates overlapped at the time of drilling may rub against each other and become scratched. However, this can be avoided by forming a resin film. Furthermore, the entry board has been arranged to prevent scratches when the pressure foot hits when drilling holes, but there is also an advantage that this is not necessary.

  And the outer-layer copper foil surface can also be protected from impurities such as insulating resin pieces generated from the through holes. If the resin film is formed from the time of lamination, the surface of the outer layer copper foil can be protected also from the peeled piece of the resin component from the punched portion of the adhesive member.

Embodiment 2

  In the first embodiment, a heat resistant film is used as a resin film as a heating measure at the time of lamination. However, when this heating is not performed, a resin film having no heat resistance can be used as the resin film.

The disassembled side view which showed the state just before lamination | stacking of the hybrid multilayer circuit board based on this invention. The side view which shows the state after lamination | stacking of the hybrid multilayer circuit board based on this invention. The side view which shows the structural example of the hybrid multilayer circuit board based on this invention. The microscope picture which shows the through-hole edge part when it drills in the state which laminated | stacked the heat-resistant film on the copper foil surface of the multilayer circuit board by this invention. The microscope picture which shows the through-hole edge part when drilling a hole without laminating a heat-resistant film on the copper foil surface by the conventional method. The microscope picture which shows the side cross section of a through hole when drilling a hole in the state which laminated | stacked the heat-resistant film by this invention. The microscope picture which shows the side cross section of the through hole when drilling a hole without laminating the heat-resistant film by the conventional method. The exploded side view which showed the state just before lamination | stacking of the conventional hybrid multilayer circuit board. The exploded side view which showed the state after the lamination | stacking of the conventional hybrid multilayer circuit board. The side view which showed the structure of the conventional hybrid multilayer circuit board. Explanatory drawing which shows the malfunction example in the conventional hybrid multilayer circuit board. Explanatory drawing which shows the other malfunction example in the conventional hybrid multilayer circuit board.

Explanation of symbols

1 copper foil, 2 insulating film, 3 adhesive member, 4 inner layer core substrate,
5 Resin film (heat-resistant film), 61, 62 Through hole.
A Multi-layer part, B cable part, C boundary part, D section.

Claims (4)

In the manufacturing method of the hybrid multilayer circuit board having a structure in which the cable portion is drawn from the multilayer portion,
Form a resin film on the copper foil surface of the outer layer in the multilayer part,
Drilling a through hole through the resin film. A method for producing a hybrid multilayer circuit board. In the manufacturing method of the hybrid multilayer circuit board according to claim 1,
On the surface of the copper foil in the multilayer portion, a resin film having heat resistance equal to or higher than the heating temperature at the time of lamination is formed,
Punching out the portion corresponding to the portion that becomes the cable portion in the material of the outer layer portion that has formed the resin film,
Laminating the inner layer core substrate formed in advance and the material of the outer layer part via an adhesive member in which a portion corresponding to the part to be the cable part is punched and removed in advance.
A method for manufacturing a hybrid multilayer circuit board. In the manufacturing method of the multilayer circuit board of Claim 1 or 2,
The method for producing a hybrid multilayer circuit board, wherein the resin film is formed by bonding a film-like resin with an adhesive. In the manufacturing method of the multilayer circuit board of Claim 1 or 2,
The method for producing a hybrid multilayer circuit board, wherein the resin film is formed by curing a liquid resin applied by printing means.