JP3049972B2 - Multilayer wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for connecting upper and lower circuits of a multilayer wiring board.

[0002]

2. Description of the Related Art A multilayer wiring board can incorporate a signal circuit, a power supply, an earth circuit, and the like, and is therefore often used in various electronic devices as an effective method for increasing the wiring density. A typical method of manufacturing a conventional multilayer printed wiring board is to cover the portions other than the interconnections with a coverlay film or the like and obtain electrical insulation, and electrically connect the wiring patterns of each layer to each other by copper plating or the like. It has been done. In addition, as a relatively new attempt, the interconnects are covered with conductive particles while obtaining insulation by covering other than the interconnects with a coverlay film, mask film, resist film, etc. (collectively referred to as cover films hereinafter). It has also been proposed to connect the wiring patterns of each layer to each other using a material made of a dispersed adhesive (for example, Japanese Patent Application Laid-Open No. 61-49499 and Japanese Patent Application Laid-Open No. 2-3659).
No. 3), and solder particles are used as the conductive particles in this case.

[0003]

In any of the above-mentioned conventional methods, since the portions other than the interconnecting portions are covered with a cover film, it is difficult to reduce the thickness of a multilayer wiring board, which hinders the reduction in thickness. Pressing the cover film to the necessary part is one of the causes of cost increase. As for the interconnection method of the wiring patterns, the method of plating with copper or the like requires a complicated plating step, and has a disadvantage that the copper plating is easily broken when the cover film is thermocompressed. When connecting with a material consisting of conductive particles and an adhesive, since the conductive particles are uniformly dispersed throughout the bonding, the adhesive flows due to thermocompression bonding at the time of connection, and other than the parts that require connection of the wiring pattern However, when the conductive particles are solder, it becomes impossible to cope with the increasingly thinning of the wiring, especially when the conductive particles are melted and connected and leaked in the adjacent wiring pattern. The present invention relates to a multilayer wiring board using an interlayer connection which does not require a cover film or a plating step and can cope with thinning of wiring.

[0004]

According to the present invention, at least one of opposing wiring patterns between a plurality of double-sided wiring boards each having a wiring pattern formed on an insulating substrate is protruded from the substrate surface and the other wiring board is formed. The present invention relates to a multilayer wiring board in which opposing wiring boards other than wiring patterns which need to be connected and contact with the above wiring pattern are laminated and integrated with an adhesive. Sand
That is, the present invention comprises forming a wiring pattern on an insulating substrate.
Minimize double-sided wiring patterns on multiple double-sided wiring boards
One of them protrudes from the board and the wiring pattern of the other wiring board
Opposite wiring board other than wiring pattern that needs to be connected
A multi-layer printed wiring board that is laminated and integrated with an adhesive
At least one surface of the wiring pattern has a surface roughness
When forming a fine uneven surface of 0.2 to 20 μm
Grain structure of plating, chemical etching and plasma etching
Roughness, roughening due to mechanical polishing, fine irregularities on the wiring pattern
It is formed by pressure stamping on the surface, and the adhesive is
A multilayer printed wiring board which does not contain any.

The configuration of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view illustrating an embodiment of the present invention. Reference numeral 1 denotes an insulating substrate made of phenolic resin, epoxy resin, polyimide, etc., paper, glass cloth, glass nonwoven fabric,
Or the like, which is impregnated into a base material such as polyester, heated and pressed, a plastic film such as polyester or polyimide, a metal such as Al or Fe, and a ceramic.

The wiring pattern 2 is formed on both sides of the insulating substrate 1 as shown in FIG. 1, but the outermost layer when a multilayer wiring board is formed may be a single-sided board without a wiring pattern. It is necessary that at least one of the opposed wiring patterns 2 protrudes from the substrate surface as shown in FIG. The other opposing wiring pattern may be in a protruding shape, a flat shape as shown by 2 'in FIG. 2, or a concave shape (not shown). It is preferable that the height of the wiring pattern after connection be uniform and planar, from the viewpoint of improving the reliability of the connection portion. These wiring patterns can be formed by general means such as a tenting method, an additive method, and a transfer method. It is preferable that at least the surface of the wiring pattern that requires connection has minute irregularities. Examples of the method of obtaining the fine irregularities include a grain boundary structure of plating at the time of forming a wiring pattern, etching with a chemical solution or plasma, roughening by mechanical polishing, and pressure stamping of a fine irregularity surface on a wiring pattern. Can be illustrated. The unevenness is preferably about 0.2 to 20 μm in surface roughness. When the thickness is less than 0.2 μm, the adhesive from the contact interface is hardly removed, and sufficient contact between the wiring patterns cannot be obtained. If it is 20 μm or more, it is difficult to form highly accurate unevenness, and it is also difficult to obtain a fine wire connection. For these reasons, the thickness is more preferably 0.5 to 10 μm.

[0007] An adhesive layer may exist between the insulating substrate 1 and the wiring pattern 2. The presence of the adhesive layer is preferable because it acts as a cushion layer at the time of connection and the connection portion becomes uniform. In the interlayer connection method, an adhesive 5 is arranged between first and second wiring boards 3 and 4 having a wiring pattern 2 requiring connection, laminated and integrated with the adhesive, and the two circuit boards are bonded to each other. At the same time, electrical continuity between the wiring patterns requiring these connections is obtained. The wiring pattern 2 that needs to be connected here may be the entire pattern or a part of the pattern, and a connection-free wiring pattern 6 (for example, a via hole) may be present on the connection surface.

The adhesive 5 may be in the form of a film as shown in FIG. 1 or may be formed by applying a liquid material to one of the wiring pattern surfaces by coating or printing as shown in FIG. When the film is in the form of a film, it is easy to handle and can be supplied at a constant thickness, so that it is not necessary to apply an adhesive, which is preferable. As the adhesive 5, a thermoplastic material used for a sheet or the like,
A curable material using energy such as heat, light, and an electron beam can be widely applied. Curable materials are preferred because they have excellent heat resistance and moisture resistance of the multilayer wiring board.Epoxy-based adhesives and imide-based adhesives have excellent adhesiveness and heat resistance due to their molecular structure, and can be set over a wide range of curing times. Is preferred.

The epoxy-based adhesive contains, for example, a high-molecular-weight epoxy, a solid epoxy and a liquid epoxy, an epoxy modified with urethane, polyester, NBR, or the like as a main component, and is added with a curing agent, a catalyst, a coupling agent, a filler, and the like. Is common. When these materials are high-purity products in which Na ions and Cl ions of the extraction water are 20 ppm or less, it is preferable that the electric corrosion resistance of the multilayer wiring board is improved.
Conventionally, a prepreg composed of an epoxy-based or imide-based adhesive and an inorganic filler such as glass fiber, which has been widely used for a multilayer wiring board, has a problem in that the inorganic filler hinders contact between wiring patterns and does not provide sufficient conductivity, and the multilayer Since it is difficult to reduce the thickness when the wiring board is used, it is not preferable for implementing the present invention. If a filler is included, it should be melted or softened at least under the connection conditions, or be buried in fine irregularities on the surface that requires connection of the wiring pattern, so as not to hinder contact between the wiring patterns. .

At the time of lamination and integration, a portion of the wiring pattern surface that requires connection is positioned and heated and pressed. At this time, a so-called pin lamination method in which, for example, a through-hole is formed in a predetermined number of wiring boards that require lamination and alignment is performed with pins or the like is preferable. As a method of integration, a general method such as pressing or a roll laminator is used. Good way. Electrical connection between all layers can also be obtained by plating the through-holes of the pin lamination method with through-holes or filling them with a conductive adhesive.

FIG. 3 is a sectional view showing the structure of FIG. 1 after lamination and integration. Due to the heating and pressing, the portions 2-2 'on the wiring pattern which need to be connected come into contact with each other to enable electrical connection, and the adhesive flows to fill and bond between the two substrates 1-1'. The connection unnecessary wiring pattern 6 is kept insulative. By arbitrarily laminating this layer, an arbitrary multilayer wiring board can be obtained. Although the optimum filling amount of the adhesive can be controlled by the thickness of the adhesive, it is preferable that the unnecessary portion is removed by flowing out to the end by laminating and integrating, so that air bubbles are less mixed.

[0012]

According to the present invention, at least one of the opposing wiring patterns protrudes from the substrate surface and comes into contact with another wiring pattern to form an interconnecting portion. To be laminated and integrated. Therefore, the surface of the wiring board other than the interconnecting portion is in contact with the insulating adhesive, so that a cover film is not required, and no leak occurs between adjacent patterns. Since the interconnections are electrically connected by contact between the wiring patterns, plating is unnecessary. Further, since the wiring patterns are in contact with each other, the resistance of the connection portion is low. Since the connecting portion does not use conductive particles, the conditions of thermocompression bonding can be widely applied. Therefore, the connection resistance is stabilized, the reliability is improved, and it is possible to cope with the thinning of the circuit. In addition, a multilayer wiring board which is effective in reducing the thickness and cost of the multilayer wiring board can be obtained very easily.

[0013]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In addition, for simplicity of description, a four-layer wiring board in which two double-sided boards are connected to each other will be described. However, one of the two double-sided boards may be a single-sided board, and a multilayer wiring board having more than four layers may be used. Applicable.

Examples 1-4 Adhesive 1 was applied to both sides of a glass epoxy substrate having a thickness of 0.2 mm.
With respect to a double-sided substrate having a copper foil of 18 μm formed through 0 μm, four types of wiring boards having different wiring pattern surfaces which require connection by pattern printing and etching were prepared.
The minimum width of the wiring pattern that requires these connections is 50
μm. Electrolytic foil (Rz =
0.8 μm, Example 1), double-sided electrolytic foil (Rz = 7.3 μm)
m, Example 2), surface Sn plating of a rolled foil (Rz = 3.
5 μm, Example 3) and surface plasma etching of the rolled foil (Rz = 2.2 μm, Example 4). Where Rz
Is JIS. B0601 10-point average roughness (reference length 0.
8 mm). An adhesive having a high molecular weight epoxy as a main component and having a thickness of 30 μm (each of Na ion and Cl ion of extracted water after extraction at 100 ° C. for 10 hours with pure water, each having a Na ion and a Cl ion of 10 ppm or less) was formed on a separator obtained by treating a polyester film with a release agent. . The wiring pattern that requires one connection of the wiring board and the other wiring pattern are aligned with the same processing surface facing each other, lightly pressed with a roll, the separator is peeled off, and the other wiring board is aligned. And 180 ℃ 3
0 kg / cm ² For 30 minutes to cure the adhesive. Excess edge portions were removed to obtain a four-layer wiring board in which two double-sided boards were connected in layers. Examples 1 to 4 all showed sufficient interlayer connection characteristics. When the cross section of the connection portion was observed with a scanning electron microscope, the irregularities on the surface of the wiring pattern were in contact.

Examples 5 to 6 The same as Examples 1 to 4, but the combination of the wiring patterns facing each other was changed. In Example 5, the electrolytic foil of Example 1 was opposed to the double-sided electrolytic foil of Example 2. Example 6 is Example 1
And the surface Sn plating of Example 3 were opposed to each other. Examples 5 to 6 all showed sufficient interlayer connection characteristics.

[0016]

As described above, according to the present invention, a cover film and a plating step are not required, and it is possible to cope with thinning of a circuit, and in addition, a connection effective for reducing the thickness of a multilayer wiring board and reducing costs. A multilayer wiring board with improved reliability can be obtained very reasonably easily.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the configuration of the present invention.

FIG. 2 is a schematic sectional view showing an embodiment of the configuration of the present invention.

FIG. 3 is a schematic sectional view showing one embodiment of the present invention after lamination and integration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating board 2 Wiring pattern 3 First wiring board 4 Second wiring board 5 Adhesive 6 Connection-free wiring pattern

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kyohisa Ota 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (56) References JP-A-54-44765 (JP, A) JP-A-3-289195 (JP, A) JP-A-63-53994 (JP, A) JP-A-2-226788 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/46

Claims (1)

(57) [Claims] At least one of the double-sided wiring patterns of a plurality of double-sided wiring boards having a wiring pattern formed on an insulating substrate projects from the substrate and comes into contact with the wiring pattern of another wiring board, thereby requiring wiring. A multilayer printed wiring board in which opposing wiring boards other than patterns are laminated and integrated with an adhesive.
At least one surface of the wiring pattern has a surface roughness
When forming a fine uneven surface of 0.2 to 20 μm
Grain structure of plating, chemical etching and plasma etching
Roughness, roughening due to mechanical polishing, fine irregularities on the wiring pattern
It is formed by pressure stamping on the surface, and the adhesive is
A multilayer printed wiring board which does not contain any.