JPH04152597A - Manufacture of multilayer printed circuit board - Google Patents

Abstract

PURPOSE:To inexpensively manufacture a multilayer printed circuit board with high productivity by opening reference holes for aligning through an inner layer plate and a small flat plate, engaging it with a caulking tool, caulking a prepreg and the inner layer plate together, further laminating the prepreg and an outer layer copper foil, and integrally molding them. CONSTITUTION:A circular small flat plate 1 made of metal or resin is adhesively secured to an inner layer plate 3 formed with circuit patterns on front and rear surfaces by using adhesive 2, and an aligning reference hole is opened from above the plate 1. Then, an inner layer plate 3b is superposed on the plate 3 adhered with a washer 1 through a prepreg 4, an eyelet 5 is hammered in to the hole, and the plates 3, 3b and the prepreg 4 are caulked. Then, prepregs 6 are superposed on both side surfaces of a set (inner layer materials) of the caulked layers 3, 3b, outer layer copper foils 7 are further superposed on both sides, heated, and pressure molded integrally to manufacture a multilayer printed circuit board.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention arranges inner layer plates with high positional accuracy, and
The present invention relates to a method for manufacturing a multilayer printed wiring board that can be obtained with good workability and at low cost.

(Conventional technology) In recent years, as industrial electronic equipment has become faster and more dense, wiring boards that carry electronic components have become more multi-layered. There is an increasing demand for multilayer wiring boards.

Conventionally, such a multilayer wiring board, as shown in FIG.
For example, on both the front and back sides of the insulating plate 11, there are
Inner layer board 14 on which two wiring patterns 12 and 13 are formed
After stacking a plurality of sheets with an appropriate number of prepregs 15a sandwiched between them, and overlapping the prepregs 15b and outer layer copper foil 16 on both sides, the whole is heated and pressurized using a hot press (not shown) or the like, and molded into one piece. It is manufactured by In such a manufacturing method, alignment of the wiring patterns between the inner layer boards has conventionally been performed using various methods shown below.

<a> Pin lamination method Outer layer copper foil 16, inner layer board 14, prepreg 15a.

Guide holes (not shown) are drilled at the same pitch in all the predetermined positions to be laminated, such as 15b, and metal id pins are set up at a predetermined pitch on the mold surface of a special mold. This is a method of aligning the kite by inserting it into the kite hole.

(b) Multiple molding method (sequential method) First 4
After making the layered plates and completing the circuit, the inner layered plates are stacked one by one and molded, and this process is repeated as many times as necessary.

(C) Adhesive method After drilling holes for alignment in a plurality of inner layer plates 14 and prepreg 15a, stacking them and setting them in an alignment jig, use adhesive such as cyanoacrylate to bond the plates together. This is to glue and fix the space between them.

(d) Using HA I ~ Me instead of adhesive in the eyelet method adhesive method,
Fix it in the aligned position. That is, as shown in FIG. 5, the inner layer plate 14 and the prepreg 1'5a are aligned and stacked one on top of the other, and then the eyelet 17 is driven into the inner layer plate 14 and the prepreg 1'5a, and then the end portion 17a of the eyelet 7 is caulked to mechanically fasten This is a method to do so.

(Problems to be Solved by the Invention) However, these alignment and fixing methods have the following problems. That is, (a) the pin lamination method allows highly accurate positioning, but only a small press can be used, resulting in low productivity. Further, there is a problem in that it takes time to remove the pin after heating and pressure forming and to remove the resin attached around the pin. (b) The multiple molding method has the disadvantage that it takes time to manufacture the final multilayer wiring board, and it cannot meet the market demand for short delivery times. In addition, (c) the adhesive method not only does not have sufficient fixing strength, but also has the problem that the adhesive deteriorates when heated and pressurized, causing cracks or peeling at the fixed part, which tends to cause a decrease in alignment accuracy. .
(d) In the eyelet method, the eyelet 17 is thin and does not have sufficient strength, so when crimping, as shown in Figure 6,
Alternatively, when the outer layer copper foil 16 is stacked and heated and press-molded, bends or distortions occur in the hollow straight pipe portions of C1 to M17 due to the prepreg 15a, and the inner layer plate is drawn in, and as a result, There is a drawback that misalignment occurs between the inner layer conductors.

The present invention has been made in view of the above-mentioned circumstances, and is aimed at manufacturing multilayer printed wiring boards with high productivity and low cost, especially by aligning a plurality of inner layer boards with high precision and having six or more conductor layers. , it is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive research to achieve the above object, the present inventors have developed a hollow straight eyelet that is inserted into the alignment reference hole in the eyelet method. The present invention was completed based on the discovery that the above object can be achieved by placing a washer-like object along the outer wall of the tube and strengthening the eyelet wall surface.

That is, the present invention provides a multilayer Pnont wiring board consisting of a plurality of inner layer boards with inner layer wiring formed on both the front and back surfaces, a prepreg hardened layer, and outer layer wiring! To! The bonding method includes the step of bonding a small flat plate to a reference position of at least one of the plurality of inner layer plates, and the step of bonding the small flat plate to the reference position of the inner layer plate after the bonding step, and the step of bonding the inner layer plate to the reference position of the inner layer plate after the bonding step. A drilling step of drilling a reference hole for positioning that penetrates the small flat plate, and a caulking tool is inserted into the reference hole for positioning of the inner layer plate that has gone through the above drilling step, and together with the prepreg and other necessary inner layer plates. This is a method for manufacturing a multilayer printed wiring board, which includes a caulking process, and a molding process of laminating prepreg and, if necessary, an outer layer copper foil on the caulked inner layer board and integrally molding the same.

The inner layer plate, prepreg, and outer M#l foil used in the present invention are not particularly limited to the manufacturing method or raw materials for the present invention, and commonly used inner layer plates, prepreg, and outer layer copper foil may be used. Ru.

The small flat plate (also called a washer because it becomes washer-like after perforation) used in the present invention is not particularly limited in shape or material, and can be used.

Examples of the material of the washer include metals such as copper, brass, iron, and alloys thereof, and resins (both thermosetting resins and heat-resistant thermoplastic resins) such as epoxy resins, polyimide resins, and polyester resins. Examples of these resins include impregnated cured products obtained by impregnating and curing resins into glass cloth, nonwoven paper, etc., and products obtained by coating metals with these resins. Among these, it is desirable to use a material that does not generate dust, especially metal chips, when drilling the alignment reference hole. Since the thickness of the washer is used to prevent eyelet deformation during molding, it is desirable that the thickness of the washer be equal to the distance dimension between the inner layer plates.

The outer peripheral shape of the washer is not particularly limited and may be circular, square, rectangular, or polygonal.

In the present invention, the adhesive for bonding the small flat plate to the inner layer plate is not particularly limited, but it must be able to withstand stress during drilling of reference holes and chemicals and heat during blackening treatment. It is. Among these adhesives, double-sided tape and the like are effective in terms of workability.

The surface to which the washer is bonded must be sandwiched between the washer or the inner layer plate to prevent the eyelet from becoming distorted.

The outer layer silver foil is not necessarily necessary, and the outer layer wiring may be formed by an additive method or the like.

Next, the present invention will be explained using the drawings.

FIG. 1(a) is a sketch of a small circular plate 1 made of metal or resin used in the present invention, FIG. 1(b) is a vertical cross-sectional view of the small flat plate 1, and FIG. 1(C) is a small flat plate. 1 using adhesive 2,
FIG. 3 is a longitudinal cross-sectional view showing a state in which it is adhesively fixed to an inner layer board 3 having a circuit pattern formed on the front and back sides. Then, a reference hole for positioning is drilled from above the small flat plate fixed with adhesive, with the - dotted chain line in FIG. 1(C) as an axis. Next, as shown in FIG. 2, on the inner layer plate 3 to which the washer 1 is bonded,
Layer the inner layer plate 3b (the small flat plate is not glued and the alignment reference holes are drilled only in the inner layer plate) through the prepreg 4, and drive the eyelets 5 into those alignment reference holes to attach the inner layer. 6 Caulk the plates 3, 3b and prepreg 4
Next, as shown in Fig. 3, prepreg 6 is layered on both sides of the set of caulked inner layer plates 3 and 3b (inner layer material), and then outer layer copper foil 7 is layered on both sides of the prepreg 6, which are integrally molded under heat and pressure. A multilayer printed wiring board can be manufactured using this method.

In Figure 3, one of the inner layer boards 3b with a washer and one inner layer board 3b without a washer were caulked together to combine the inner layer materials with four layers of inner layer wiring, but the washer! If two inner layer plates 3 with a washer and one inner layer plate 3b without a washer are caulked with a prepreg interposed between them, an inner layer material having six layers of inner layer wiring can be formed.

(Function) The method for manufacturing a multilayer printed wiring board of the present invention uses a washer in the eyelet method to secure positional accuracy similar to that of a multilayer printed wiring board with six or more layers with workability equivalent to that of a four-layer board. This is what we do.

In other words, by using a washer in the hole-to-eye method, it is possible to suppress the stress deformation of the hollow straight pipe part of the eyelet during heating and pressurizing integral molding, eliminating displacement and denting of the eyelet, and improving positional accuracy. This has become possible.

(Example) Next, the present invention will be specifically explained by examples, Examples 1 and 2. Two sets of two inner layer plates with a thickness of 0.211 nm each having a circuit pattern of 70 μm thick on both the front and back sides. A predetermined small flat plate made of metal or resin was adhesively fixed to the location where the reference hole was to be made in one of the inner layer plates of each set. Next, after drilling a reference hole from the top of the small flat plate, 72 sheets of pre-prep with a thickness of 100 μm were stacked, and then the other inner layer plate with the reference hole drilled was stacked and fastened together using the eyelet method to form the inner layer of Examples 1 and 2. In this case, the thickness of the washer was adjusted to be the same as the thickness after molding two sheets of prepreg. Furthermore, prepreg with a thickness of 100μI was layered on both sides of each inner layer material, and an outer layer of silver foil with a thickness of 18μm was layered on the outside in order, and the whole was heated at 175℃, 4 to 40kQ/C1.
They were integrally molded under heat and pressure for 90 minutes under the conditions of 1' to produce six-layer multilayer printed wiring boards.

Examples 3-4 Prepreg 2 used for the inner layer material in Examples 1-2
The multilayer glint wiring boards of Examples 3 and 4 were all the same as in Examples 1 and 2, except that 74 pre-prened sheets and washers with a thickness corresponding to the height after molding were used instead of 74 sheets. Do not manufacture.

Comparative Example 1 Except for not using a washer in Examples 1 and 2,
A multilayer printed wiring board was manufactured in the same manner as in Examples 1 and 2.

Comparative Example 2 A multilayer printed wiring board was manufactured in the same manner as in Examples 3 to 4, except that the washers used in Examples 3 to 4 were not used.

The multilayer printed wiring boards manufactured in Examples 1 to 4 and Comparative Examples 1 to 2 were tested for misalignment, heat resistance, dimensional stability [dimensional change rate], and workability, and the results were obtained. It is shown in Table 1.

The multilayer printed wiring board of the present invention had excellent mechanical properties, and the effects of the present invention could be confirmed.

Table 1 (Units) The tests for misalignment, heat resistance, and dimensional stability shown in Table 1 were conducted as follows.

Misalignment of the inner layer board: The misalignment of the reference hole dimensions between each inner layer wiring pattern was measured in both the vertical and horizontal directions using a coordinate measuring device.6 Heat resistance: After the multilayer printed wiring board was treated with D-4/100,
After being placed in a soldering bath at 260'C for 30 seconds, the condition of the board (such as measling) was visually observed.

Dimensional stability: Dimensional change rate was measured by MIL method.

In addition, among the items of inner layer misalignment in Table 1, Ll and L2
represent the wiring patterns on the front and back sides of the first inner layer board, respectively, and L3 and L4 represent the wiring patterns on the front and back sides of the second inner layer board, respectively, and the O mark in the front is good and the Δ mark The mark "X" indicates that the product is not good but can be used for practical purposes, and the mark "X" indicates that the product is defective.

[Effects of the Invention] As is clear from the above explanation and Table 1, according to the method for manufacturing a multilayer printed wiring board of the present invention, it is possible to precisely align a plurality of inner layer board patterns, and in particular, the inner layer Effective when the space between the boards is high. Moreover, a multilayer printed wiring board having six or more layers can be manufactured with good workability and at low cost.

[Brief explanation of drawings]

FIG. 1(a) is a sketch of a small flat plate used in the method for manufacturing a multilayer printed wiring board of the present invention, and FIG.
Fig. 1(C) is a vertical cross-sectional view of the small plate in Fig. 1(a).
FIG. 2 is a partial cross-sectional view showing the inner layer material caulked with eyelets. FIG. 4 is a sectional view showing the layer structure of a multilayer printed wiring board separated by the conventional method. FIG. 5 is a partial sectional view illustrating the conventional eyelet method. FIG. 6 is a conventional multilayer printed wiring board. FIG. 3 is a partial cross-sectional view illustrating the distortion of the plate after molding. 1...Small plate (washer), 2...Adhesive, 3
．． 3b, 14...inner layer plate, 4, 6, 15a. 15b... prepreg, 5,17... eyelet,
7゜・Outer M silver leaf.

Claims (1)

[Claims] 1 Multiple inner layer boards with inner layer wiring formed on both the front and back sides,
A method for manufacturing a multilayer printed wiring board comprising a prepreg cured layer and an outer layer wiring, the method comprising: bonding a small flat plate to a reference position of at least one of the plurality of inner layer plates; A drilling step of drilling an alignment reference hole that passes through the inner layer plate and the small flat plate at a reference position of the inner layer plate that has undergone the adhesion process, and a caulking tool in the alignment reference hole of the inner layer plate that has undergone the above drilling process. a caulking process in which the prepreg and other necessary inner layer plates are inserted and caulked, and a molding process in which the prepreg and, if necessary, an outer layer copper foil are laminated and integrally formed on the caulked inner layer plate. A method for manufacturing a multilayer printed wiring board.