JPS62128596A - Manufacture of rigid multilayer printed circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a printed circuit board on which electronic components are mounted, and in particular to a rigid multilayer printed circuit board that is highly economical and enables high-density surface mounting. Relating to a manufacturing method.

(Prior art) Conventionally, printed circuit boards have been made by firmly adhering Cu foil to a paper phenol or glass epoxy board and etching it to form a predetermined circuit, or by laminating these in multiple layers. A high-density product is used. Printed circuit boards like the one mentioned above have the advantage of being relatively economical because they can be mass-produced; For this reason, circuit boards mounted with components using high-density double-sided mounting often reach the permissible limits in terms of thermal management. This is a problem that requires an urgent solution in electrical circuits, original circuits, and power electronics circuits. In other words, as electronic components become more compact and denser, and at the same time shift to surface-mounted types, it can be said that the problem of heat dissipation of the board is of universal importance (the problem that the invention aims to solve). ) As a countermeasure to the above-mentioned problem, a printed circuit board whose substrate is made of ceramic such as alumina, which has high heat conductivity, is used. However, such ceramic circuit boards have a 2 to 3
There are problems in that the manufacturing cost is doubled and a special manufacturing process is required. Also, in the case of ceramic circuit boards,
Dimensional changes occur during heating and firing, and there is no way to avoid deformation at that time, so there are significant restrictions on the shape of the substrate.

Therefore, Cu foil' = M (J L
Two types of circuit boards have been developed, including etching and printing. However, in the case of this type of printed circuit board, since it is printed on one side, there remains the problem that high Tf degree mounting cannot be fully achieved.

The present invention has been made in view of these points, and is a rigid multilayer print that improves heat transfer characteristics, enables high-density A-mounting, and enables mass production to reduce manufacturing costs. A method for manufacturing a circuit board is provided.

(Means for Solving the Problems) The method of the present invention will be explained based on the drawings, taking a two-way circuit board as an example.

Figure 1 (ai shows the flexible conductor of the starting material, 1 is made of polyimide, polyamide, polyether, etc.)
4 Heat-resistant plastic foil, thickness 25-100μm
That's about it. 2a and 2b are metal conductor foils such as Cu foil,
Generally, those having a thickness of 35 μm, 18 μm, 12 μm, etc. are used. The plastic 1 and the metal conductor foil 2 may be joined using an adhesive or directly by thermocompression bonding. Here, "flexible" means the flexibility of the material resulting from the use of a 4u' plastic body, and the use of this thin plastic foil body is an essential condition for the heat dissipation of the circuit board, as will be described later.

The first [9fbl] shows a state in which a through hole 3 is formed by drilling or punching. Next, Figure 1 f
As in cl, the surface of the plastic 1 is activated with a Pd catalyst using a conventional method, and then made conductive by Cu chemical plating.
Subsequently, a Cu plating layer 4 of a desired thickness is formed by electroplating.

Next, a mask layer is formed using Eratin Breath I- or a photosensitive dry film by a conventional method, and then etching is performed to form the first layer circuits 5a and 5b on one side.

Pattern 5C. FIG. 1 (dl shows the state after mask row peeling).

Next, the flexible conductor that has gone through the above steps is bonded to the metal substrate 7 via the insulated IW 86 which also functions as an adhesive. The metal substrate 7 includes a Cu plate, an AI plate, or an F plate.
An e-board or the like may be used, and one that has been previously subjected to insulation treatment may also be used. FIG. 1 te+ shows this situation.

After that, as shown in FIG. 1 if), the second fV1 circuit 8a,
8b is formed in the same manner as in the first layer circuit of IYII.

The second layer layers 98a and 8b are coated with solder resist, flux, and (as necessary, Au, Ag, Sn, and Sn).
- Finished with plating such as PB.

The above operations are basically the same as those for ordinary printed circuit boards. Moreover, although the panel plating method was employed as described above to form the Cu plating layer 4, it goes without saying that the circuit can also be efficiently formed by a pattern plating method, a partially additive method, or the like.

Furthermore, in multilayer circuits with three or more layers, flexible conductors with circuits formed on both sides except for the outermost layer are laminated, through holes are formed, and then bonded to a metal substrate. A method is adopted to do so.

(Function) Wood inventor (well, he has already filed a patent application in 1986-217 for red type multilayer printed circuit boards using flexible conductors).
This is proposed in No. 3, and is related to improvements in the manufacturing method for FIJJ+. .

2.5 To explain the circuit board, the second flower circuit 8a,
The metal conductor foil 2b to be processed as 8b remains unprocessed,
In order to enter the bonding process with the metal substrate 7, the mold conductor foil 2b acts as a reinforcement and withstands the pressure of pressing etc., and the through holes 3 and the thin first layer circuits 5a, 5b, 5.
The lamination process can be completed without any adverse effects. That is, the plastic 1 tends to stretch due to the pressure and heat during the bonding process, especially the through hole 3.
The metal conductor foil 2b is effective as a reinforcing material to prevent cracks from forming at the edges.
I'm angry.

Here, since the thickness of the plastic 1 is as thin as possible from the standpoint of heat dissipation, the thickness of the metal conductor i2b can also sufficiently suppress the deformation.

Furthermore, since the circuit board obtained by the method of the present invention allows components to be mounted on at least one side of the metal substrate, it has high conductivity A even in 1:'S density electronic circuits. Has heat dissipation properties, ri! J road (:″,
Great reliability [! ``Improved to Zurokoto Tesaro.''

(Actual IJI example) Below, an example of the present invention will be explained.

25 μm thick foil with a thickness of 3 on both sides
A flexinople conductor was obtained by pasting a 5 μm electrolytic Cu layer.

Various through holes with hole diameters of 0.5 to 2 mmφ were punched into the ice crystals.Next, the ice crystals were washed, washed with water, and then soaked in a 1% Pd (12% HC1' aqueous solution). Soak,
Next, the plate was plated to a thickness of about 0.5 μm by immersing it in a CU't Mesimo bath of ENBREY 1-CU 40 G (manufactured by XYAPAN METAL FINISHING Co., Ltd.) at 60°C for 20 minutes. , further Cu 5o4120 g,/e,
H2So430g/l, I・y Plutina (!!!
No Pharmaceutical Co., Ltd. fM) 5ppm Cu5O, i valley (30℃,
The entire surface was electroplated with Cu having a thickness of 8 μm (5 A/dm').

Next, one side of the ice crystal was coated with a photosensitive dry film (DFR).

Asahi Kasei Co., Ltd.) was pressure-bonded, exposed and developed, and then etched and soothed with FeCl3 solution to form a first layer circuit. After peeling off the dry film, the ice crystals were removed from an alumite-treated AI plate (450mm x 450mnIX), 2m long.
Press bonding was performed using an epoxy adhesive containing 15% BN in mtl (160°C, 15 kg/c+d.

0.5hr).

Subsequently, the same process as for the first layer circuit was performed on the non-circuit surface of the ice crystal to form a second layer circuit.

Thereafter, a solder resist (HR16, manufactured by Taiyo Ink Co., Ltd.) and flux were applied to the parts of the ice crystal except for the component mounting pads for finishing.

No breakage failures were observed in the ice crystals at the initial stage, and no cracks were observed when some circuits were cut and examined under a microscope. Furthermore, 5 cycles of alternate immersion using 250°C oil and cold water were performed.
Although the test was repeated 0 times, the change in electrical resistance remained within 5% of the initial value. For comparison, a circuit board on which the first and second layer circuits had been formed and then laminated onto an A4 board was subjected to the same alternating dipping as described above, and the change in electrical resistance was 10% of the initial value after 10 times. %, and after 50 times, a break occurred in a part of the 1st line. Many failures such as disconnections were observed near the 0.3m+h line and through-holes.

It is extremely easy to produce a circuit board using the method of the present invention, and the resulting circuit board has excellent heat dissipation properties,
It was experimentally confirmed that the heat transfer properties are excellent. In addition, it was found that the packaging density was comparable to that of conventional ceramic substrates, and that the manufacturing cost (manufacturing cost) could be reduced by about 50%.

(Effects of the Invention) The present invention improves the heat dissipation and heat transfer characteristics of a multilayer printed circuit board by using a metal substrate and a plastic foil body, and also enables highly reliable and high-density surface mounting. It has become! The M manufacturing process facilitates mass production and reduces manufacturing costs.

[Brief explanation of drawings]

FIGS. 1(8) to 1(f) are cross-sectional views illustrating the present invention step by step. Dobrastic, 2a, 2b・Metal conductor foil, 3 Through hole, 4-Cu1 so'f layer, 5a, 5b. 5c 1st layer circuit, 6 Insulating layer, 7 Metal substrate, 8a
, 8b 21st layer circuit. No. 1 C OJ) ~--- 9 5 g Procedural amendment (voluntary) October 20, 1985

Claims (2)

[Claims] (1) When manufacturing a rigid multilayer printed circuit board, a) a step of forming desired through holes in a flexible conductor obtained by pasting metal conductor foil on both sides of a plastic foil body, and b) the step of forming the through hole a step of forming a Cu plating layer on the entire surface of the flexible conductor including inside the hole, c) forming a first layer circuit on one side of the flexible conductor, and d) using the first layer circuit formation surface as a bonding surface, A rigid multilayer print characterized by sequentially performing the steps of: bonding the flexible conductor and the metal substrate via an insulating layer; and e) forming a second layer circuit on the non-bonding surface of the flexible conductor. Method of manufacturing circuit boards. (2) The rigid type according to item 1, characterized in that the laminated circuit is formed leaving the outermost layer, and then this is bonded to a metal plate via an insulating layer, and then the outermost layer circuit is formed. A method of manufacturing a multilayer printed circuit board.