JPS6345896A - Manufactue of multilayer printed interconnection board - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] C. Purpose of the Invention (Industrial Field of Application) The present invention provides a method for processing small-diameter drill holes with a smooth copper foil surface, less shaft runout of the drill, and good drill smear and inner wall roughness. The present invention relates to a method for manufacturing a multilayer printed 4Q board.

(Prior art) In the field of industrial electronics, the density of wiring is rapidly increasing, and with the recent improvement in the degree of integration of LSIs, the packaging has changed from the conventional dual-in-line package to a multi-terminal package. The wiring density has also become extremely high. Print layout I for mounting this flat back type package! Unlike conventional printed wiring boards for mounting dual-in-line packages, there is no need to insert component leads into through-holes on the board, so you can place them by using small-diameter through-holes! Efforts are being made to increase the density ff.

The small-diameter drilling required to create small-diameter through holes requires drilling with good drill smear and inner wall roughness. In the conventional 7628 type 2 board with a multilayer printed layout in which a thick glass cloth is placed directly below the copper foil, the surface of the copper foil is rough, causing the drill shaft to run out, causing problems such as drill smear and inner wall roughness. . In order to solve this problem, attempts were made to smooth the copper foil surface and improve drilling workability by placing one or more thin glass cloths with a thickness of 0.11II11 or less in contact with the copper foil. There is a way. However, the glass cloth used in this method with a thickness of 0.1111 or less is 7628 mm thick.
It is more expensive than other types of glass cloth, and the surface of the tA foil cannot be sufficiently smoothed, and conversely, the glass cloth's grains become uneven, which can cause shaft wobbling of the drill, etc. Another idea was to use adhesive-coated copper foil to improve the surface of the copper foil, but the adhesive increases the resin content, which increases the frequency of smearing and increases the cost of the copper foil. There was a drawback.

(Problems to be Solved by the Invention) The present invention was made in order to eliminate the above-mentioned drawbacks. It is an object of the present invention to provide a multilayer printed wiring board with less drill shaft runout and drill smear during small-diameter drilling, and with good inner wall roughness.

[Structure of the Invention] (Means and Effects for Solving the Problems) As a result of intensive research to achieve the above object, the present inventor has developed a method of forming a copper foil with a constant thickness that has a cushioning effect on the surface of the copper foil. We have discovered that by arranging a thermoplastic film, we can provide a multilayer printed wiring board with a smooth copper foil surface, no drill shaft runout or drill smear, and good inner wall roughness, and at a low cost, and have completed the present invention. be.

That is, the present invention provides a method for manufacturing a multilayer printed wiring board in which prepreg and copper foil are laminated on both sides of an inner layer board to form a heat-pressure laminate. This is a method for producing a multilayer printed wiring board characterized by further arranging a thermoplastic film having a thickness of 50 to 150 μm on the copper foil surface. It is desirable that the thermoplastic film has a melting temperature of 100 to 150°C.

The inner layer plate used in the present invention may be one of two or more layers that are normally used, and may be made of materials that are used (circuit materials,
There are no particular restrictions on the resin, base material) or manufacturing method, and any inner layer plate can be used.

The prepreg used in the present invention may be one made by impregnating glass cloth with a thermosetting resin and drying the coating. The glass cloth used here has a thickness of 1
Although the effect of the present invention can be achieved even if the glass cloth is thin with a thickness of 00 μm or less, thick glass cloth with a thickness exceeding 100 μm, such as 762
The effect is remarkable in the case of type 8 (thickness: 180 μm). Examples of the thermosetting resin to be used include epoxy resins, polyimide resins, and modified resins thereof, which may be used alone or in combination for at least 2 seconds.

The copper foil used in the present invention is not particularly limited and may be of any type, but from the viewpoint of cost and appearance, it should not be too thick (
, and preferably one without adhesive.

The thermoplastic film used in the present invention may be one that satisfies the following conditions. The first is that the thickness is within the range of 50 to 150 μm.
If the thickness is less than 50 μm, the cushioning properties will not be effective and the appearance will not be finished smoothly, which is not preferable. Also 150μ
If it exceeds m, the cushioning properties will be good and the appearance will be smooth, but the cost will increase, which is not preferable. Preferably, the thickness is 80 to 120 μm from the viewpoint of cushioning properties and cost.

Second, the melting temperature is within the range of 100 to 150°C. If m11 is less than 100°C, the molded product may slip during molding, making molding dangerous and undesirable. Moreover, if the temperature exceeds 150°C, the desired effect cannot be obtained, which is not preferable.

Therefore, the temperature is most preferably 120 to 140°C.

Any thermoplastic film may be used as long as it satisfies these two conditions. Specifically, a biaxially stretched oPP film (polypropylene film) or the like can be preferably used.

Thickness is 50-150μm and melting temperature is 100-150℃
By using a thermoplastic film, a cushion effect is created, and pressure is applied without being applied directly to the copper foil.
The surface of the copper foil is smoothed.

This method of manufacturing a multilayer printed wiring board can be carried out extremely easily by simply placing a thermoplastic film between the fA foil surface and the stainless steel plate in addition to the usual manufacturing method.

(Example) Next, the present invention will be specifically explained with reference to Examples.

Example 1 A circuit was formed using 70 μm tA foil on a 0.4A+E glue material, and 76
28 type glass cloth impregnated with flame retardant epoxy resin, thickness 0.21 with resin adhesion amount 40-45% by weight
Lay three sheets of prepreg of 1IIl each, layer 18μm thick copper foil on the top and bottom surfaces, and then layer 50μm thick copper foil on the top and bottom surfaces.
A 4-layer printed wiring board was manufactured by disposing a micrometer OPP film, sandwiching it between stainless steel plates, and integrally molding the film by heating and pressing.

Example 2 A four-layer printed wiring board was manufactured in the same manner as in Example 1 except that a 100 μm thick OPP film was used instead of the 50 μm thick OPP film in Example 1.

Comparative Example 1 A 4-layer printed wiring board was fabricated in the same manner as in Example 1 except that the 550 μm thick OPP film was not used.

Comparative Example 2 In Comparative Example 1, an inner layer board base material with a thickness of 0.5 μm was used instead of the inner layer board base material with a thickness of 0.4 mm, and 83 sheets of prepreg each using 7628 type glass cloth were used. All comparative examples except that instead of 62 sheets of prepreg using 7628 type glass cloth, and 1 sheet each of prepreg using 216 type glass cloth with a thickness of 0.1 mm above and below were prepared. A 4-layer printed wiring board was manufactured using wIJ in the same manner as 1.

Comparative Example 3 All comparisons were made except that instead of the 18 μm thick copper foil in Comparative Example 1, an 18 μm thick adhesive-coated copper foil coated with 30 g/m2 of the same resin impregnated into the prepreg was used. A four-layer printed wiring board was manufactured in the same manner as in Example 1.

The four-layer printed wiring boards manufactured by TJ in Examples 1 to 2 and Comparative Examples 1 to 3 were evaluated in terms of appearance, drill shaft runout, inner wall roughness, drill smear, etc., and the results are shown in Table 1. In all cases, remarkable effects of the present invention were observed.

Table 1 *1: O...Good, ○...Good, Mouth...Slightly good, Δ
...Slightly poor, ×...Poor.

[Effects of the Invention] As is clear from the above explanation and Table 1, the method for producing a multilayer printed wiring board of the present invention has the advantage that by using a thermoplastic film of a predetermined thickness, the surface of the copper foil becomes smooth;
The h-method is industrially useful because it can provide a multilayer printed wiring board with less axial runout of the drill during drilling, no drill smear, good inner wall roughness, and an inexpensive overall balance.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a multilayer printed wiring board in which a prepreg and a copper foil are superimposed on both sides of an inner layer board to form a heat-pressure laminated body, further comprising a layer having a thickness of 50 to 150 μm on the copper foil surface. A method for manufacturing a multilayer printed wiring board characterized by arranging a thermoplastic film. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the thermoplastic film has a melting temperature of 100 to 150°C.