JPS6231513B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a single-sided metal foil-clad laminate with improved warping and twisting. As is well known, a metal foil-clad laminate is manufactured by laminating a predetermined number of prepregs impregnated with a resin varnish and then dried, placing a metal foil on the surface, and heating and pressurizing the prepreg. Demand for this laminate as a printed wiring board has increased in recent years. However, in single-sided metal foil-clad laminates, the thermal expansion coefficients of the metal foil and the resin base material are significantly different, so large warps and twists occur during the etching process and molten solder (230-260°C) immersion process. It has been difficult to automate the assembly of these twisted parts into a device. As a result of detailed research to solve this problem, the present inventors found that when laminating prepregs made by impregnating the base material with resin varnish and drying it, the side on which the metal foil is placed and the side on which the metal foil is not placed are separated. One-sided metal foil-clad laminates are produced by laminating prepregs with different properties on the surface, heating and pressing them, and then undergoing an etching process.
It was discovered that both warping and twisting can be suppressed during the soldering process. Generally, it is assumed that the warping or twisting of a laminate is due to residual stress within the laminate after forming. Therefore, as a means to suppress warping and twisting of the laminate, methods such as lowering the molding pressure and reducing the twisting of the glass fiber cloth that is the base material have been used. However, even if such measures are employed, residual stress in the laminate cannot be completely eliminated. Furthermore, in a single-sided metal foil-clad laminate, the coefficient of thermal expansion of the metal foil and the coefficient of thermal expansion of the resin and base material are significantly different, so even if the residual stress in the laminate is reduced, warping and twisting cannot be eliminated. Therefore, in the present invention, although residual stress is generated in a minute portion inside the laminate, the residual stress generated due to the difference between the thermal expansion of the metal foil and the thermal expansion of the resin and base material is transferred to the entire single-sided metal foil-clad laminate. The properties of the prepreg base material on both surfaces were varied in order to cancel out the residual stress. That is, the gelation time of the resin of the prepreg on the surface 1 on which the metal foil is placed is the surface 1 on the side where the metal foil is not placed.
It is characterized by having a gelation time shorter than that of the resin of the prepreg sheet. If this configuration is reversed, a large amount of warping will occur, with the metal foil being on the inside.
Note that the resin and base material used for both surfaces may be the same or different. The resin used in the present invention is a general thermosetting resin such as an epoxy resin or a phenolic resin, and a heat-resistant thermoplastic resin such as polysulfone, polyphenylene oxide, or polyimide is also used for the inner layer. In the present invention, copper foil is used as the metal foil, and the difference in the gelation time of the prepreg resin (on a 160℃ heating plate) between the side on which the copper foil is placed and the side on which the copper foil is not placed is 30
It is appropriate that the time be within the range of ~300 seconds. The difference is 300
If the difference exceeds 30 seconds, a large warpage occurs in the etching process or molten solder dipping process, with the copper foil facing outward, and if the difference is 30 seconds or less, no improvement in prevention of warpage or twisting was observed. In the present invention, the gelation time is measured by collecting 0.2g of the resin powder rubbed off from the prepreg and
The resin is melted while stirring on a hot plate at 160°C, and the time taken until the resin stops stringing while being stirred is measured. In this way, in the present invention, the gelation time of the prepreg resin is different, and this difference is
It can be attached by using different resins on both surfaces. Further, even if the same type of resin is used, when the resin is cured to the B stage in the prepreg manufacturing stage, the gelation time can be varied by adjusting the degree of curing progress. Next, embodiments of the present invention will be described. Example: Polysulfone resin was impregnated with tricrene as a solvent to a resin content of 60% by weight, and heated at 140°C.
Nine sheets of glass nonwoven fabric prepreg obtained by drying are layered, and epoxy resin is applied to both surfaces to increase the resin content.
Glass woven prepreg impregnated to a concentration of 35% by weight and dried was layered one by one. Glass woven prepreg was prepared by adjusting the gelation time of the resin on a 160℃ heating plate for 3 minutes on the side where the copper foil is placed, and the same 5 minutes on the side where the copper foil is not placed. ^cm3
A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained by heating and pressing for 30 minutes. (Product of the present invention). Conventional example: 160 on both surfaces, the side where copper foil is placed and the side where it is not placed.
A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained (conventional product) using a glass nonwoven fabric prepreg with a resin content of 35% by weight and a gelation time of 4 minutes on a heating plate at ℃, and otherwise in the same manner as in the example. . Table 1 shows the characteristics of the product of the present invention and the conventional product. The size of the sample is 300 x 300 mm, and the residual copper ratio is 40%.

[Table] * Positive warping = Curving with the copper foil on the outside Negative warping = Curving with the copper foil on the inside As is clear from Table 1, according to the present invention, by changing the gelling time, the metal foil can be mounted. The curing time of the prepreg on the side to be placed is faster than the hardening time of the prepreg on the side to be placed, which improves the balance of residual stress in the formed laminate, and prevents warping of the laminate due to residual stress after forming. However, the opposite stress can be applied during the etching process and molten solder dipping process to flatten the laminate. In addition, even if the gelation time of the resin of one sheet of prepreg on the surface on which the metal foil is placed is shortened, a laminate containing voids will not be formed, and its industrial value is extremely large. be.

Claims (1)

[Claims] 1 When stacking an appropriate number of prepregs obtained by impregnating a base material with resin varnish and drying them and placing copper foil on one side for lamination molding, the resin of one prepreg on the side on which the copper foil is placed is A single-sided metal foil-clad laminate characterized in that the gelation time is 30 to 300 seconds (measured on a 160°C heating plate) shorter than the gelation time of the resin of one sheet of prepreg on the non-mounted surface. manufacturing method.