JPH0430978B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing an epoxy resin laminate having excellent moldability, drillability, and thermal shock resistance. [Prior Art] Conventionally, bisphenol A type epoxy resins having a relatively low molecular weight and having an epoxy equivalent of 500 or less have been used in the production of epoxy resin laminates. Therefore, during molding, the viscosity is low and the flow is large in the initial stage of heating, making it difficult to maintain plate thickness accuracy. Furthermore, as heating and curing progress, the viscosity rapidly increases and gelation occurs, which narrows the timing of pressurization and makes molding extremely difficult. In addition, the epoxy resin laminates manufactured using this method cannot absorb the impact of high-speed drill rotation during the drilling process, which is essential in the production of printed circuit boards, resulting in cracks and roughness on the inner surface of the drill holes. I felt relaxed. Furthermore, when sudden temperature changes are applied such as in the solder coating process, the epoxy resin cannot follow the expansion and contraction caused by the sudden temperature change, and breaks down at the interface between the metal foil on the surface and the glass fiber inside. It happened. In this way, in laminates manufactured using low-molecular-weight epoxy resins, the molecular weight between crosslinking points is small, so the degree of freedom in the movement of molecular chains is small, and it is susceptible to mechanical shock during drilling and thermal impact during solder coating. There were problems in terms of reliability, as the impact could not be absorbed as kinetic energy of the molecular chains, leading to destruction of the resin. [Objective of the Invention] The present invention solves the above-mentioned difficulties in press molding, laminate drilling workability, and destruction during thermal shock, and provides a highly productive and reliable laminate for printed circuit boards. With the goal. [Structure of the Invention] The present invention comprises laminating prepregs prepared from a varnish whose main components are a brominated bisphenol A epoxy resin having an epoxy equivalent of 700 to 1200 and a bisphenol A novolak epoxy resin as the epoxy resin component. , a method for producing an epoxy resin laminate, characterized by heat-pressing molding. The bisphenol A type epoxy resin used in the present invention is a brominated type having an epoxy equivalent of 700 to 120. The bromine content is preferably 15 to 30%. As mentioned above, laminates made of low-molecular-weight epoxy resins are unable to absorb mechanical and thermal shocks during the processing process, often leading to breakage. Therefore, if the epoxy resin used is a brominated type and its molecular weight is increased to have an epoxy equivalent of 700 or more, the molecular weight between the cross-linking points will be larger than before, which will cause the mechanical and thermal shock during processing mentioned above. It was found that the laminate is absorbed as molecular motion, making it difficult for cracks and other damage to occur in the laminate. On the other hand, when the molecular weight of bisphenol A type epoxy resin is increased, the viscosity does not decrease even when heated during pressure molding, and the resin does not penetrate into the interface with glass fibers or metal foil, leaving bubbles and reducing adhesive strength. let Furthermore, since the molecular weight between the crosslinking points becomes too large,
Swelling due to solvent occurs and solvent resistance decreases. Therefore, the decrease in crosslinking density due to increase in molecular weight can be compensated for by using a novolak type epoxy resin in combination. It has been found that when this novolac type epoxy resin is used in combination, a brominated bisphenol A type epoxy resin having an epoxy equivalent of 1200 or less can be used. If a resin with a higher weight than this is used, even if a novolak type epoxy resin is used in combination, it will not be possible to obtain a product that can withstand practical use in terms of solvent resistance and the like. In the present invention, a bisphenol A novolak type epoxy resin is used as the novolak type epoxy resin. The bisphenol A novolac type epoxy resin has the following structure. The use of bisphenol A novolac type epoxy resins provides increased flexibility and less distortion during curing compared to the use of regular phenol or cresol novolac type epoxy resins, making molding easier. The resulting laminate has excellent properties such as dimensional stability, thermal shock resistance, and drillability. The bisphenol A novolac type epoxy resin preferably has a molecular weight of 450 to 1,400 from the viewpoint of the above characteristics. In addition, the blending ratio with bisphenol A type epoxy resin is not particularly limited, but
Bisphenol A novolak type epoxy resin for 60 to 90 parts (parts by weight, same below) of type epoxy resin
40 to 10 parts is preferred. In the present invention, even if a part of the brominated bisphenol A type epoxy resin having an epoxy equivalent of 700 to 1200 is replaced with an epoxy compound having a lower epoxy equivalent, the moldability, drilling workability, and thermal Since an effective improvement in impact properties is observed, this case is also included in the present invention. [Effects of the Invention] According to the method of the present invention, there is a wide range of selection of pressurizing conditions, and moldability is greatly improved compared to the conventional method. Furthermore, the resulting epoxy resin laminate has extremely little warpage or dimensional change due to heat treatment, the inner surface of the drill hole is neatly processed during drilling, there is also little wear on the drill blade, and the resin is resistant to thermal shock during solder coating. This improves peeling at the interface between metal foil and glass fiber and cracks in the resin, making it possible to supply epoxy resin laminates for printed circuit boards that are highly reliable and easily produced. [Example] Examples will be described below in more detail. After impregnating glass cloth with epoxy resin varnish having the resin formulations of Examples 1 to 4 shown in Table 1 and drying it, 8 sheets of this prepreg (resin content 46% by weight) and copper foil were heated and heated in a press. Thickness by pressing
A 1.6 mm epoxy resin laminate was obtained. Table 2 shows the characteristics evaluation results of the obtained laminate. [Comparative Examples] Comparative Examples 1 (conventional) and 2 to 4 shown in Table 3
An epoxy resin laminate was obtained from an epoxy resin varnish having the resin formulation in the same manner as in the examples. The results of this characteristic evaluation are shown in Table 4. It can be seen that the epoxy resin laminate obtained by the method of the present invention not only has excellent thermal shock resistance and drill workability, but also has good general properties and excellent practical properties.

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Claims (1)

[Claims] 1 As an epoxy resin component, epoxy equivalent is 700
An epoxy resin laminate characterized by laminating prepregs prepared from a varnish containing a brominated bisphenol A type epoxy resin having a molecular weight of 0 to 1200 and a varnish containing a bisphenol A novolac type epoxy resin as the main components, and then molding under heat and pressure. manufacturing method.