JPH0341064B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention involves impregnating a cellulose fiber base material and an aluminum hydroxide mixed cellulose fiber base material with a thermosetting resin such as a phenol resin, an epoxy resin, an unsaturated polyester resin, etc., and then drying it to form a prepreg. A thermosetting resin with good punching workability, which is formed by laminating under heat and pressure, with the surface layer being a cellulose fiber base prepreg and the middle layer being an aluminum hydroxide mixed cellulose fiber base prepreg. This relates to laminates. With the recent development of electronic devices, the printed wiring circuit boards used in electronic devices are becoming more densely wired, while the mounting of components is also becoming easier with automated component insertion, surface mounting, and soldering using flow solder. Rationalization of production is progressing. Under such circumstances,
The requirements for copper-clad laminates include excellent punching workability, dimensional stability, and electrical properties.In particular, when looking at punching workability, the wall surface of the punched hole should be straight and smooth when viewed from the cross section. It is hoped that Conventional laminates include phenolic resin laminates, epoxy resin laminates, unsaturated polyester resin laminates, etc. that are based on cellulose fiber paper such as kraft paper and linter paper. However, these laminates are still not satisfactory in terms of punching workability, especially the straightness and dimensional stability of the wall surface of the punched holes, and trouble-free automatic loading and surface mounting of parts, uniform soldering performance, etc. It is a characteristic that is strongly desired to be improved in terms of (uniform soldering) and through-hole connection reliability. In the present invention, a cellulose fiber base material prepreg is arranged in the surface layer and a cellulose fiber base material prepreg mixed with aluminum hydroxide is arranged in the middle layer, and the composite laminate has excellent punching workability, and It was discovered that the dimensional stability in the thickness direction and electrical properties are also good. In other words, it has excellent punching workability, and in particular, the straight and smooth hole wall means that the lead wire will not get caught during automatic insertion of parts, allowing trouble-free insertion, and that the inserted lead wire and Since the gap between the hole and the hole wall is constant, it is possible to apply the solder uniformly, which reduces the time required to repair defective soldering after parts are mounted, which is a great advantage in terms of production. The excellent dimensional stability in the direction and thickness direction means that this laminate is suitable for automatic insertion and surface mounting printed wiring circuit substrates that require positional accuracy in the surface direction, as well as for printed wiring circuit substrates that require dimensional changes in the thickness direction. This shows that it is suitable for printed resistor substrates having silver through-holes and other parts that require small size, as well as general mesh through-hole substrates. To explain the present invention in more detail, the cellulose fiber base material used is generally a base paper for laminated boards made using kraft pulp fibers or linter pulp fibers. As the aluminum hydroxide mixed cellulose fiber base material, a material obtained by mixing cellulose fibers such as kraft pulp fibers and linter pulp fibers with aluminum hydroxide powder alone or together with glass fibers is used. The type of aluminum hydroxide powder to be mixed is not particularly limited, but it is preferably one with a gibbsite crystal structure that has a high thermal decomposition temperature, and the average particle size is preferably 50 μm or less, more preferably 20 μm or less. Heat-resistant gibbsite crystals are preferred as aluminum hydroxide because they require resistance to the heat received during the processing of laminates, especially during soldering, and the grain size is 50 μm.
It is preferable to avoid the above because the water resistance and electrical properties deteriorate. The amount of paper mixed is not particularly limited, but a preferable range is 30 to 85%. If it is less than 30%, the dimensional stability, straightness and smoothness of the wall of the punched hole will be poor, and if it is more than 85%, the strength of the prepreg will be weak during impregnation and drying with thermosetting resin varnish, and workability will be poor. Aluminum hydroxide, which is a mixed material, is preferable because of the transparency of the laminate and the ease with which it can impart heat resistance.
Dimensional stability can be further increased by mixing a small amount of glass fiber with a diameter of ~3 μm and a length of 3 to 20 mm. A sufficient effect is exhibited at a paper mixing ratio of 2 to 20%. As thermosetting resins, phenolic resins,
Examples include epoxy resins and unsaturated polyester resins, and coupling agents, pigments, dyes, inorganic fillers, etc. can be mixed into these resins. Prepreg can be obtained by the usual method, but in this case, the cellulose fiber base material and the aluminum hydroxide-mixed cellulose fiber base material may be pretreated with water-soluble low-molecular-weight phenol resin, methylol melamine resin, etc. Effective. The cellulose fiber base material prepreg thus obtained and the aluminum hydroxide mixed cellulose fiber base material prepreg were arranged to form a surface layer and an intermediate layer, respectively, and the laminate obtained by heating and pressing was processed by punching. It has excellent properties, dimensional stability in the plane direction and thickness direction, and good electrical properties, making it highly useful. Punching workability, especially straight and smooth hole walls, is important in the punching process, at the initial stage when the die pin descends and contacts the laminate and begins shearing, and at the initial stage when the pin begins to bite into the laminate. In this laminate, the shear surface is During the formation and growth stage, the shear stress received from the pin and die is concentrated at the interface between the aluminum hydroxide fine particles and the thermosetting resin, thereby reducing the deviation of the maximum stress line from the pin side and the die side. It is thought that the wall surface of the punched hole becomes a smooth linear shape because the penetrating portion becomes very small due to the breakage. On the other hand, if a laminate is made only from aluminum hydroxide-mixed cellulose fiber prepreg, it will not be of practical use because surface cracks will occur during punching and the soldering heat resistance will be poor. By disposing a cellulose fiber base material in the surface layer, a practical laminate with excellent punching workability, dimensional stability in the plane direction and thickness direction, and good electrical properties can be obtained. This will be explained below using examples. Example 1 Kraft paper was impregnated with a phenolic resin content of 44% and dried prepreg was used as the surface layer, while aluminum hydroxide mixed kraft paper (mixed paper ratio aluminum hydroxide/kraft = 80/20) was impregnated with phenol. Impregnated and dried prepreg with a resin content of 39% is placed in the middle layer, and a 35μ electrolytic copper foil is combined on one side of the prepreg, and 90% is heated at 170℃ and 80Kg/ ^cm2.
A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained by heat-pressure lamination molding for 1 minute. Its properties are shown in Table 1, and it shows that it has excellent punching workability, and in particular, the shrinkage of the punched hole is very small and a linear hole wall shape is obtained.
Furthermore, it was an excellent laminate with excellent dimensional stability, soldering heat resistance, and insulation resistance. Example 2 Kraft paper was impregnated with a phenol resin content of 44% and a dried prepreg was used as the surface layer, while aluminum hydroxide mixed kraft paper (mixed paper ratio aluminum hydroxide/glass fiber/kraft =
77/3/20), impregnated and dried prepreg with a phenolic resin content of 41% was placed in the middle layer,
A 35 μm electrolytic copper foil was combined on one side and heat-pressure lamination molding was performed under the same conditions as in Example 1 to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Its properties are shown in Table 1, and it shows that it has excellent punching workability, particularly the amount of punching shrinkage is very small, and a linear hole wall shape is obtained. Furthermore, it was an excellent laminate with excellent dimensional stability, soldering heat resistance, and insulation resistance. Example 3 Linter paper was impregnated with a phenolic resin content of 46% and dried prepreg was used as the surface layer, while aluminum hydroxide mixed kraft paper (mixed paper ratio aluminum hydroxide/kraft = 40/60) was impregnated with phenol. An impregnated and dried prepreg with a resin content of 44% was placed in the middle layer, a 35μ electrolytic copper foil was combined on one side, and heat and pressure lamination molding was performed under the same conditions as in Example 1 to form a board. A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained. Its characteristics are shown in Table 1,
It has excellent punching workability, particularly the shrinkage of the punched hole is very small, and a straight hole wall shape is obtained. Furthermore, it was an excellent laminate with excellent dimensional stability, soldering heat resistance, and insulation resistance. Example 4 Kraft paper was impregnated with 45% epoxy resin and dried prepreg was used as the surface layer.
Aluminum hydroxide mixed kraft paper (mix ratio aluminum hydroxide/kraft = 40/60) is impregnated with 44% epoxy resin, and a dried prepreg is placed in the middle layer, and 35μ electrolytic copper foil is placed on one side of the prepreg. The combination was heated and pressed for 90 minutes at 170° C. and 50 kg/cm ² to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Its properties are shown in Table 1, and it has excellent punching workability, especially the shrinkage of the punched hole is very small.
A linear pore wall shape is obtained. Furthermore, it was an excellent laminate with excellent dimensional stability, soldering heat resistance, and insulation resistance. Comparative Example 1 The kraft paper prepreg used in Example 1 was combined alone with 35μ electrolytic copper foil, and heat-pressure lamination molding was performed under the same conditions as Example 1 to obtain a sheet with a thickness of 1.6 mm.
A single-sided copper-clad laminate was obtained. The characteristics are shown in Table 1, and it can be seen that the dimensional stability and punching workability were inferior to those of the examples, and in particular, the punched hole shrinkage was large and a straight hole wall shape was not obtained. Comparative Example 2 The linter paper prepreg used in Example 3 was combined alone with 35μ electrolytic copper foil, and heat-pressure lamination molding was performed under the same conditions as Example 1, resulting in a plate thickness of 1.6 mm.
A single-sided copper-clad laminate was obtained. The characteristics are shown in Table 1, and it can be seen that the dimensional stability and punching workability were inferior to those of the examples, and in particular, the punched hole shrinkage was large and a straight hole wall shape was not obtained. Comparative Example 3 The aluminum hydroxide mixed kraft paper used in Example 1 was combined alone with 35μ electrolytic copper foil,
Heat and pressure lamination molding was performed under the same conditions as in Example 1 to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Its properties are shown in Table 1, but cracks occurred during punching and the soldering heat resistance was poor, making it unsuitable for practical use.

【table】

[Table] The test method is as follows. (1) Punching workability (i) Surface, end face, hole: According to ASTM D-617 (Punching temperature: 60℃) (ii) Punching hole shrinkage: Punching at 60℃ using a die with pin diameter of 1.0mm and one side clearance of 0.10mm The punched hole a-
The value of b was taken as the amount of shrinkage of the punched hole ((1) Laminated board,
(2) copper foil). (2) Dimensional stability (heat shrinkage rate) Shown as the rate of change with respect to the initial dimension after constant heating and cooling treatment from room temperature to 250°C at a rate of 10°C/min. (3) Soldering heat resistance According to JIS C-6481. (4) Insulation resistance Based on JIS C-6481.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a laminate plate provided with punched holes for measuring the amount of shrinkage of the punched holes.

Claims (1)

[Claims] 1 In a thermosetting resin laminate obtained by combining multiple prepregs whose base material is impregnated with thermosetting resin and dried, cellulose fiber base prepreg is applied to both surface layers and hydroxylated to the middle layer. A thermosetting resin laminate with good punching workability, which is made by arranging aluminum-mixed cellulose fiber base material prepreg and laminating it under heat and pressure.