JPS639760B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method for manufacturing copper-clad laminates for printed wiring. Conventionally, copper-clad laminates for printed wiring have been made using room-temperature liquid resins diluted with solvents, such as epoxy resins and phenols, on fiber base materials such as woven fabrics, non-woven fabrics, and paper materials made of glass fibers, organic fibers, and wood pulp. A so-called B-stage prepreg is created by impregnating and coating a resin, unsaturated polyester resin, etc., removing the solvent in a dryer, etc., and proceeding with the reaction. After cutting this into a predetermined size, copper foil is coated on the surface. Generally, they are stacked and sandwiched between mirror plates and heated and pressed between multiple parallel heating plates.

This conventional manufacturing method has the advantage of producing a good substrate with excellent characteristics as a wiring board, but it requires a large amount of solvent for coating the other side, and a large amount of energy is required for drying, resulting in a large loss of materials and energy. This also causes problems such as environmental pollution due to the scattering of solvents.

For this reason, various methods of making laminates using solvent-free resins have been studied. Examples include a method using a sheet-shaped molding material, an application of a pultrusion molding method, and a method in which molding is performed using a calender roll, a belt press, or the like. These methods have technical problems such as warping easily occurring due to local orientation of the base material as the material flows during press molding, and it being difficult to remove voids because it is difficult to apply sufficient pressure to the base material. In addition, it also requires a step of uniformly impregnating the base material, making it unsatisfactory compared to conventional methods in terms of cost. On the other hand, in general FRP, a solvent-free liquid resin is supplied to the fiber base material while the fiber base material is already impregnated, and impregnation and molding are performed simultaneously in a mold.
It exists as a molding method. These methods include the matte die method and the cold press molding method, but even if these methods were applied as they were to copper-clad laminates for printed wiring with highly required characteristics, they were insufficient to produce a board with no voids and less warpage.

In view of the above circumstances, the present invention was made as a result of intensive research into a simple and convenient manufacturing method for a copper-clad laminate for printed wiring, which is free from warpage and voids, using a solvent-free thermosetting resin. .

That is, in the present invention, a fiber base material is used as a base material, a solvent-free thermosetting resin is partially supplied to the base material, a copper foil is layered on the surface, and then a peripheral edge of at least one of a pair of parallel plates is coated. In a method for manufacturing a copper-clad laminate for printed wiring, which uses a mold having protrusions on its parts and hot-press-forms the base material in a state where it is held between the protrusions,
The present invention is characterized by preheating and molding copper foil, and uses a solvent-free thermosetting resin to provide a copper-clad laminate for printed wiring with excellent properties.

In other words, the present invention prevents the occurrence of sagging in the copper foil by supplying preheated copper foil in a flat state without sagging and then hot-pressing it in a heated mold to allow the copper foil to elongate due to thermal expansion. The problem of copper foil creases has been solved by preventing them from occurring.

The preheating temperature of the copper foil is preferably the same as the molding temperature, but even if it is lower than the molding temperature, the effect is significant by reducing the elongation and sagging of the copper foil due to thermal expansion. It is also a good idea to preheat the copper foil at a temperature higher than the molding temperature to prepare for cooling the copper foil after it is placed on the surface of the base material partially supplied with the thermosetting resin. The molding temperature is preferably ±60°C, more preferably ±30°C. The method for preheating the copper foil is not limited as long as it can uniformly heat the copper foil, such as infrared heating or steam heating. Preheating using a heating plate or mold is also a simple method. Preheating is not limited to just the copper foil, but it is also good to quickly preheat the base material partially supplied with the thermosetting resin.

Copper foil is generally supplied after being cut into a predetermined shape, but it may also be continuously supplied to the hot platen in the form of a roll. In this case, it is necessary to preheat the copper foil close to the surface to be hot-press-molded using a mold having protrusions to prevent sagging on the surface of the copper foil to be hot-press-molded.

By the way, in the present invention, the resin is not supplied to the entire surface of the base material, but is introduced into the mold in a state where it is partially supplied to a portion close to a position corresponding to the center of the mold. The resin supplied to the center receives heat during hot press and becomes lower in viscosity, flows toward the periphery of the mold under pressure, and spreads throughout the entire mold.The damming effect at the pinch area eventually reduces the internal pressure. and sufficient impregnation of the substrate is achieved. If the resin is supplied to the entire surface of the base material, the flow of the resin will be reduced and the air bubbles will not be sufficiently expelled. The area in contact with the mold of the part to be molded receives the heat of the mold and causes a curing reaction of the resin, making that part unsuitable for molding and resulting in a very poor yield. A preferred form of this supply is to supply the material to a central portion of the mold that is inside the protrusion on the periphery of the mold, preferably to a portion that is approximately 30 mm or more inside.

Next, the solvent-free thermosetting resin used in the present invention is a thermosetting resin such as epoxy, unsaturated polyester, or phenolic resin that does not contain a solvent.
As the fiber base material, woven fabrics such as cloth made of glass fibers, nonwoven fabrics such as swirl mats, paper-like materials, and woven fabrics, non-woven fabrics, and paper-like materials made of organic fibers, wood pulp, etc. are used. Solvent-free thermosetting resins that do not contain crosslinking monomers, such as unsaturated polyesters, are often solid or semi-solid with very high viscosity at room temperature. In such a case, the resin can be supplied by heating and melting the resin in advance to reduce its viscosity, and then mixing the resin with a curing agent, filler, etc. By the way, the thermosetting resin mixture used in this method has a melt viscosity of 0.1 to 50 at the molding temperature.
Resins in the poise range are preferred. If the viscosity is too low, less than 0.1 poise, it will be difficult for the internal pressure to rise during molding, and sufficient impregnation will not be achieved, resulting in a substrate with many poids. This is because even if the protrusions of the present invention are sufficiently tightened, it is impossible to completely eliminate the gaps between the base materials at the clamping portion, and the lower the viscosity, the more likely the resin will leak from the gaps. This varies depending on the type of base material used, but bulkier base materials such as non-woven fabrics and paper-like materials are more likely to build up internal pressure than woven fabrics such as cloth, making it easier to mold with low-viscosity resin. I found it to be easier. On the other hand, if the viscosity exceeds 50 poise and the viscosity is too high, the internal pressure will tend to rise, but the impregnation into the fibers will decrease, and the base material will also tend to flow as the resin is washed away during hot pressing. As a result, the base material is shifted and localized, and the warpage of the formed plate increases. Woven fabrics are good for this substrate flow, and nonwoven fabrics and paper-like substrates made of long fibers are more resistant and advantageous.

As the base material, the various base materials described above may be used alone or in combination. In particular, it is preferable to use a woven fabric such as glass cloth as the surface material and a non-woven fabric such as swirl mat or a paper-like material as the internal core material layer. The reason for this is, as mentioned above, that non-woven fabrics and paper-like materials used as core material layers tend to have internal pressure build-up even under the same constricting pressure and have good impregnating properties, but are disadvantageous in terms of substrate flow. Therefore, if a woven fabric is placed on the surface in order to prevent the substrate from being disturbed on the surface, which is susceptible to warpage, it will be easier to form a plate with good impregnability and warpage. Further, by adopting such an arrangement, the strong woven fabric layer is placed on the surface, which is advantageous because the strength such as the bending strength of the plate can be increased.

As explained above, according to the method of the present invention, a preheated copper foil is layered on the surface of a base material partially supplied with a thermosetting resin, and hot pressure molding is performed using a mold to form a solvent-free type. A good copper-clad laminate for printed wiring without folded copper foil can be manufactured using resin.

This will be explained in detail below based on examples.

Example 1 A solvent-free epoxy resin (trade name: Araldite 8011, manufactured by Ciba Corporation) that is solid at room temperature is melted and liquefied at 110°C in a heating container, and an acid anhydride curing agent (trade name: HN-2200, manufactured by Hitachi Chemical) is placed in another container. ) and an accelerator (benzyldimethylamine) were prepared in a liquid state at room temperature. From this container, 100 parts of resin, 33 parts of curing agent, and 1.5 parts of accelerator were weighed out and mixed by stirring using a stirrer. 400g of mixed resin, 520mm square, basis weight 100g/
⁴ sheets of glass paper (manufactured by Nippon Vilene Co., Ltd.)
EP4401) was cast onto the center of the base material, and pressed with a parallel plate at room temperature to a thickness of about 5 mm to obtain a sheet-like product with a flat surface.

Layer 18μ thick copper foil that has been preheated in a dryer at 180℃ on both surfaces of this, and place this on the bottom mold with a thickness of 510mm.
The upper mold was a square flat plate with a 510 mm square plate and a belt-like protrusion of 1.1 mm in height and 5 mm in width was placed around the inner periphery of the mold, and the mold was immediately hot-pressed. The mold temperature at this time was 170°C for both the upper and lower molds, the mold was clamped for 30 seconds, and molding was carried out for 5 minutes at a maximum pressure of 80 kg/cm ² applied to the hot platen. The copper foil surface of the obtained copper-clad laminate showed no creases and could be suitably used as a printed wiring board.

Comparative Example 1 A copper-clad laminate was molded in exactly the same manner as in Example 1, except that copper foil at room temperature was supplied. The copper foil surface of the obtained laminate had many folds of copper foil with a length of 3 to 10 cm.

As mentioned above, this method solves the problem of copper foil creases by preheating the copper foil before supplying it, and also produces copper-clad laminates for printed wiring using solvent-free thermosetting resin. Because it makes it possible to manufacture a coating material, it does not require a solvent for coating as in conventional coating methods, and it does not require drying energy to remove the solvent, which has a great effect on saving materials and energy. The molding method is also simple and convenient.

Claims (1)

[Claims] 1 Copper foil preheated to a molding temperature of ±60°C is layered on the surface of a fiber base material partially supplied with a solvent-free thermosetting resin, and then this is layered with a pair of copper foils, at least one of which has a band-shaped protrusion on the periphery. 1. A method for producing a copper-clad laminate for printed wiring, characterized in that the periphery of the base material is subjected to hot-press molding using a parallel disk mold in a state where the periphery of the base material is held between the protrusions.