JPH0132761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a prepreg used for laminates such as insulating boards, copper-clad laminates, and decorative laminates.
Prepreg is produced by impregnating a base material for a laminate such as paper, organic/inorganic natural fiber, glass fiber, chemical fiber cloth, nonwoven fabric, etc. with a thermosetting resin varnish and drying it in a drying oven to a B state.

Conventionally, as a method for drying a base material impregnated with a thermosetting resin varnish, a method of forcibly blowing and circulating hot air has generally been used. That is, the first
As shown in the figure, heated air is blown from nozzles 1 arranged opposite to each other, and the impregnated base material 2 is passed through the nozzles 1 and dried. 3 is a thermosetting resin varnish impregnation tank.

In this case, since the heated air is directly blown onto the base material, a phenomenon of fluttering of the base material occurs in the drying tower when producing prepregs with relatively high resin content and thin base material thickness. Further, there is a drawback that the sheet surface cannot be finished smoothly because air is easily blown unevenly on the impregnated sheet surface.

In addition, as a method to minimize these problems, there is a method of suppressing the blowing speed of hot air to a low level, but in this case, the temperature variation within the tower becomes large, resulting in localized uneven hardening of the prepreg. On the other hand, a major disadvantage of drying using the hot air circulation method is that when a relatively low boiling point curing agent and accelerator are used as the base varnish, these curing agents and accelerators scatter before sufficient curing progresses. This causes abnormal hardening of the prepreg. In other words, when drying a varnish that is blended with a fixed amount of resin, curing agent, accelerator, solvent, etc. and controlled to a specified gel point, the drying temperature and time and the progress of the B state of the prepreg are approximately the same as the temperature and time. Curing progresses proportionately. However, if the curing agent accelerator or the like scatters and becomes insufficient, the drying temperature dependence of the prepreg decreases, resulting in insufficient curing.

These problems have a negative effect on the flowability of the resin during the prepreg molding process, causing deterioration in the thickness accuracy of laminated molded products and poor air bubble inclusion, which can lead to serious defects in the properties of the molded product. Become.

In addition, natural convection drying using a pipe heater is susceptible to the influence of outside air temperature, and in particular, the flexible air flows in from the bottom opening, causing large variations in the temperature inside the tower.Also, the airflow flowing into the dryer causes the impregnated base material to flutter. occurs. Another drawback is that it is difficult to heat uniformly.

The present invention has been made in view of these points, and consists of a base material impregnated with thermosetting resin varnish, which is placed between a pair of radiant plates facing each other at a constant interval and having hot air blown onto the back surface. It is characterized by being passed through and dried.

As the radiation plate, an iron plate, a copper plate, or an aluminum plate is used. The thickness is about 1 mm, the width is the same as the base material, or slightly wider, and is 1 to 1.5 mm.
mm, and the length is preferably about 1 to 5 mm.

If the surface of the radiant plate facing the base material is black-treated, that is, a black heat-resistant paint is applied, the thermal efficiency will be excellent. Hot air with a temperature of 140 to 180°C is used.

FIG. 2 shows a drying oven showing the method of the present invention, and 4 is a radiant plate. The radiant plates 4 are arranged facing each other with an interval of 50 to 150 mm.

The moving speed of the substrate is the same as in the case of a normal drying oven, and is preferably 10 to 20 m per minute.

Example A pair of iron plates made of 0.1 mm thick glass woven fabric impregnated with epoxy resin varnish (resin content 60% by weight), placed facing each other with a 100 mm interval, and 150°C hot air blown onto the back side. A prepreg was obtained by drying the prepreg. Copper foil was layered on both sides of the four sheets of prepreg, and the whole was heated and pressed to produce a laminate for a multilayer printed wiring board. This laminate was void-free and had excellent plate thickness accuracy and electrical properties.

As explained above, in the present invention, since the base material can be heated uniformly, a prepreg plate can be manufactured that has no uneven coating, uneven heating, no voids, and has excellent plate thickness accuracy and electrical properties. is obtained.

The present invention is particularly effective for producing prepregs with a relatively high resin content and a thin base material.

[Brief explanation of drawings]

The drawings show simplified sectional views of drying ovens, with FIG. 1 showing the conventional case and FIG. 2 showing the case of the present invention. Explanation of symbols: 1... Nozzle, 2... Base material, 3... Thermosetting resin varnish impregnation tank, 4... Radiation plate.

Claims (1)

[Claims] 1 In a drying room, radiant plates 4 are arranged facing each other at regular intervals, and hot air is blown onto the non-opposed surfaces of the radiant plates 4 to heat the radiant plates 4, and the base material 2 impregnated with thermosetting resin varnish is heated. A prepreg manufacturing method characterized in that the prepreg is dried by passing between opposing surfaces of the radiation plate 4.