JP2008080560A - Method for manufacturing metal-clad laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a metal-clad laminated sheet capable of suppressing warpage and dimensional change during heating process when a printed-wiring board is manufactured. <P>SOLUTION: A prepreg and a metal foil are superposed, and it is pressed under heating by making a pressure until time when a thermosetting resin starts to melt not higher than 0.3 MPa. Then, it is pressed under heating under a specified pressure from starting of melting to gelation, and after the pressure is lowered by 0.5-2 MPa/min, heating is performed under no pressure condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a metal-clad laminate useful for printed wiring boards and the like.

  Conventionally, in the manufacture of metal-clad laminates for printed wiring boards, etc., multiple prepregs obtained by impregnating and drying a thermosetting resin such as epoxy resin or phenol resin on a fiber substrate such as glass cloth A method of heating and press-molding a metal such as copper foil as the outermost layer is well known. With respect to this method, various attempts have been made to suppress the occurrence of warpage, dimensional change, variation, and the like in the heating process when a printed wiring board is manufactured using a metal-clad laminate. For example, annealing may be performed after molding, or heat pressing may be performed at a lower pressure.

  However, even with these improvement measures, it is difficult to prevent warpage occurring in the product on the pressure hot plate side in the formation of a large number of sheets, and discoloration and rusting of the product are seen due to reheating in the annealing process. There was a problem. Therefore, as a means for suppressing the warpage and dimensional change of the product without causing such problems, the resin constituting the prepreg is heated and pressurized at a pressure of 0.3 MPa or less until gelation starts, and gelation starts from the start of melting. Until now, a method of heating and pressurizing at a normal predetermined pressure and then heating without pressure has been proposed (Patent Document 1). Also, a method to control the heating rate and pressure during molding in relation to the temperature and melt viscosity of the prepreg resin (patented) for the purpose of suppressing the deterioration of moldability due to variations in heating temperature and variations in sheet thickness. Document 2) has also been proposed.

However, even in such a proposed method, it is not always practically satisfactory to produce a metal-clad laminate that can suppress warpage and dimensional change in the heating process during printed wiring board production. . For example, although the method of Patent Document 1 has been confirmed to have a certain effect, even in this method, the warpage and dimensional change may be increased and the product specifications may be deteriorated.
JP-A-6-71773 Japanese Patent No. 3382169

  The present invention eliminates the conventional problems from the background as described above, and in the production of metal-clad laminates, warp and dimensional changes in the heating process during the production of printed wiring boards based on good formability. It is an object of the present invention to provide a new and improved method that can more effectively suppress the occurrence of.

  The method for producing a metal-clad laminate of the present invention is characterized by the following as a solution to the above-mentioned problems.

  First: A plurality of prepregs obtained by impregnating and drying a thermosetting resin on a fiber base material are stacked, and a metal foil is further stacked on the outside, and the pressure until the thermosetting resin starts to melt is 0.3 MPa or less. The pressure is heated and pressurized at a contact pressure of 1, 2 hours until the thermosetting resin starts to melt and gels, and then the pressure is reduced at 0.5 to 2 MPa / min and heated in a non-pressure state.

  Second: In the above method, the cooling rate after heating in a pressureless state is 3 ° C./min or less.

  According to the first aspect of the present invention, by adopting a specific molding process for controlling the step-down speed after gelation of the thermosetting resin to be in a specific range of 0.5 to 2 MPa / min, for example, printed wiring The warp after heating in the heating process at the time of manufacturing the plate is suppressed to 0.5 mm or less and the dimensional change is suppressed to a low level of less than 0.001, and the metal-clad laminate can be manufactured with good formability.

  Moreover, according to the 2nd invention which controls the cooling rate after pressureless shaping | molding to 3 degrees C / min or less, it becomes possible to implement | achieve the said effect more reliably and stably.

  In the method for producing a metal-clad laminate of the present invention, the fiber base material, the thermosetting resin, and the metal foil may be various types including those conventionally known. The same applies to the means for heating and pressurizing.

  For example, as a fiber base material, those generally used for laminated sheets of glass fiber, synthetic fiber, natural fiber, etc., and for thermosetting resins, epoxy resin, phenol resin, polyester resin, ferene oxide are used. It may be various kinds used for laminated plates such as resin and fluororesin. These thermosetting resins may be applied as a composition containing various compounding components when impregnated in the fiber base. For example, compounding components such as a curing agent, a curing accelerator, a flame retardant, an inorganic filler, a viscosity modifier, and a colorant may be considered.

  The thermosetting resin is impregnated into a fiber base material as a composition with these components and dried to form a semi-cured so-called B-stage state, thereby constituting a prepreg.

  In the present invention, a necessary plurality of such prepregs are used and stacked, and a metal foil made of a metal or alloy such as copper or nickel is stacked on the outside thereof. The amount of impregnation of thermosetting resin and compounding components, the thickness and number of prepregs, the type and thickness of metal foil, etc., as one of various forms as before, depending on the use or required properties of the laminate You can choose.

  After stacking as described above, it is laminated by heating and pressing, but due to the difference between the thermal expansion coefficient and elastic modulus of the fiber base material, thermosetting resin, and metal foil, the laminated sheet is molded by heating and pressing. Tends to warp and change dimensions. For this reason, in this invention, this shaping | molding is performed by the following processes and conditions as mentioned above.

  A: The pressure until the thermosetting resin starts to melt is heated and pressurized with a contact pressure of 0.3 MPa or less.

  B: Heat and pressurize at a predetermined pressure until the thermosetting resin starts to melt and gels.

  C: Thereafter, the pressure is reduced at 0.5 to 2 MPa / min.

  D: Heating is performed under no pressure.

  In process A, it is inherently desirable to heat in a non-pressure state, but since it is necessary to contact the upper and lower hot plates in order to heat, the minimum pressure for performing this heat transfer is 0.3 MPa or less. As a result, stress due to contact of materials having different thermal expansion coefficients and elastic moduli is reduced.

  In the next process B, in the fluid state until the thermosetting resin is melted, plastically deformed and gelled, a pressurizing force is required according to the type and viscosity of the thermosetting resin. Moreover, the required heating for gel hardening is required.

  For example, in the case where the thermosetting resin is an epoxy resin, and the laminated sheet using glass cloth and copper foil has a thickness of about 1.2 to 2 mm, for example, 100 ° C. to 180 ° C., 2 to 10 MPa. Heating and pressing are performed for about 10 to 30 minutes.

  In the above processes A and B, the viscosity change due to temperature is measured by a known means, for example, using a solid meter or the like, whereby the start of melting or gelation can be determined.

  The process B is followed by the process D until the heating in the non-pressure state. The process C needs to be performed under the pressure-decreasing condition in the range of 0.5 to 2 MPa / min as the process C.

  Under fast conditions where the pressure reduction rate exceeds 2 MPa / min, the warpage of the laminate increases due to a sudden stress change. On the other hand, under slow conditions of less than 0.5 MPa / min, resin curing proceeds too much, and it is difficult to suppress warpage and dimensional change even by heating under no pressure in Process D, which is worse.

  The heating under the non-pressure of the process D is the same as the temperature range in the process B described above. This process D is also indispensable in the present invention.

  In the present invention, by setting the cooling rate after this process D to 3 ° C./min or less, the temperature difference between the front and the back during cooling of the laminate can be minimized and the composition of the polymer can be made uniform. it can. For this reason, the effect of suppressing warpage and dimensional change is further ensured. In practice, this cooling rate is considered to be 0.5 ° C./min or more from the viewpoint of productivity. When the cooling rate is 3 ° C./min or less, a synergistic effect with the process C is obtained.

  Then, an Example is shown below and it demonstrates in detail. Of course, the present invention is not limited to the following examples.

(1) Preparation of resin varnish A varnish having the following composition (parts by weight) was prepared.

Bisphenol A epoxy resin with epoxy equivalent of 500 (150 parts)
Dicyandiamide (3 parts)
2-Ethyl-4-methylimidazole (0.1 part)
Methyl ethyl ketone (30 parts)
DMF (10 parts)
Dimethyl cellosolve (10 parts)
(2) Impregnation and drying The above resin varnish was impregnated into 2116 type glass cloth and dried at 160 ° C. for 7 minutes to obtain a prepreg having a resin impregnation ratio of 50%.

(3) Molding Two prepregs are stacked, and a copper foil having a thickness of 18 μm is stacked on both sides thereof.
a: Hold at a press pressure of 0.3 MPa at 175 ° C. until the resin starts to melt,
b: When the resin started to melt, it was heated and pressurized at a press pressure of 5 MPa until the gel was cured at a temperature of 175 ° C.

c: After gel curing, the pressure is reduced at the pressure reduction rate shown in Table 1,
d: Heated at a temperature of 175 ° C. for 20 minutes without pressure.

  e: Thereafter, the temperature was lowered at the cooling rate shown in Table 1.

(4) Evaluation A test piece of 250 × 250 mm was prepared for the copper clad laminate obtained by the above process, and the warpage and dimensional change after heating at 140 ° C. for 30 minutes corresponding to the heating process at the time of manufacturing the printed wiring board were performed. It was measured.

  Warpage was measured with a dial gauge at the four corners. In addition, the dimensional change was obtained by determining the rate of change after heating with reference to the measured value in the normal state.

  The results are also shown in Table 1.

  In the examples of the present invention, it was confirmed that both warpage and dimensional change were significantly suppressed.

Claims (2)

  A plurality of prepregs obtained by impregnating and drying a thermosetting resin on a fiber base material are stacked, a metal foil is further stacked on the outside, and a contact pressure of 0.3 MPa or less until the thermosetting resin starts to melt. After heating and pressurizing at a predetermined pressure until the thermosetting resin starts to melt and gel, the pressure is reduced at 0.5 to 2 MPa / min and heated in a non-pressure state. A method for producing a metal-clad laminate.   The method for producing a metal-clad laminate according to claim 1, wherein the cooling rate after heating in a non-pressure state is 3 ° C./min or less.