JPH04325246A - Continuous manufacture of metallic foil-clad laminated board - Google Patents

Abstract

PURPOSE:To prevent pollution by an excess resin liquid, and to reduce residual strain by a method wherein a plurality of continuous sheet-shaped base materials are laminated and unified, a metallic foil is lined on a laminate while the laminate is preheated and cured and the laminate is cured without pressing and cut. CONSTITUTION:When metallic foil-clad laminated boards are manufactured continuously, continuous-sheet base materials 1 containing a liquid cured resin generating no volatile reaction by-product at the time of curing in 100-108% of the quantity of saturation are laminated and unified by laminating rolls 6 first. A metallic foil 8 is lined on at least one surface of a laminate by an endless belt loop 12 wound between each roll 13, 13' of a double belt press 11. The laminate is preheated in a preheating zone 10 as the fluidity of the impregnated liquid resin is left as it is kept before and behind the metallic foil 8. The preheated laminate is pressed and heated in pressing zones 7, 14 and cured. The cured laminate is released from said press 11, and cured without pressing by a curing oven 15. A cured laminated board 20 is cut.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for continuous production of rigid-type single-sided or double-sided metal foil-clad laminates for use in printed circuit boards.

(Prior art and its problems) Conventionally, metal foil-clad laminates have been manufactured by impregnating a base material with resin varnish, layering the required number of prepregs obtained by drying with metal foil, and compressing with a press. Batch-type dry molding methods have been the mainstream, but continuous methods that demonstrate high productivity are attracting attention.

[0003] As one of them, the present applicant's patent application
No. 126418 (Japanese Patent Publication No. 62-6513) is a method of impregnating a plurality of continuous sheet-like substrates with a liquid thermosetting resin liquid, such as an unsaturated polyester resin liquid, which does not generate volatile by-products during the curing reaction process, while being transported. Then, these are laminated and combined,
Disclosed is a method for manufacturing a metal foil-clad laminate (wet pressureless continuous method) in which metal foil is applied to a laminate and then continuously cured without applying molding pressure. However, with the recent development of electrical and electronic equipment, the performance required of laminates has become increasingly strict, and there is a particular desire for improved properties under heat. For this purpose, it is effective to reduce the resin content of the laminate and increase the proportion of the base material, but this tends to be difficult to achieve in the pressureless continuous method since no substantial molding pressure is applied during curing. In addition, in the pressureless continuous method, the relative movement between the metal foil and the base material layer is free at the initial stage of curing, so the metal foil may sag or wrinkle due to the difference in thermal expansion coefficient or vibration between the two. is likely to occur.

[0004] Therefore, continuous pressurization using a double belt press, in which the laminate is sandwiched between a pair of endless belts from both sides and the laminate and the belts are moved synchronously in the same direction, pressurizes and heats the laminate to cure it. A wet method has been developed and disclosed in JP-A-56-144151 (JP-A-60-58031), and more recently in JP-A-2-6131, JP-A-2-59343, and JP-A-2-86441.

However, in these pressurized continuous wet methods, consideration must be given to the amount of resin impregnated into the base material before lamination, which is different from that in the pressureless continuous method. In other words, in the pressureless continuous method, no pressure is applied during curing, so air is likely to be trapped between each base material layer and between the base material and metal foil, and to prevent this, excessive resin liquid is supplied to form an interlayer resin layer. However, in the pressurized continuous method, excess resin liquid is squeezed out by the double belt press and contaminates the apparatus itself and surrounding equipment. Further, the continuous pressurization method according to the prior art tends to cause problems such as blistering and deformation due to heating during processing of the laminate into a printed circuit board and during use.

(Solution Method) The present invention solves the above problems. Therefore, the present invention provides (a) a saturated amount of a liquid curable resin that does not generate volatile reaction by-products during curing.
(b) applying metal foil to at least one side of the laminate; (c) applying impregnated liquid resin before or after applying the metal foil; a step of preheating the laminate while maintaining fluidity;
(d) the step of curing the preheated laminate by applying pressure and heat in the press zone of the double belt press; (e) the step of releasing the cured laminate from the double belt press and curing it without applying pressure; (f) Provided is a method for continuous production of a metal foil-clad laminate, characterized in that the step of cutting the cured laminate into predetermined dimensions is carried out in-line while the sheet-like base material and the laminate are continuously conveyed.

[0007] When heating the laminate by applying a high forming pressure from the beginning in a double belt press, it is not possible to relieve the internal stress due to the difference in thermal expansion coefficient between the metal foil and the rest. In addition, volatile components, such as crosslinking monomers such as styrene in the case of unsaturated polyester resins, may evaporate all at once, causing problems such as blistering, delamination, and foaming. It is advantageous to preheat before reaching . However, it is preferred that the resin of the laminate entering the press zone of the double belt press does not lose its fluidity. Further, when the laminate is completely cured under pressure in the press zone of a double belt press, internal stress due to shrinkage and the like due to curing of the resin tends to remain. It is therefore advantageous for the last stage of curing to be substantially complete after the laminate has been released from the double belt. In this way, by adding the steps of preheating the laminate before entering the press zone of the double belt press and post-curing after releasing it from the double belt press, residual distortion in the product laminate can be reduced.

(Preferred Embodiments) Preferred embodiments of the present invention will be explained with reference to the drawings. The layout of an example of a device used for carrying out the method according to the invention, shown in FIG. JP-A-56-1 cited above except that the post-curing furnace 15 is added.
The device may be the same as the device disclosed in No. 44151 or the like. Therefore, the impregnated portion of the base material is omitted from the drawings.

As shown in the figure, the double belt press 11 of the present invention produces a laminate of a plurality of resin-impregnated base materials 1 which are combined by a lamination roll 6 between them, and a metal foil 8 laminated on the upper surface thereof. It includes a pair of upper and lower endless belt loops 12 that are sandwiched and run. Each endless belt loop 12 consists of a steel belt stretched between rolls 13, 13' and is driven synchronously with the conveying speed of the laminate. Endless belt loop 1 for each person
2, a preheating zone 10, a pressure roll 7 and a pressure box 14 are provided, respectively. The preheating zone 10 is a heating chamber in which hot air or a heating medium circulates, and heats the laminated plates held between the belts 12, 12. In combination with the preheating zone, the upstream rolls 13 of the double belt press may be heated by hot air, heating medium or steam, thereby saving the length of the preheating zone. If the pressure roll 7 swells or peels between layers due to preheating, it is removed. Pressure box 14 is preferably divided into sections with partition plates that confine pressurized gas or liquid and allow for independent temperature control. Instead of a pressurization box divided into multiple sections, a plurality of independent pressurization boxes may be installed in parallel to control temperature and/or pressure. The laminate is heat cured under pressure while passing through a pressurized area by a press box. Instead of the pressure box, the pressure may be applied using a plurality of pairs of rolls.

[0010] Laminated plate 20 coming out of the double belt press 11
passes through the post-hardening furnace 15 under no pressure, and after at least part of the internal stress is relieved, it is cut into a predetermined size.

A device with another layout is shown in FIG. The apparatus of FIG. 2 is similar to the one shown in FIG.
It is the same as the device.

[0012] Preheating prevents the laminate from blistering due to rapid heating.
Since this is carried out to avoid delamination, foaming, etc., it is preferable not to proceed with curing in this step to the point where the impregnated resin liquid no longer exhibits fluidity. Therefore heating zone 1
It is appropriate that the length of the press zone 0 is set in a range of 0.25 to 2 times, preferably 0.3 to 1.2 times, the length of the press zone formed by the pressure box 14. The heating temperature of the laminate is generally 80 to 110°C.

The specific example shown in FIG. 1 is for a single-sided metal foil-clad laminate, but in the case of a double-sided plate, it goes without saying that the metal foil 8 is symmetrically laminated on the lower surface as well. Furthermore, the lamination of the metal foil 8 may be carried out using a separate laminating roll 9 intermediate the double belt press entrance and the laminating roll 6, as in the apparatus of FIG. Also, adhesive may be applied to the metal foil 8 immediately before lamination, but
Preferably, a metal foil is used which has been previously applied with adhesive off-line.

[0014] In the present invention, linter paper is used as the base material.
Cellulose base materials such as kraft paper, glass cloth, glass paper, mixed paper, nonwoven fabric, etc. can be used. These base materials can be conveyed in parallel in a plurality of continuous sheets, individually impregnated with resin liquid, and supplied in-line to the lamination roll 6, or alternatively, once the saturated amount is 100 to 1
A continuous sheet of substrate impregnated with 0.8% resin liquid may be prepared on a separate line and fed to the lamination roll 6.

According to the present invention, the resin content of the resin-impregnated base sheet is adjusted to 100-108% of the saturation amount. Here, the term "saturation amount" refers to the amount of resin sufficient to completely fill the voids in the base material before impregnation. Specific means for adjusting the resin content are described in Japanese Patent Publication No. 1-4729 cited earlier by the present applicant.
7 and Japanese Patent Publication No. 2-9929, it is preferable to impregnate each base sheet with excess resin liquid before laminating and combining, and then scrape off the excess by passing between slits or ironing rollers. . The resin must be a thermosetting resin that is liquid at room temperature and cures without producing volatile by-products, such as unsaturated polyester resins, epoxy acrylate resins, polyester acrylate resins, epoxy resins, etc.

[0016] The resin content of the base material is set to a saturation amount of 100 to 10
By pre-adjusting to 8%, the resin content of the laminate can be reduced and the proportion of the substrate can be increased, and the surrounding equipment will be contaminated by the excess resin liquid squeezed out when pressurized by the double belt press. Never. Furthermore, an impregnated base material with a resin content of 100 to 108% of the saturation amount has low stickiness and can be wound up into a roll. Although the impregnated base material may be wound up as it is, a release paper or the like may be interposed therebetween. In the method of winding up the impregnated base material into a roll, the base material can be impregnated in a separate line, wound up once, and then fed to the continuous pressure method of the present invention, which reduces the length of the line. In addition, the operation becomes easier because an accident that cuts the base material during the impregnation process does not directly lead to a stoppage of the continuous production line.

According to the invention, the laminate is heated at least in steps (c), (d) and (e). However, it is preferable that the preheating in step (c) not proceed to the point where the impregnated resin is hardened to such an extent that it no longer exhibits fluidity. Generally reaction rate is 10% or less, preferably reaction rate is 6
It is desirable to keep it below %. Similarly, the reaction rate in the press zone 14 of the double belt press is generally kept at a reaction rate of 40 to 90%, preferably 60 to 80%. The heating temperature in the press zone depends on the impregnated resin used, but in the case of unsaturated polyester, it is preferably 110 to 160°C, and the molding pressure is 20 kg/c.
m2 or less, preferably 1 to 10 kg/cm2.

Various modifications can be made to the illustrated example as necessary within the scope of the present invention. For example, in the case of single-sided metal foil-clad laminates, a cover sheet such as a polyester film is pasted on the opposite side of the metal foil and peeled off after step (e), or a large number of laminates are cut at once after step (f). A batch annealing step can also be added.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for implementing the invention.

FIG. 2 is a schematic diagram of another apparatus for implementing the invention.

[Explanation of symbols]

1 Resin-impregnated base material 6 Laminated roll 7 Pressure roll 8 Metal foil 10 Preheating zone 12 Endless belt 14 Pressure box 15 Post-curing furnace 20 Laminated board

Claims (5)

[Claims] 1. (a) A step of laminating and combining a plurality of continuous sheet-like substrates impregnated with a saturated amount of 100 to 108% of a liquid curable resin that does not generate volatile reaction by-products during curing, (
b) applying metal foil to at least one side of the laminate; (c)
) Preheating the laminate while maintaining the fluidity of the impregnated liquid resin before or after applying the metal foil; (d) Curing the preheated laminate by heating and applying pressure in the press zone of the double belt press. (e) releasing the cured laminate from the double belt press and curing without applying pressure; and (f) cutting the cured laminate into predetermined dimensions. A continuous manufacturing method for metal foil-clad laminates, characterized in that the method is carried out in-line under continuous conveyance. 2. A claim in which, prior to step (a), a step of individually impregnating a plurality of continuous sheet-like substrates with a resin liquid while being conveyed is carried out in-line with steps (a) to (f). 1
Method described. 3. Impregnation of the continuous sheet-like substrate is carried out in a line separate from steps (a) to (f), and the impregnated substrate is subjected to step (a).
2. The method according to claim 1, wherein the method is supplied to 4. The method according to claim 2 or 3, wherein the resin impregnation rate of the base material is adjusted by impregnating the base material with a resin liquid in excess of the saturation amount, and then squeezing the base material before combining. . 5. The method according to claim 1, further comprising the step of post-curing the cut laminate after step (f).