JPH04325250A - Manufacture of single-sided metallic foil-clad electric laminaed board - Google Patents

Abstract

PURPOSE:To conduct the reduction of the residual strain of a laminated board and the correction of warpage and torsion with excellent productivity in a short time by heating both surfaces of the laminated board only in a short time at a temperature substantially higher than a curing temperature by conduction during a curing process and a cutting process or after the cutting process. CONSTITUTION:A pair of upper and lower endless belt loops 12 travelling while holding the laminate of a plurality of resin-impregnated base materials 1 unified by laminating rolls 6 and a metallic foil 8 laminated on the top faces of the base materials 1 are installed to a double belt press. A preheating zone 10, press rolls 7 and a hydraulic box 14 are mounted into the endless belt loops 12 respectively. On the other hand, a laminated board 20 discharged from the double belt press is passed through a curing over under the state of no-pressure, and passed between a pair of hot plates 16 and cut in specified size by a cutter 17. That is, the laminated board 20 is heated at a higher temperature only in a shoft time by said each hot plate 16 during a curing process and a cutting process or after the cutting process.

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for continuously manufacturing a rigid type single-sided metal foil-clad laminate 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.

[0004] Also, 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 continuous 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.

[0005] Single-sided metal foil-clad laminates have an asymmetric structure, so they tend to warp when heated during processing into printed wiring boards, which may cause trouble in automated component mounting lines. For this reason, for example, the above-cited Japanese Patent Publication No. 62-6513 filed by the present applicant proposes heating the cut laminate in a post-curing chamber to alleviate residual strain, and then correcting warpage and twisting. . However, this process must be carried out in a batch manner and is time consuming, so improvements are desired in order to maintain high productivity in the continuous process.

(Solution Method) The present invention solves the above problems. Therefore, the present invention includes (a) a step of laminating and combining a plurality of continuous sheet-like base materials impregnated with a liquid curable resin that does not generate volatile reaction by-products during curing, and (b) applying metal foil to one side of the laminate. (c) heating and curing the laminate covered with metal foil; and (d) cutting the cured laminate into predetermined dimensions while continuously conveying the sheet-like base material and its laminate. In the method for producing a foil-clad electrical laminate, between the curing step (c) and the cutting step (d) or after the cutting step (d), both surfaces of the laminate are heated by conduction at a temperature substantially higher than the curing temperature. The method is characterized in that it is heated for a short period of time.

[0007] As used herein, "substantially higher temperature" means a temperature difference of at least 50°C. Moreover, "short time" means a time of less than 1 minute, preferably less than 30 seconds, for example 2 to 10 seconds. The transfer rate of thermal energy through conduction is fast, so heating to relieve residual stress only takes a short time.
It becomes possible to carry out in-line with other processes.

(Preferred Embodiment) A preferred embodiment in which the present invention is applied to a continuous wet pressurization method will be described with reference to the drawings. As shown in the figure, the double belt press consists of a pair of upper and lower belts that run while sandwiching a laminate of a plurality of resin-impregnated base materials 1 combined by a lamination roll 6 and, for example, a metal foil 8 laminated on the upper surface thereof. includes endless belt loops 12. 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. In each endless belt loop 12, for example, a preheating zone 10, a pressure roll 7 and a hydraulic box 14 are respectively provided. 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 each 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. The hydraulic box 14 is preferably divided into a plurality of sections with partition plates to enable independent temperature control. Instead of a hydraulic box divided into multiple sections, a plurality of independent hydraulic 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 hydraulic box.

The laminate 20 leaving the double belt press passes through a curing furnace 15 under no pressure, then passes between a pair of hot plates 16, and undergoes a high temperature and short time heat treatment according to the present invention. , cut into a predetermined size by a cutter 17. The degree of hardening of the laminate before heat treatment is 90% or more, preferably 95% or more, so that the effect of heat treatment becomes noticeable.
desirable.

[0010] The heat treatment temperature must be at least 50°C higher than the maximum temperature during the curing process. For example, if the temperature of the curing furnace 15 is 140°C, the hot plate 1
6 can have a surface temperature of 200 to 280°C. Further, it is preferable that the temperature of the hot plate 16 in contact with the metal foil surface of the laminate 20 is 10 to 40° C. higher than the temperature of the hot plate in contact with the opposite surface. The length of the heating zone of the hot plate 16 is such that the laminate 20 passes through it in 1 to 30 seconds, preferably 2 to 6 seconds.

Although the specific example shown is of a wet pressure continuous method, the layout of the apparatus used in the wet pressureless continuous method is disclosed in Japanese Patent Publication No. 62-6513 filed by the present applicant. In that case, a cover sheet is applied to the side of the laminate on which the metal foil is not applied and then cured, but the cover sheet must be peeled off before passing through the hot plate 16. It goes without saying that if a cover sheet is used even in the continuous pressure method using a double belt press, it is peeled off before the heat treatment step of the present invention.

[0012] In the above specific examples, the base material may be a cellulose base material such as linter paper or kraft paper, glass cloth, glass paper, mixed paper, nonwoven fabric, or the like. These base materials can be conveyed in parallel in multiple continuous sheets, individually impregnated with resin liquid, and fed in-line to the lamination roll 6, or alternatively, once wet, the continuous sheets of prepreg are separated. It may also be prepared on the same line and supplied to the laminating roll 6.

(Example 1) Using the illustrated apparatus, seven sheets of kraft paper with a basis weight of 135 g that had been pretreated with melamine resin were impregnated with unsaturated polyester resin, laminated and combined, and then treated with epoxy resin in advance. Apply a resin adhesive and pre-cure 35 micron electrolytic copper foil to one side of the laminate, preheat at 120℃ for 2 minutes, pressurize at 7kg/cm2 with a double belt press, and heat at 140℃ for 1 minute. After heating and pressureless curing at 120° C. for 6 minutes, both sides of the laminate were heated at 260° C. for 3 seconds using a hot plate.

(Example 2) The cured laminate in Example 1 was heated using a hot plate at 260° C. for 3 seconds on the metal foil side and at 230° C. for 3 seconds on the opposite side.

(Example 3) Example 1 except that the heating with the hot plate was changed to 210°C for 10 seconds on both sides.
Same as.

(Comparative Example) Instead of heating with a hot plate in Example 1, heating was performed with hot air at 140° C. for 10 seconds.

The warpage of the laminates of Examples and Comparative Examples was measured immediately after molding and after a portion of the copper foil was removed by etching, and the results shown in Table 1 were obtained.

[Table 1] Note) Sample dimensions are 340mm x 255mm copper remaining percentage
52% For warping, place the product on a surface plate so that the top is concave, measure the four corners, and calculate the average value. The warpage with the copper foil side on the inside was defined as -, and the warpage with the copper foil side on the outside was defined as +.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an 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 Hydraulic box 15 Hardening furnace 16 Hot plate 17 Cutter 20 Laminated board

Claims (3)

[Claims] Claim 1: (a) a step of laminating and combining a plurality of continuous sheet-like substrates impregnated with a liquid curable resin that does not generate volatile reaction by-products during curing; (b) applying metal foil to one side of the laminate; (c) heating and curing the laminate covered with metal foil; and (d) cutting the cured laminate into predetermined dimensions while continuously conveying the sheet-like base material and its laminate. In the method for producing a foil-clad electrical laminate, between the curing step (c) and the cutting step (d) or after the cutting step (d), both surfaces of the laminate are heated by conduction at a temperature substantially higher than the curing temperature. The method described above is characterized in that it is heated for a short period of time. 2. The heating temperature by conduction is 200° C. to 280° C., and the heating time is 1 to 30 seconds.
Method described. 3. The method according to claim 1, wherein the heating temperature on the metal foil side is 10 to 40° C. higher than the heating temperature on the opposite side.