Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1996-05-01
1997-11-18
Gallagher, John J.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156281, 156288, 156312, 156313, 156323, 428 76, B32B 3100
Patent
active
056883501
DESCRIPTION:
BRIEF SUMMARY
This invention relates to laminates and printed circuit boards and more specifically to components employed in the manufacturing of such laminates.
BACKGROUND OF THE INVENTION
1) Field of the Invention
A printed circuit board laminate normally includes, as a component, several layers of a resin impregnated woven glass fiber cloth known as prepreg. On opposite sides of the prepreg are conductive copper foil sheets which are subsequently etched to produce the conductive tracks.
In the manufacturing process called lay-up, the requisite number of sheets of copper foil and prepreg are assembled onto a pressplate. A stack of such lay-ups is often built up. This stack is often called a book. The entire book is heated under pressure to bond the prepreg to the copper foil. After cooling, the sheets of laminate are separated and subjected to further processing.
2) Description of the Prior Art
FIG. 1 exemplifies the prior art lay-up process, in which prepreg sheets 1 and copper foils 2 are assembled between pressure plates 3.
One of the chief causes of contamination is the presence of resin dust and glass fibers from earlier processing of the prepreg. Because the prepreg is handled in the same area, particles of resin dust from the air land on the surface of the copper foil and press plates. Some particles remain even after wiping and during the pressing these particles melt and adhere to the surfaces.
This causes resin spots on the surface of the foil which prevent satisfactory etching of the copper. These spots can also cause pits and dents in the surface of the copper during the lamination process. If the press plates become contaminated with fused resin spots, they cause dents on the surface of the laminate each time they are used. The resin spots are very difficult to remove from the press plates except by severe abrasion which makes the press plates thinner and shortens their useful life.
One object of the present invention is to provide a method of lay-up which prevents any resin dust created in subsequent handling from being carried in the air onto the press plates. Another aspect is to allow the surfaces of the copper foil, especially thinner foils such as 1/2 oz foils, to be cleaned without wrinkling or damage prior to being assembled in the book.
SUMMARY OF THE INVENTION
The present invention provides a method of forming a metal-faced laminate, comprising forming a stack of plastics sheets between a pair of sheets of metal foil, applying heat and pressure to the edges of the stack to fuse the edges so as to form a sealed edge around the stack to form a sealed unit, cleaning the surfaces of the sheets of metal foil and subsequently heating the sealed unit while applying pressure to its major surfaces to fuse the stack into a laminate.
Preferably, the sealed edge is formed by applying sufficient heat in the area of the edge to melt the plastics material locally, and sufficient pressure to the area of the edge to press the metal foil sheets substantially together.
Preferably, the plastics sheets are resin impregnated woven glass fiber prepregs and the metal foil is of copper.
Preferably, the two heating and pressing steps are carried out in physically separated locations.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic side view illustrating a prior art lay-up procedure;
FIG. 2 is a schematic side view of an apparatus for forming a sealed unit;
FIGS. 3a and 3b are plan and side views, respectively, of the sealed unit formed by the apparatus of FIG. 2;
FIG. 4 is a schematic side view of a lay-up apparatus; and
FIG. 5 illustrates the lay-up step of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring to FIG. 2, a number of prepreg sheets 10 are arranged in a stack 14 between copper foils 12 within a sealing apparatus. The sealing apparatus comprises a table 16 on which the stack 14 is placed, and a resilient compression pad 18 which is movable relati
REFERENCES:
patent: 3932250 (1976-01-01), Sato et al.
Database WPI, Week 8921, Derwent Publications Ltd., London, GB; AN 89-153785 & JP,A,1 093 316 (Matsushita Elec Works) 12 Apr. 1989.
Patent Abstracts of Japan, vol. 15, No. 393 (M-1165) 4 Oct. 1991 & JP,A,03 161 198 (Matsushita Electric Works Ltd) 11 Jul. 1991.
Database WPI, Week 8820, Derwent Publications Ltd., London, GB; AN 88-136288 & JP,A,63 077 732 (Hitachi KK) 7 Apr. 1988.
Cannon Roy
Hamilton Sheila
Kennett Jonathan
Robertson Stewart
Gallagher John J.
Teknek Electronics Limited
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