Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1998-03-23
2001-08-28
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S418000, C428S448000, C428S450000, C361S750000, C361S762000
Reexamination Certificate
active
06280851
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to printed circuit boards in general and more specifically to a multilayer product useful for the protection of components employed in the manufacturing of printed circuit boards.
BACKGROUND OF THE INVENTION
In its elementary form, a printed circuit board includes, as a component, a dielectric layer of an epoxy resin-impregnated woven glass fiber body which is known as a “pre-preg.” On one or both sides of the prepreg is bonded a conductive copper foil sheet. Subsequently, much of the copper, through a number of processes, including photographic, is etched away to leave conductive paths on the surface of the prepreg layer. When so assembled, the lamination is often called a core or a board. It is not uncommon to assemble a stack of such boards. The assembly is called a press lay-up and the stack is called a book. An entire press lay-up is heated and subjected to pressure. Upon curing and cooling, the then bonded individual boards are separated from each other and subjected to further processing in well known manners.
Of utmost importance in the manufacturing process is the maintenance of cleanliness or lack of contamination of the copper foil sheets. This is true whether or not the printed ciruit board has one copper layer on one side of a prepreg or is a compound board of numerous layers. A clean environment is one way to avoid, or at least minimize, contamination problems from resin dust, fiberglass fibers, hairs, bugs, and the like, which could cause defects in the copper circuit of the finished printed circuit board.
Another way is to use a protective film as disclosed in U.S. Pat. No. 5,120,590 in which the marginal edges of the protective film are removably joined to a copper foil layer. During use, the entire marginal edge area is cut off and thrown away, creating a substantial waste problem. Alternatively, if the protective film and copper foil are only joined at an end, there is substantial problem with maintaining alignment between the two, resulting in a contaminated copper foil.
Alternatively, U.S. Pat. No. 5,153,050 discloses the use of an aluminum sheet adhered along its marginal edges to two copper foil layers. This system is for use between two epoxy resin-impregnated woven glass fiber bodies. The aluminum sheet is generally thrown away leading to increased waste disposal. There have been substantial problems with panel alignment both before and during pressing as well as image transfer problems.
Other attempts at solving the same problems, while avoiding some of the drawbacks of the above systems, have failed to be commercially viable, apparently due to inoperativeness. For example, U.S. Pat. No. 5,057,372 discloses the use of various polyolefin based adhesives to coat the entire surface of the protective film layer. PCT/US95/08436 (WO96/01605) and PCT/IB96/01151 (WO97/15446) disclose the use of electron-beam curable adhesives particularly saturated copolyesters with terminal acrylic double bonds.
Accordingly, there remains a need for a system which will provide improved protection to minimize contamination problems of copper foils in the printed circuit board industry while simultaneously overcoming the problems noted above.
SUMMARY OF THE INVENTION
The present invention relates to a protected copper foil laminate comprising (A) a copper foil layer, and (B) a multilayer protective film having an outer surface coated with a silicone polymer release composition which prevents adhesion of the film at high temperature and pressure laminating conditions, and an inner surface adjacent the copper foil layer, said inner surface having disposed uniformly thereon a solution of a pressure sensitive silicone polymer in an organic solvent from which the organic solvent is removed, wherein after exposure of the copper foil laminate to a temperature of at least 300° F. and a pressure of at least 300 psi, none of the pressure sensitive silicone polymer transfers to the copper foil layer.
This invention further relates to a method of protecting a copper foil intended for use in the manufacture of printed circuit boards, by providing a release coating on one side of a polyester film; applying a solution of a pressure sensitive silicone adhesive in an organic solvent to the other side of the polyester film; removing the organic solvent; and laminating a copper foil to the pressure sentitive silicone adhesive side of the polyester film.
Still further, this invention relates to a protected copper foil laminate of a clean copper foil sheet and a protective deep matte polyester film laminated to said copper foil sheet, said film having a smooth side and a rough side and having a uniform layer of a release coating on the entire smooth side and a uniform layer of a pressure sensitive silicone adhesive on the entire rough side, the silicone adhesive being in adhesive contact with the copper foil sheet, wherein no adhesive transfers to the copper foil sheet after exposure of the laminate to a temperature of at least 300° F. and a pressure of at least 300 psi.
REFERENCES:
patent: 4818576 (1989-04-01), Pennace et al.
patent: 5091251 (1992-02-01), Sakumoto et al.
patent: 5120590 (1992-06-01), Savage et al.
patent: 5309925 (1994-05-01), Policastro
patent: 5350621 (1994-09-01), Yuhas et al.
patent: 5413838 (1995-05-01), Azuma et al.
patent: 5562917 (1996-10-01), Durif et al.
Matthes Jurgen
Pasternack Melvin
Jacobs Bruce F.
Moore Margaret G.
Sentrex Company, Inc.
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