Protected conductive foil assemblage and procedure for preparing same using static electrical forces

• US 5,167,997 A
• Filed: 03/29/1990
• Issued: 12/01/1992
• Est. Priority Date: 05/05/1989
• Status: Expired due to Term

• Current Assignee: Nikko Materials USA, Inc. (Eternal Materials Co., Ltd.)
• Original Assignee: Gould, Inc. (Transdigm Group Incorporated)
• Inventors: Burgess, David P., Callahan, John P., Chamberlain, Jamie H., Savage, Rolland D.
• Primary Examiner(s): Ryan, Patrick J.
• Application Number:
  US07/501,093
• Time in Patent Office: 978 Days
• Field of Search: 428/76, 428/409, 428/457, 428/461, 428/480, 428/901, 156/60, 29/900
• US Class Current: 428/76
• CPC Class Codes: B32B 2310/025 Electrostatic charges
• CPC Class Codes: B32B 2311/12 Copper
• CPC Class Codes: B32B 2367/00 Polyesters, e.g. PET, i.e. polyethylene terephthalate
• CPC Class Codes: B32B 2457/08 PCBs, i.e. printed circuit boards
• CPC Class Codes: B32B 37/00 Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
• CPC Class Codes: B32B 37/0007 involving treatment or provisions in order to avoid deformation or air inclusion, e.g. to improve surface quality
• CPC Class Codes: B32B 7/06 permitting easy separation
• CPC Class Codes: H05K 3/022 Processes for manufacturing precursors of printed circuits, i.e. copper-clad substrates
• CPC Class Codes: H05K 3/025 by transfer of thin metal foil formed on a temporary carrier, e.g. peel-apart copper
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 428/239 Complete cover or casing
• CPC Class Codes: Y10T 428/31 Surface property or characteristic of web, sheet or block
• CPC Class Codes: Y10T 428/31678 Of metal
• CPC Class Codes: Y10T 428/31692 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

A conductive copper foil for use in preparing printed circuit boards is protected from damage during storage, shipment and further processing by covering at least one side of the foil with a sheet of plastic film. The film is removably joined with the foil as a result of the essential absence of gaseous material between the film and the foil. Thus, the film conforms intimately to the contours and shape of the foil surface and clings tightly thereto to permit movement and further processing of the foil with the film adhering tightly thereto. The absence of air between the film and the foil is produced by oppositely statically electrically charging the film and the foil such that they are forced together sufficiently to squeeze the air out from therebetween. The film is selected to be sufficiently resistant to laminating temperature and pressure conditions so as to remain in its covering, protecting relationship to the foil and avoid sticking to the laminating press plate and retain its removability from the foil after lamination.

Claims

1. A protected conductive foil assemblage comprising:

a conductive metallic foil having two sides, one side of the foil being adapted for bonding to a dielectric support during a lamination process involving pressing between plates of a laminating press; and

a dielectric plastic film layer overlying the other side of the foil in covering, protecting relationship thereto,

there being an essential absence of gaseous material between the plastic film layer and said other side of the foil, whereby the plastic film layer conforms intimately to the contours and shape of the other side of the foil and clings tightly thereto to permit movement and further processing of the foil with the film layer remaining in said covering, protecting relationship to said other side of the foil, said plastic film layer being removable from the foil by peeling,

said plastic film being sufficiently resistant to the temperature and pressure conditions encountered during a lamination process to avoid sticking to a laminating press plate and to retain its removability from the other side of the foil after lamination of the foil to a dielectric support.

2. A protected film assemblage as set forth in claim 1, wherein said foil is an electrodeposited foil having a matte side and a shiny side, said one side being the matte side and said other side being the shiny side.

3. A protected foil assemblage as set forth in claim 2, wherein said shiny side has been treated for enhanced lamination bond strength between the shiny side and a dielectric support and said plastic film is removable after laminating without disturbing said treatment.

4. A protected foil assemblage as set forth in claim 3, wherein said plastic film layer is sufficiently transparent to permit visual inspection of the treatment on the shiny side of the metallic foil while said film layer is in said covering, protecting relationship thereto.

5. A protected foil assemblage as set forth in claim 1, wherein said plastic film layer is sufficiently transparent to permit visual inspection of the other side of the metallic foil while said film layer is in said covering, protecting relationship thereto.

6. A protected foil assemblage as set forth in claim 1, wherein said foil and said film layer are in the form of webs and are wound up together in the form of a roll.

7. A protected foil assemblage as set forth in claim 1, wherein said foil and said plastic film layer are coextensive in size and said assemblage includes a coextensively sized dielectric support layer containing a curable laminating resin disposed against said one side of the foil.

8. A protected foil assemblage as set forth in claim 1, wherein said plastic film layer has a thickness in the range of from about 0.5 mil to about 5.0 mils.

9. A protected foil assemblage as set forth in claim 8, wherein said plastic film layer has a thickness of about 2.0 mils or less.

10. A protected foil assemblage as set forth in claim 1, wherein said plastic film layer is capable of being exposed to the conditions encountered in a laminating press without releasing chemicals which contaminate the foil.

11. A protected foil assemblage as set forth in claim 1, wherein said foil comprises copper.

12. A protected assemblage as set forth in claim 11, wherein said plastic film comprises a polyester.

13. A protected assemblage as set forth in claim 12, wherein said polyester comprises a polyethylene terphthalate.

14. A protected assemblage as set forth in claim 1, wherein said plastic film layer comprises a polyester.

15. A protected assemblage as set forth in claim 14, wherein said polyester comprises a polyethylene terphthalate.

16. A procedure for protecting an electrodeposited conductive metallic foil during further processing comprising:

providing a piece of conductive foil having two sides, one side of the foil being adapted for bonding to a dielectric support by a lamination process involving pressing between plates of a laminating press;

providing a layer of dielectric plastic film;

placing said layer of film over the other side of said piece of metallic foil in covering, protecting relationship to said other side; and

forcing said layer of film and said foil together by applying thereto an evenly distributed force pattern to drive gaseous material out from between the film and the other side of the foil and produce an essential absence of gaseous material between the film and the other side of the foil, whereby the plastic film layer conforms intimately to the contours and shape of the other side of the foil and clings tightly thereto to permit movement and further processing of the foil with the film layer remaining in said covering, protecting relationship to said other side of the foil, said plastic film layer being removable from the foil by peeling,

said plastic film being sufficiently resistant to the temperature and pressure conditions encountered during a lamination process to avoid sticking to a laminating press plate and to retain its removability from the other side of the foil after lamination of the foil to a dielectric support.

17. A procedure as set forth in claim 16, wherein said evenly distributed force pattern is created by oppositely static electrically charging said film and said foil.

18. A procedure for releasably joining a protective, covering layer of dielectric film to one side of a conductive metallic foil adapted for being bonded to a dielectric support during a lamination process, said procedure comprising the steps of:

providing a piece of conductive foil having two sides, one side of the foil being adapted for bonding to a dielectric support by a lamination process involving pressing between plates of a laminating press;

providing a layer of dielectric film which is sufficiently resistant to the temperature and pressure conditions encountered during a lamination process to avoid sticking to a laminating press plate or to a piece of foil after exposure to laminating conditions;

placing said layer of film over the other side of said piece of foil in a covering, protecting relationship thereto; and

oppositely static electrically charging said film and said foil to cause said film and said foil to be attracted to one another to thereby drive gaseous material out from between the film and the other side of the foil and produce an essential absence of gaseous material between the film and the other side of the foil, whereby the plastic film layer conforms intimately to the contours and shape of the other side of the foil and clings tightly thereto to permit movement and further processing of the foil with the film layer remaining in said covering, protecting relationship to said other side of the foil, said plastic film layer being removable from the foil by peeling.

19. A procedure as set forth in claim 18, wherein the static electrical charges on said film and on said foil are evenly distributed over the respective surfaces thereof whereby the film and the foil are attracted together by an evenly distributed force pattern.

20. A procedure as set forth in claim 19, wherein said charging step includes passing said foil with the film thereon through an electrical gradient field.

21. A procedure as set forth in claim 20, wherein said electrical gradient field is established by providing a positively charged generally straight conductive wire electrode and causing said foil to be a negatively charged electrode, said wire being positioned in laterally spaced, generally parallel relationship relative to the major plane of the foil, said foil with the film thereon being moved in a direction which is generally parallel to the plane of the foil and which is generally transverse relative to the longitudinal axis of said wire, said film being positioned between the wire and the foil during said movement thereof.

22. A procedure as set forth in claim 21, wherein said foil is in conductive contact with the surface of a rotating, conductive, negatively charged roller during said movement of the foil with the film thereon.

23. A procedure as set forth in claim 22, wherein said roller is arranged for rotation about an axis that is generally parallel to the longitudinal axis of said wire.

24. A procedure as set forth in claim 21, wherein said wire has a diameter of approximately 0.008 inches.

25. A procedure as set forth in claim 21, wherein said wire is formed from stainless steel.

26. A procedure as set forth in claim 21, wherein the lateral gap between said wire and said foil is approximately 3/8 inch.

27. A procedure as set forth in claim 21, wherein a voltage potential of 15 kV is applied between said wire and said foil.

28. A procedure as set forth in claim 23, wherein said wire is formed from stainless steel and has a diameter of about 0.008 inches, wherein the gap between said wire and said roller is approximately 3/8 inches, and wherein a voltage potential of about 15 kV is applied between said roller and said wire.

29. A procedure as set forth in claim 20 wherein is included the step of causing said film to be brought into contact with a grounding element after said foil with the film thereon have been passed through the electrical gradient field.

30. A procedure as set forth in claim 21, wherein is included the step of providing an elongated static grounding element disposed in laterally spaced, generally parallel relationship relative to said wire, said element being located in a position for contacting and grounding said foil after the foil and the film have moved through said field.

31. A procedure as set forth in claim 30, wherein said element is positioned for simultaneously contacting the entire lateral extent of said film as the latter is moved in said direction.

32. A protected conductive foil laminate comprising:

a conductive metallic foil having two sides;

a plastic film layer overlying one side of the foil in covering, protecting relationship thereto; and

a dielectric support bound to the other side of the foil as a result of having undergone a lamination process involving pressing between plates of a laminating press,

there being an essential absence of gaseous material between the plastic film layer and said other side of the foil, whereby the plastic film layer conforms intimately to the contours and shape of the other side of the foil an clings tightly thereto to permit movement and further processing of the foil with the film layer remaining in said covering, protecting relationship to said other side of the foil, said plastic film layer being removable from the foil by peeling,

said plastic film being characterized as having initially been sufficiently resistant to the temperature and pressure conditions encountered during the lamination process to avoid sticking to a laminating press plate and to retain its removability from the other side of the foil after lamination of the foil to said dielectric support.

33. A protected foil laminate as set forth in claim 32, wherein said foil is an electrodeposited foil having a matte side and a shiny side, said one side being the matte side and said other side being the shiny side.

34. A protected foil laminate as set forth in claim 33, wherein said shiny side has been treated for enhanced lamination bond strength between the shiny side and a second dielectric support and said plastic film is removable without disturbing said treatment.

35. A protected foil laminate as set forth in claim 34, wherein said plastic film layer is sufficiently transparent to permit visual inspection of the shiny side of the metallic foil and the treatment thereon while said film layer is in said covering, protecting relationship thereto.

36. A protected foil laminate as set forth in claim 32, wherein said plastic film layer is sufficiently transparent to permit visual inspection of the other side of the metallic foil while said film layer is in said covering, protecting relationship thereto.