Metal-clad dielectric sheeting

• US 4,035,694 A
• Filed: 05/14/1975
• Issued: 07/12/1977
• Est. Priority Date: 01/07/1974
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Groff, Gaylord L., Barton, Robert W.
• Primary Examiner(s): Bell, James J.
• Application Number:
  US05/577,444
• Time in Patent Office: 790 Days
• Field of Search: 174/68.5, 428/215, 428/212, 428/288, 428/297, 428/303, 428/474, 428/480, 428/901, 361/400
• US Class Current: 361/760
• CPC Class Codes: D04H 1/64 the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 2201/0145 Polyester, e.g. polyethylene terephthalate [PET], polyethylene naphthalate [PEN]
• CPC Class Codes: H05K 2201/0278 Polymeric fibers
• CPC Class Codes: H05K 2201/0293 Non-woven fibrous reinforcement
• CPC Class Codes: H05K 2201/0355 Metal foils
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/24967 Absolute thicknesses specified
• CPC Class Codes: Y10T 428/31736 Next to polyester
• CPC Class Codes: Y10T 428/3175 Next to addition polymer from unsaturated monomer[s]
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31797 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 442/656 Preformed metallic film or foil or sheet [film or foil or sheet had structural integrity prior to association with the nonwoven fabric]
• CPC Class Codes: Y10T 442/692 Containing at least two chemically different strand or fiber materials

Abstract

Metal-clad dielectric sheeting useful in the manufacture of printed circuitry comprising an electrically conductive metallic layer adhered to a nonwoven web that comprises a unique fiber blend compacted and held together by a polymeric binder material. The fiber blend includes heat-resistant fibers (preferably aromatic polyamide fibers) and high-tensile-strength fibers that absorb little moisture (preferably polyester fibers); and the amount of fibers that absorb moisture is held to a low amount.

Claims

1. Metal-clad dielectric sheeting useful in the manufacture of printed circuitry comprising a nonwoven web and an electrically conductive metallic layer adhered to at least one side of the web;

said web comprising at least 10 pounds per ream of a fiber blend that comprises high-tensile-strength and heat-resistant discontinuous fibers compacted and held together with a matrix of film-forming polymeric binder material that accounts for 5 to 75 weight-percent of the web;

substantially all of said fibers having a softening point above 450°

F.;

at least 5 weight-percent of the fibers resisting distortion when exposed for 10 seconds to a molten solder bath heated to 500°

F., at least 30 weight-percent of the fibers exhibiting a tensile elongation of at least 20 percent and a tenacity of at least 3.5 grams/denier, and at least 40 weight-percent of the fibers exhibiting a moisture regain of less than about 3 weight-percent; and

the polymeric binder material being solid and nontacky at room temperature, at least initially softening and flowing slightly under the heat and pressure of the compacting operation, and in film form being foldable upon itself without cracking and resisting distortion when heated for 10 seconds on a molten solder bath heated to 500°

F.; and

the metal-clad dielectric sheeting exhibiting no more than a 2 mil/inch change in dimensions upon etch-removal of part or all of the electrically conductive layer, and exhibiting no more than a 10 mil/inch change in dimensions and substantially no blistering when exposed for 10 seconds to a molten solder bath heated to 450°

F.

2. Sheeting of claim 1 in which between 30 and 95 weight-percent of the fiber blend is drawn polyester fibers, between 5 and 60 weight-percent of the fiber blend is aromatic polyamide fibers that resist distortion when exposed for 10 seconds to a molten solder bath heated to 500°

F., and up to 70 weight-percent of the fiber blend is acrylic fibers that resist distortion when exposed for 10 seconds to a molten solder bath heated to 500°

F.

3. Sheeting of claim 2 in which said aromatic polyamide fibers comprise poly(p-phenylene terephthalamide) fibers.

4. Sheeting of claim 2 in which about 80 weight-percent of the fiber blend is said drawn polyester fibers and about 20 weight-percent of the fiber blend is said aromatic polyamide staple fibers.

5. Sheeting of claim 1 in which said polymeric binder material comprises an acrylic-based binder material.

6. Sheeting of claim 1 in which said polymeric binder material is crosslinked.

7. Sheeting of claim 1 in which the conductive layer comprises copper.

8. Sheeting of claim 1 in which the electrically conductive layer is smaller in area than the nonwoven web.

9. Sheeting of claim 8 in combination with electrical components that are electrically connected to the electrically conductive layer.

10. Metal-clad dielectric sheeting useful in the manufacture of printed circuitry comprising a nonwoven web that is less than about 20 mils in thickness and is at least as flexible as a 10-mil-thick biaxially oriented polyethylene terephthalate film and an electrically conductive metallic layer adhered to at least one side of the web;

said web comprising at least 10 pounds per ream of a fiber blend that comprises high-tensile-strength and heat-resistant discontinuous fibers compacted and held together with a matrix of film-forming crosslinked polymeric binder material that accounts for 5 to 75 weight-percent of the web;

substantially all of said fibers having a softening point above 450°

F.;

between 30 and 95 weight-percent of the fibers being drawn polyester fibers, between 5 and 60 weight-percent of the fibers being aromatic polyamide staple fibers, and up to 70 weight-percent of the fiber blend being acrylic fibers;

both the aromatic and acrylic fibers resisting distortion when exposed for 10 seconds to a molten solder bath heated to 500°

F., and the polymeric binder material being solid and nontacky at room temperature, at least initially softening and flowing slightly under the heat and pressure of the compacting operation, and in film form being foldable upon itself without cracking and resisting distortion when heated for 10 seconds on a molten solder bath heated to 500°

F.; and

the metal-clad dielectric sheeting exhibiting no more than a 2 mil/inch change in dimensions upon etch-removal of part or all of the electrically conductive layer, and exhibiting no more than a 10 mil/inch change in dimensions and substantially no blistering when exposed for 10 seconds to a molten solder bath heated to 450°

F.

11. Sheeting of claim 10 in which said aromatic polyamide fibers comprise poly (p-phenylene terephthalamide) fibers.

12. Sheeting of claim 10 in which said polymeric binder material comprises an acrylic-based binder material.

13. Sheeting of claim 11 in which the binder material is an acrylic-based material.

14. Sheeting of claim 10 in which about 80 weight-percent of the fiber blend is drawn polyester fibers and about 20 weight-percent of the fiber blend is aromatic polyamide fibers.

15. Sheeting of claim 10 in combination with electrical components that are electrically connected to the electrically conductive layer.

16. A nonwoven web useful as a dielectric backing for flexible printed circuitry comprising a fiber blend that comprises high-tensile-strength and heat-resistant discontinuous staple fibers that substantially all have a softening point above 450°

F. compacted and held together with a crosslinked film-forming polymeric binder material;

the fibers being present in an amount of at least 10 pounds per ream and the binder material being present in an amount of 5 to 75 weight-percent of the web;

between 30 and 95 weight-percent of the fiber blend being drawn polyester fibers, between 5 and 60 weight-percent of the fiber blend being aromatic polyamide staple fibers, and up to 70 weight-percent of the fiber blend being acrylic fibers;

both the aromatic polyamide and acrylic fibers resisting distortion when exposed for 10 seconds to a molten solder bath heated to 500°

F.;

the polymeric binder material being solid and nontacky at room temperature, at least initially softening and flowing slightly under the heat and pressure of the compacting operation, and in film form being foldable upon itself without cracking and resisting distortion when heated for 10 seconds in a molten solder bath heated to 500°

F.; and

the web upon lamination to an electrically conductive metallic layer forming a metal-clad dielectric sheeting that exhibits less than a 2 mil/inch change in dimensions upon etch-removal of part or all of the electrically conductive layer, and less than a 10 mil/inch change in dimensions and substantially no blistering when exposed for 10 seconds to a molten solder bath heated to 450°

F.