Fibrous supported polymer encapsulated electrical component

• US 6,263,158 B1
• Filed: 05/11/1999
• Issued: 07/17/2001
• Est. Priority Date: 05/11/1999
• Status: Active Grant

• Current Assignee: Watlow Electric Manufacturing Company
• Original Assignee: Watlow Polymer Technologies
• Inventors: Rutherford, James M.
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): CAMPBELL, THOR S
• Application Number:
  US09/309,429
• Time in Patent Office: 798 Days
• Field of Search: 219/544, 219/546, 219/548, 219/549, 392/432, 392/434, 392/503, 296/11
• US Class Current: 392/503
• CPC Class Codes: H05B 2203/003 using serpentine layout
• CPC Class Codes: H05B 2203/013 Heaters using resistive films or coatings
• CPC Class Codes: H05B 2203/014 Heaters using resistive wires or cables not provided for in H05B3/54
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 3/36 heating conductor embedded in insulating material
• CPC Class Codes: H05B 3/54 flexible
• CPC Class Codes: H05B 3/56 Heating cables
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673

Abstract

Heating elements, electrical devices and processes for manufacturing these components are provided. The heating elements and electrical components employ a fibrous support layer, such as a non-woven glass mat, which provides structural support to the relatively thin cross-section of the electrical device or resistance wire when a polymeric layer is applied, such as by molding under pressure.

Claims

1. An insulated electrical component comprising:

a. an electrical device having a circuit path portion with a relatively thin cross-section which is susceptible to distortion under molding pressure;

b. a fibrous glass mat support layer being more resistant to distortion under molding pressure than said circuit path portion, disposed over said electrical device and said circuit path portion; and

c. a polymeric layer molded substantially around said fibrous support layer, said electrical device and said circuit path portion whereby said fibrous glass mat support layer provides structural support and distortion resistance to said circuit path portion when said polymeric layer is applied in a mold under pressure.

2. The electrical component of claim 1 wherein said electrical device comprises and electrical resistance heating foil, powder, wire or printed circuit disposed in a looped circuit path.

3. The electrical component of claim 2 wherein said fibrous support glass mat layer comprises a pair of glass mat layers adhered to a top and bottom surface of said electrical resistance heating foil, powder, wire, or printed circuit.

4. The electrical component of claim 1 wherein said polymeric layer comprises a polymer having a melting or degradation temperature greater than about 93°

C.

5. The electrical component of claim 4 wherein said fibrous support glass mat layer is adhered to said electrical device with a low volatile content, thermally conductive adhesive.

6. The electrical component of claim 1 wherein said electrical device comprises one or more of:

an integrated circuit component, an electrical conductor path, a power source or resistance wire.

7. The electrical component of claim 1 wherein said polymeric layer is disposed under a pressure of about 500-4,000 psi through said fibrous support glass mat layer and around said electrical device, without substantially moving or distorting said electrical device relative to said fibrous support glass mat layer.

8. The electrical component of claim 6 wherein said electrical device and said polymeric layer are molded into a unified, hermetic structure.

9. The electrical component of claim 1 wherein said fibrous support glass mat layer comprises a glass mat having cut glass fibers joined together with a resinous adhesive.

10. The electrical component of claim 1 wherein said electrical device comprises an electrical resistance heating wire, said electrical component further comprising a thermostat or thermistor adapted to regulate current through said electrical resistance heating wire upon reaching a preselected temperature limit.

11. A resistance heating element comprising:

a. an electrical resistance heating wire disposed in a circuit path, said wire having a pair of terminal end portions, said electrical resistance heating wire being susceptible to distortion under molding pressure;

b. a pair of electrical conductors fixed to said terminal end portions of said wire;

c. a first glass mat adhered to a top surface of said electrical resistance heating wire;

d. a second glass mat adhered to a bottom surface of said electrical resistance heating wire, said first and second glass mats being more resistant to distortion by molding pressure than said electrical resistance heating wire; and

e. a high temperature polymeric layer molded under a pressure of at least 500 psi substantially around said circuit path and said first and second glass mats, whereby said first and second glass mats assist in thermally insulating a portion of said polymeric layer from said electrical resistance heating member and provide structural support to said electrical resistance heating wire during said molding so as to resist distortion of said electrical resistance heating wire under said molding pressure.

12. The resistance heating element of claim 11 having a power rating of about 5-10,000 W.

13. The heating element of claim 12 wherein said polymeric layer comprises a non-electrically conductive, thermally-conductive additive.

14. The heating element of claim 11 wherein said first and second glass mats are adhered to said electrical resistance heating member by a low volatile constituent containing thermally conductive adhesive.

15. The heating element of claim 14 wherein said adhesive comprises a thermally conductive additive.

16. The heating element of claim 11 wherein said polymeric layer comprises an epoxy resin bonded to said first and second glass mats and electrical resistance heating member.

17. The heating element of claim 16 wherein said first and second glass mats are joined to said electrical resistance heating member by a polymeric adhesive containing the same polymer as said polymeric layer.

18. A method of making an insulated, electrical component, comprising:

providing an electrical device having a relatively thin cross-section portion which is susceptible to being distorted under molding pressure;

adhering said electrical device onto a fibrous glass mat support layer which is less susceptible to being distorted under molding pressure than said relatively this cross-section portion; and

molding said fibrous glass mat support layer and said electrical device within a polymer layer under pressure, whereby said fibrous glass mat support layer provides structural support to said relatively thin cross-section portion of said electrical device so as to resist distortion thereof when said polymer layer is applied.

19. The method of claim 18, wherein said molding step comprises compression molding a polymer preform over and through said fibrous glass mat support layer and over said electrical device to form a hermetic coating which is resistant to delamination.

20. The method of claim 18, wherein said fibrous glass mat support layer comprises a non-woven or woven glass mat, having an air permeability rating of at least about 1,000 cubic feet per minute.

21. The method of claim 19, wherein said electrical device comprises a Ni—

Cr resistance heating wire, and said polymer layer comprises a thermosetting resin.

22. The method of claim 21, wherein said thermosetting resin comprises an non-electrical conducting, thermally conducting additive.

23. The method of claim 19, wherein said polymer preform is subject to heat or pressure or both to substantially become a liquid or semi-liquid for more effectively wetting the surfaces of said fibrous glass mat support layer and said electrical device during said molding step.

24. The method of claim 18, in which said combination of polymer layer and fibrous glass mat support layer has a flexural modulus at least 50% greater than the flexural modulus of said polymer layer, without said fibrous glass mat support layer.

26. The method of claim 24 further comprising liquefying at least a portion of said polymer layers to permit easier penetration of said polymer through said fibrous glass mat support layers.

28. The method of claim 26 wherein said fibrous glass mat support layers help to ballast said element precursor in said molding device during said liquefication step.

25. A method of making an insulated heating element, comprising:

providing an electrical resistance heating wire disposed in a looped circuit path, said wire having a relatively thin cross-section which is susceptible to distortion of its circuit path by movement thereof under a molding pressure;

disposing a pair of open pore, fibrous glass mat support layers on a top and bottom surface of said electrical resistance heating wire, said fibrous glass mat support layer being more resistant to distortion than said electrical resistance heating wire under said molding pressure and being joined to said electrical resistance heating wire to form an element precursor;

inserting said element precursor between a pair of polymer layers in a molding device; and

compression molding said polymer layers and said element precursor to form a substantially hermetic insulating polymeric layer around said circuit path whereby said pair of open pore, fibrous glass mat support layers provide distortion resistance to said electrical resistance heating wire under said molding pressure.

27. The method of claim 25, wherein said liquefication step comprises the use of heat or pressure or both.

29. An insulated electrical component comprising:

a. an electrical device having a thin conductive or semi-conductive portion which is susceptible to distortion under a molding pressure;

b. a support layer joined to said electrical device, said support layer comprising a woven or non-woven, open pore mat which has an air permeability rating of at least about 1,000 cubic feet per minute and a distortion resistance to said molding pressure which is greater than said thin conductive or semi-conductive portion; and

c. a molded polymeric layer disposed around said electrical device and said support layer, whereby said support layer provides distortion resistance for said thin conductive or semi-conductive portion when said polymeric layer is applied in a mold under said molding pressure.