Claims
- 1. Process for preparing high density para-aramid paper for use in electrical circuit board laminates having low coefficient of thermal expansion comprising the steps of (1) preparing a 0.01 to 3 percent, by weight, aqueous slurry of para-aramid fibers made up of 0-50 volume percent para-aramid pulp and 50-100 volume percent para-aramid floc having lengths of 0.8 to 12.7 mm, (2) forming a sheet from the slurry using known papermaking methods, (3) drying the thusly formed sheet and (4) calendering the sheet in one or more steps between rigid rolls heated to 125.degree. to 400.degree. C. at a pressure of 1500 to 5000 lbs/inch (268 to 894 kg/cm) nip pressure.
- 2. Process of claim 1 wherein preparing the slurry includes adding a binder which consists of 5 to 15 percent, by weight, based on the total solids content of the paper, of a polymeric binder of aramid fibrids.
- 3. Process of claim 1 wherein preparing the slurry includes adding a binder which consists of 5 to 15 percent, by weight, based on the total solids content of the paper, of a water dispersible polymeric binder selected from the group consisting of epoxy resins, phenolic resins, polyester resins, polyureas, polyurethanes, melamine formaldehyde resins and fluorocarbon resins.
- 4. Process of claim 2 wherein the aramid fibrids are poly(m-phenylene isophthalamide) fibrids.
- 5. Electrical circuit board substrate containing at least one layer of the para-aramid paper made by the process of claims 1, 2, or 3, having a volume percent total matrix binder of no more than 52 plus 0.13 times the volume percent para-aramid floc in the para-aramid fibers in the layers, but no less than 15 volume percent total binder.
- 6. The circuit board substrate of claim 5 having 50 to 80 volume percent para-aramid fibers.
- 7. The circuit board substrate of claims 5 or 6 having a volume percent total matrix binder of no more than 42 plus 0.13 times the volume percent para-aramid floc in the para-aramid fibers in the layers.
- 8. Process of claim 1 wherein the para-aramid is poly(p-phenylene terephthalamide).
- 9. Process of claim 2 wherein the para-aramid is poly(p-phenylene terephthalamide).
- 10. Process of claim 3 wherein the para-aramid is poly(p-phenylene terephthalamide).
CROSS-REFERENCE TO RELATED APPLICATION
This is a division of application Ser. No. 775,577, filed 9-17-85, now abandoned, which is a continuation-in-part of U.S. Ser. No. 662,938, filed 10-19-84, now abandoned.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
3756089 |
Gross |
Sep 1973 |
|
4035694 |
Barton et al. |
Jul 1977 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
0128843 |
Dec 1984 |
EPX |
Non-Patent Literature Citations (3)
Entry |
Research Disclosure, No. 188, Item No. 18823, p. 674 (12/79). |
Research Disclosure, No. 190, Item 19037, p. 74 (2/80). |
IBM Technical Disclosure Bulletin, vol. 20, No. 2, p. 555 (7/77). |
Divisions (1)
|
Number |
Date |
Country |
Parent |
775577 |
Sep 1985 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
662938 |
Oct 1984 |
|