Mixed Thixotrope Solder Mask
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
The existing solder mask formulation used on all board products has been found to experience excessive flow during processing. A solder mask applied via the standard wire screen technique has been chemically modified to restrain the excessive flow into its masked area during coating. The reformulated solder mask is as follows: PKHC* 33.5 D.E.N. 439** 45.1 NMA 16.7 Diethyl CARBITOL* 0.11 Paint Additive #3** 0.11 Thixotrope 4.55 CALCOFLUOR*** 0.08 Thixotrope = CAB-O-SIL**** M-5 and 5-50% CAB-O-SIL N-70-TS The use of the hydrophobic silica provides a mask with almost total elimination of flow to less than 0.001 inch; however, this silica prevents leveling of the screened solder mask.