Solder resist paste and method of soldering

• US 4,634,039 A
• Filed: 10/19/1984
• Issued: 01/06/1987
• Est. Priority Date: 10/19/1984
• Status: Expired due to Term

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Banerjee, Hari N.
• Primary Examiner(s): Ramsey, Kenneth J.
• Assistant Examiner(s): McKee, Christopher L.
• Application Number:
  US06/662,916
• Time in Patent Office: 809 Days
• Field of Search: 228/118, 228/215, 106/2, 427/259
• US Class Current: 228/118
• CPC Class Codes: B23K 35/224 Anti-weld compositions; Braze stop-off compositions
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2203/0591 Organic non-polymeric coating, e.g. for inhibiting corrosion thereby preserving solderability
• CPC Class Codes: H05K 2203/0769 Dissolving insulating materials, e.g. coatings, not used for developing resist after exposure
• CPC Class Codes: H05K 2203/0783 Using solvent, e.g. for cleaning; Regulating solvent content of pastes or coatings for adjusting the viscosity
• CPC Class Codes: H05K 3/0076 characterised by the composition of the mask
• CPC Class Codes: H05K 3/0094 Filling or covering plated through-holes or blind plated vias, e.g. for masking or for mechanical reinforcement
• CPC Class Codes: H05K 3/3452 Solder masks

Abstract

A solder resist paste having the feature that it is relatively easily removed is disclosed. The paste is comprised of a liquid polyglycol (e.g. Pluronic 25R2 by BASF) and either Kaoline or talc powder. In operation, the paste is selectively applied to holes in the PCB which it is desired to keep open during a soldering process. The paste is then washed out of the holes, additional components mounted via those holes, and soldered into place.

Claims

1. A method of soldering components to a PCB (printed circuit board), said method characterized by:

selectively applying a temporary solder resist consisting of a polyglycol and either kaolin or talc powder to at least one hole in said PCB;

selectively situating first components on said PCB either on the surface of said PCB or into holes other than the holes containing said solder resist;

soldering said first components to said PCB;

washing said PCB with a solvent in which said solder resist is soluble and which is not harmful to either said PCB or said first components;

selectively situating second components on said PCB employing holes that had previously held said solder resist; and

soldering said second components to said PCB.

2. The method of claim 1 wherein said polyglycol is a nonionic surfactant polyol.