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Guide Rollers for Solder Coating Printed Circuit Boards

IP.com Disclosure Number: IPCOM000113435D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Annabel, SS: AUTHOR [+8]

Abstract

Disclosed here is a method that helps to stabilize the gap between the air knives and the panel surface for solder coating processes. This is a primary factor affecting the uniformity of the solder thickness that is deposited onto the copper surfaces.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Guide Rollers for Solder Coating Printed Circuit Boards

      Disclosed here is a method that helps to stabilize the gap
between the air knives and the panel surface for solder coating
processes.  This is a primary factor affecting the uniformity of the
solder thickness that is deposited onto the copper surfaces.

      One popular way of preparing printed circuit boards for
subsequent assembly/component mounting operations is to put a thin
coating of solder over all the exposed copper surfaces with a process
known as Hot Air Solder Level (HASL).  The panels are dipped
vertically into a large, molten solder pot and then, as they are
removed from the pot, pass thru a set of high pressure air knives
which blow off all the excess solder from the holes and surfaces.

      The narrow gap of the air knives and the air pressure applied
to them, creates a high velocity of air impinging on the panel
surfaces.  Furthermore, the front/rear air knives must be offset
slightly in order to remove the solder effectively from the
thru-holes in the circuit boards.  Thus, as the panel moves
vertically it is driven in opposite directions by these forces.
Variations in the board dimensions may further intensify movement
which will induce even greater differences in the resulting solder
thickness distribution.

      The addition of multiple rollers directly above the air
blow-off knives prevents the panels from oscillating excessively as
they are withdrawn from the solder p...