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Improvement of Cleaning Effect of Surface Mount Device by PCB Design

IP.com Disclosure Number: IPCOM000112820D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Ishiguro, M: AUTHOR [+3]

Abstract

This article describes a PCB design for improving cleanability of surface mount devices which do not have standoff. The combination of solder resist and silk-screened paste is used as a standoff for providing a space for cleaning between the device and the card.

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This is the abbreviated version, containing approximately 80% of the total text.

Improvement of Cleaning Effect of Surface Mount Device by PCB Design

      This article describes a PCB design for improving cleanability
of surface mount devices which do not have standoff.  The combination
of solder resist and silk-screened paste is used as a standoff for
providing a space for cleaning between the device and the card.

      Chlorinated hydrocarbon solvents used heretofore to remove
solder flux have to be eliminated because they are substances which
may destroy terrestrial environment.  As an alternative, water
soluble process is desirably used.  However, if water soluble flux is
left between the printed circuit board and the surface mount device,
they may cause corrosion.  Therefore, water soluble flux must be
removed perfectly.

      To remove water soluble flux completely, sufficient space for
cleaning must be assured between the bottom surface of the device and
the top surface of the card but there are many commercial components
without standoff.

This PCB design provides the space for cleaning without component
design change.

      Figures show examples of this PCB design.  Fig. 1 is of
straight bar type.  The combination of two copper lines of straight
bar shape, solder resist deposited on the copper lines and insulating
paste deposited on the solder resist by silk screen provide the space
for cleaning.  As can be seen from Fig. 3, the space for cleaning is
given between the two copper lines.

      Fig. 2 is of round lan...