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id m0u6HYV-00007jC; Mon, 8 Apr 96 09:04 CDT |
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08 Apr 96 10:07:58 EDT |
| From [log in to unmask] Mon Apr 8 09: |
43:11 1996 |
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As has been stated the effect is due to hole to lead ratio as a basic guide the
hole to lead ratio is calculated from the lead and is the lead size plus 0.010"
plus any tolerance. This ia requirement for auto insertion not soldering. The
sunken joint is also caused by outgassing when it appears on the base of the
board. If the outgassing occurs as the board exits the wave either a pin hole or
a sunken joint will occur.
Mounting parts flush to the board surface without any stand off from the board
also causes blow back which looks like outgassing but it is not the printed
board. Flux vapour do not escape through the board due to the component body
masking the top of the hole.
Check out my DFM video tape on the home page it has all the good design rules
for assembly and soldering.
Have A Great Day.
Our Home Page solves your SMT process Problems
Bob Willis
Electronic Presentation Services
2 Fourth Avenue, Chelmsford, Essex CM1 4HA. England.
Tel: (44) 01245 351502
Fax: (44) 01245 496123
Home Page: http://ourworld.compuserve.com/homepages/bwillis
Email: [log in to unmask]
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