Patrick Ducas wrote: > > Tom, just a easy one, what type of tool do you use to measure the thickness > of solder? Is it accurate for that specific application? If you know some > tools that should be enough accurate, any hint would be appreciated. > > Thanks in advance > > > > > Don: > > The thickness of solder from a solder level operation > > is dependent upon pad geometry, amongst other things. Board > > fabbers walk the tightrope between blowing enough solder out > > of the holes yet leaving enough remaining on the surface > > mount pads. > > I would strongly urge you to specify a horizontal HASL > > process from your board vendors. Boards should also be > > cocked at a 45 degree angle when going into the solder to > > offset a "north-south, east-west" bias on QFPS. > > Getting back to the pad geometry, the larger the pad, > > the thinner the solder coat is apt to be, because the solder > > has a larger surface over which to retreat. Worst case > > would probably be discrete pads, where we have a stated > > minimum of 50 microinches at the pad center. Maximum solder > > thickness can be held to .0015". > > Where the solder is measured is another issue. We > > always ask our customers to measure from the pad centroid so > > that outgoing and incoming measurements are apples and > > apples. The pad center may or may not be the crest, and it > > usually isn't. When I see thicknesses called out in specs > > that say "as measured at the crest", I chuckle because it > > would take too long just to find the crest of a given pad. > > In all cases, your board fabricator should guarantee > > solderability. > > In summary, the most workable callout would be a solder > > thickness of .0001" nominal, .00005" minimum, .0015" maximum > > (all measurements taken at pad center). Again, > > solderability is to be guaranteed. > > Regards, > > Tom Coyle > > Field Services Engineer > > HADCO Corporation > > > >*************************************************************************** > >* TechNet mail list is provided as a service by IPC using SmartList v3.05 * > >*************************************************************************** > >* To subscribe/unsubscribe send a message <to: [log in to unmask]> * > >* with <subject: subscribe/unsubscribe> and no text in the body. * > >*************************************************************************** > >* If you are having a problem with the IPC TechNet forum please contact * > >* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * > >*************************************************************************** > > > > > > > ------------------------------------------------- > Patrick Ducas > Process Quality Engineer > Matrox Electronic Systems Ltd > E-mail: [log in to unmask] > Tél:(514)969-6000 ext.2971 Fax:(514)685-3415 > ------------------------------------------------- > > > *************************************************************************** > * TechNet mail list is provided as a service by IPC using SmartList v3.05 * > *************************************************************************** > * To subscribe/unsubscribe send a message <to: [log in to unmask]> * > * with <subject: subscribe/unsubscribe> and no text in the body. * > *************************************************************************** > * If you are having a problem with the IPC TechNet forum please contact * > * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * > *************************************************************************** Hi,TechNetters, Patrick asked Tom how he measures the solder thickness on SMT pads. I measure the thickness with X-Ray,which gives me the following opportunities: 1:I can perform several measurements on the same pad. 2:I see WHERE I measure,and usually I find the crest-don't ask me how much time it takes. 3:I can determine also the composition of the solder. Tom's suggestion about 45 degrees is very correct, I think, I have seen differences of 40 micrometers or more between N-S and E-W. Here my experience ends,and because there is always Dave,I will also ask one question: Why do I get different Tin content levels on the same board,depending on the solder thickness I found? In the range of ~1micrometer I get higher readings,although the alloy is "recognizable". Is it a calibration error, the real thing, or me? Bye Gaby *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************