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SMT components Fall Off

Sergio Luiz Vito

#11048

SMT components Fall Off | 14 June, 1999

I am looking for more information about:

1) What kind of evaluation can I do to measure the resistance to fall off of a bottom side glueded SMT component?;

2) There is some influence of doble wave solder machine (temperature, flux, etc) in SMDs fall off ;

3) what are the most importants factors to be controled in assembly process to improve process quality (like SMDs Fall Off);

Best regards

Eng. Sergio Luiz Vito process Dept. from Intelbras

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JohnW

#11049

Re: SMT components Fall Off | 14 June, 1999

| I am looking for more information about: | | 1) What kind of evaluation can I do to measure the resistance to fall off of a bottom side glueded SMT component?; | | 2) There is some influence of doble wave solder machine (temperature, flux, etc) in SMDs fall off ; | | 3) what are the most importants factors to be controled in assembly process to improve process quality (like SMDs Fall Off); | | Best regards | | Eng. Sergio Luiz Vito | process Dept. from Intelbras | Sergio,

The basic test for checking the bottomside glued components is normally a torque test. You can buy the tool from most material supplier's of glue. What your doing is finding the shearing force required to knock a component off. Component's missing from the bottom side of a board are normally due to 1 of 2 things. 1. Insufficient glue to hold the component in place, if your using a dispensing method like a Fuji GL you can up the pressure or rather time for the gule dot being applied and monitor whether they are falling off. An interesting thing to do is note whether they are a) all falling off in the same area, b) random but of the same type or c)completely random. If they are in the same area all the time you may have a board support problem or something is knocking them off - are they there at the end of the smt run?? is there breakout on the card and is the breakout tool doing the damage, if it's random around the board but the same type you might want to look at the finish of the component as it may be too glassy to allow the glue to adhere to it. If it's c) completely random then your into the 2nd category of why part's fall off.. 2) HANDLING! Poor handling processes or lack of concentration by the operators is a problem that can come and go and be really frustraiting in screwing it down. By far the best course of action ( and 1 I've done a fair few times) is walk the boards thro' ( or a sample batch) the entire process checking at which point stuff is falling off. Make your self visible for the first couple of run's ..monitor the process then 'lurk around' out the way for the next couple and see if people handle the stuff differently. It's a bit of a shame that you have to do this but people work differently if they know they are being observed..something I learned quickly while doing time & motion studies..urrgh! Anyway's, in theory the double wave shouldn't be enough to knock anything off the boards. Now that said, it's not imposible but I'd say unlikely, first step is to prove that all the bit's are getting there first.

JohnW

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C. Cross

#11050

Re: SMT components Fall Off | 15 June, 1999

| I am looking for more information about: | | 1) What kind of evaluation can I do to measure the resistance to fall off of a bottom side glueded SMT component?; | | 2) There is some influence of doble wave solder machine (temperature, flux, etc) in SMDs fall off ; | | 3) what are the most importants factors to be controled in assembly process to improve process quality (like SMDs Fall Off); | | Best regards | | Eng. Sergio Luiz Vito | process Dept. from Intelbras | Does your adhesive(glue) require curing? If so, are your temperature and time requirements being met. Also what SMDs are falling off ICs or passives? We have found that the dispense pattern for larger components is critical and requires some trial and error to get it right.

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