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glue strangeness

Gian.D

#9829

glue strangeness | 2 September, 1999

We are assembling double side pcs reflowing (smt) on top and by wave on bottom. After first step (smt) we dispense glue on the bottom side putting one or two glue dots under small components and we cure in oven before wave. After wave soldering we find some components (sot 89 more or less) lost with their glue and a part of solder resist (exactly the same shape of glue drops) missing (what we see are some small little deep holes). The pads of missing components are correctly covered by solder such that we think to loose them just the boards enter the wave. Is there someone who experieced something like that.I will appreciate any suggestion. Thanks g.d.

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JohnW

#9830

Re: glue strangeness | 2 September, 1999

| We are assembling double side pcs reflowing (smt) on top and by wave on bottom. | After first step (smt) we dispense glue on the bottom side putting one or two glue dots under small components and we cure in oven before wave. | After wave soldering we find some components (sot 89 more or less) lost with their glue and a part of solder resist (exactly the same shape of glue drops) missing (what we see are some small little deep holes). | The pads of missing components are correctly covered by solder such that we think to loose them just the boards enter the wave. | Is there someone who experieced something like that.I will appreciate any suggestion. Thanks | g.d. | | Gian,

sounds like your first thought should be to look at the handling of the boards cos if the glue and component and some resist is missing they're being knocked off somewhere. Is there a depanalisation stage ? how to they get moved round the shop ? Easiest way is to to a bit of house keeping first and clean all the benches your working with then do the run, if there are component's left after it then you've found one of the problems.

JohnW

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Brad Kendall

#9831

Re: glue strangeness | 7 September, 1999

| | We are assembling double side pcs reflowing (smt) on top and by wave on bottom. | | After first step (smt) we dispense glue on the bottom side putting one or two glue dots under small components and we cure in oven before wave. | | After wave soldering we find some components (sot 89 more or less) lost with their glue and a part of solder resist (exactly the same shape of glue drops) missing (what we see are some small little deep holes). | | The pads of missing components are correctly covered by solder such that we think to loose them just the boards enter the wave. | | Is there someone who experieced something like that.I will appreciate any suggestion. Thanks | | g.d. | | | | Gian, | | sounds like your first thought should be to look at the handling of the boards cos if the glue and component and some resist is missing they're being knocked off somewhere. | Is there a depanalisation stage ? how to they get moved round the shop ? | Easiest way is to to a bit of house keeping first and clean all the benches your working with then do the run, if there are component's left after it then you've found one of the problems. | | JohnW | | John is right. If the part is near the edge of the board and you are using board racks, you could be knocking them off. I have seen this many times. If not, the only other explination is the expansion rate on that device must be much different then the board and during preheat they break off. Seems odd, but see if there are parts in the preheat of the wave. If so, try a different dispense pattern.

Brad Kendall

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