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SMT electronics assembly manufacturing forum.


Weights during reflow?

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#79178

Weights during reflow? | 11 October, 2017

We are using a connector on an assy whereby every now and again its raising up on one corner, we have been advised we should weigh them down to ensure flatness, this is the 1st time I've come across having to weigh anything down at SMT reflow? Any advise?

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#79179

Weights during reflow? | 11 October, 2017

It obviously isn't recommended but I've had aluminium blocks milled out to fit over & weigh down connectors in a previous company when using vapour phase reflow. I guess the same will work in a convection oven as well. You will have to adjust your profile to compensate, as well as properly investigate why they aren't staying flat during reflow.

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#79180

Weights during reflow? | 11 October, 2017

Absolutely use aluminum. I have done it to keep a huge board flat after reflow.

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#79181

Weights during reflow? | 11 October, 2017

I've never seen this Can you post picture? aluminum may sink heat and shadow component if too big

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#79187

Weights during reflow? | 11 October, 2017

I've used plenty of weights in the wave solder process, but not in the SMT reflow process. Ask yourself some why's.... such as why is the part lifting at one end? (board bowing possibly), why? Not the correct tg material or issue with oven profile? Why?... etc. I'm sure if you dig deep enough you can find a root cause and potentially a fix without having to use any weights.. I personally don't like the idea of weights in the SMT process since I would be concerned with the solder connections if too much weight was used. I would look at SMT reflow pallets before using weights. There are some really good outfits out there that could make a fixture to hold just about anything in place...

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