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SMT electronics assembly manufacturing forum.

SMT Reflow temp

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SMT Reflow temp | 24 February, 2015

I'm new in this industry and need a little direction. I have a wide verity of SM parts on a board, top and bottom. The larger components have a very nice reflow, good shine. The 0402/0201's has a dull almost cold solder look. The boards function and work properly but I am not satisfied with is look.

I have a Heller 7 zone oven that allows me to make a profile to match the kester solder reflow profile. where should I go for more information to insure a good product.

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SMT Reflow temp | 24 February, 2015

Could you show us the reflow profile and 0402/0201 pictures? I have had the same situation before just because insufficient solder paste ( Specially on 0201) and maybe not enough heat reflow profile.

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SMT Reflow temp | 25 February, 2015

Hi Bartel , 1.1 Profile Solution to Cold Soldering Cause for Cold soldering The peak temp of reflow is too low. The preheating temp is too high and it takes too long Solution Lower the preheating temp and increase the peak temp in the reflow zone

1.2 Profile Solution to Solder Bridges Cause for Solder Bridges The viscosity of melting solder during reflow is high Solder paste collapse during preheating Solution Lower the preheating temp a little and increase the peak temperature 1.3 Profile Solution to Solder Balls Cause for Solder Balls Preheating has not been done properly

Solution Lengthen the time for preheating

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SMT Reflow temp | 11 March, 2015

Small paste deposits have less flux thus less flux activity to enhance the wetting. So preheat needs to be as short as possible, ramp to spike if possible. Try not to ramp hold and spike - pending thermal delta on product can be made to ramp to spike ok without hold phase.

If Paste is T4 or higher, and non N2 reflow, issue is worse as higher metal surface area is involved togather with lower flux amount.

If can increase paste volume with stencil design can try and balance this out a bit.

If have access to N2 reflow this helps greatly as solder paste deposits get smaller.

Of course the solder paste flux has influence one vs another - better activity in smaller amounts , but always trade off - more active flux can be issue in post assembly pending product intended purposes etc

Is all game of compromise.

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SMT Reflow temp | 16 March, 2015

If it took you a long time to get it through pick and place or you had to do a lot of hand add of SMT parts, your paste can start to dry out especially on the small deposits. We've seen this time and time again. We've gotten way better at quickly processing FA's over the years but it used to be a struggle and 1st boards would process very slow.

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SMT Reflow temp | 16 March, 2015

This has been a challenge for most manufacturers. It depends on board thickness, lead or lead free paste/parts. We have a slim-kic to get the profiles correct in our 14 zone oven. I believe it may be the recently posted suggestion of too much heat in beginning zones. Also, it helped that we branched out and found better paste. We use either KOKI or metallic inc. regular no clean in replace of Kester, or AIM lead-free paste. The outcome is a much better finish.

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SMT Reflow temp | 14 April, 2015

Hello Marshall, I represent Metal Etch Services, we manufacture SMT Single and Multi-Level Stencils, we have over 25 years experience and one of the reasons most of our customers like us is because we offer technical assistance. Regarding the issue you are having with 0402 and 0201 components can be caused by factors such as: 1) Wrong solder paste type. 2) Insufficient flux. 3) Wrong profile, etc. If you want, you can send me pictures of this or any other issue you might be having and we can gladly assist you in eliminating them. Please do not hesitate to contact me with any questions. (760) 402-1080

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SMT Reflow temp | 16 April, 2015

Your solder paste manufacturer’s profile is just a “guideline.” You can customize your profile to meet your product’s need.

For better grain-structure (shiney-ness) try a ramp soak spike profile keeping your preheat temps very low before your reflow zone. This preserves the activator in your flux.

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SMT Reflow temp | 28 April, 2015

Is this solder lead or lead free?

Try look at the delta of the PCB during re-flow, you might find that the smaller parts are being "cooked" faster and burning off the flux.

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