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Reflow soldering issue

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Hi everybody, please advise in case of soldering problems a... - Aug 24, 2018 by PeterC  

#80953

Reflow soldering issue | 24 August, 2018

Hi everybody, please advise in case of soldering problems after the reflow soldering. The problem occurs randomly at different locations on different PCB's (not the complete surface of the board). These places are very difficult for rework. Could you please advise me where to look for a problem? Problem with a PCB producer or a profile problem?

Solder paste is SAC(SnAg3Cu0.5) S3X58-M406 KOKI, surface finishes HASL, profile in the attachment.

Thanks a lot for any advice! Peter.

Attachments:

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#80956

Reflow soldering issue | 24 August, 2018

My first guess at the cause of your components skewing -- Termination pads on the board to not well match the the soldered terminals on the components, causing unbalanced wetting forces on the component terminations while the solder is molten.

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#80957

Reflow soldering issue | 24 August, 2018

Hello davef, thank you for your reply. What do you think about the footprint for the diode on the first picture where the component is not assembled? There is good wetting on one pad of footprint and the other pad has bad wetting. This problem is not always in the same places. It appears on different types of PCB always in different places and not on each PCB. It's a random process.

It is strange that the solder is melted and attached to the component leads and pads are not wetted. Can it mean PCB pads contamination? Or it's a problem of reflow profile?

Thanks a lot!

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#80958

Reflow soldering issue | 24 August, 2018

To my mind, the solder paste has clearly melted, but your HASL plating has not. This with your profile seems to suggest there's something a little weird about your PCB. However, there are probably still questions we could ask - have you successfully run boards on this profile in this oven before. Have all the PCBs with issues come from the same supplier. How have the boards been stored, are they new or old etc..

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#80959

Reflow soldering issue | 24 August, 2018

Could be ...

Consider this: The LED and the BIG pad reflowed before the small pad. The superior force of the solder on the BIG pad pulled the LED over and the LED took the solder on the little pad along with it.

Try this: Print paste on a board. No components. Reflow it. Assess ... This will help you get at board quality issues

Taking a step backwards, if you're concerned about different pads not wetting well ... + Do they take solder in Touch? + Can you increase the soak in reflow to improve this? * Does a different solder paste help?

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#80960

Reflow soldering issue | 24 August, 2018

Hello, I have been using this reflow and reflow profile for the last four months. This problem occurs sporadically. Perhaps 95% of produced PCBs are good, without problem. We order PCB's from a Chinese supplier in smaller batches that we use right now in production. The problem may be in the packaging. They come to us in plastic packages without any desiccants. We have PCB's from two different suppliers. The problem occurs only on the PCB's from one supplier, but not on all PCB's and not on all types of PCB's.

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#80961

Reflow soldering issue | 24 August, 2018

Dear davef, but this LED is skip component, that's a blank footprint and one of its pad is badly wetted...this is the reason for my thinking about contamination.

Do you mean different solder paste with more aggressive flux?

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#80964

Reflow soldering issue | 25 August, 2018

I think if you're having this problem with one supplier and not the other, then you should start there. Work with that supplier to make things correct.

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#80975

Reflow soldering issue | 30 August, 2018

We all agree that you have a PCB issue. It would be for the best if you use a lab to investigate a few of these PCBs. It would be interesting to investigate the plating specs and contamination levels. For a start you should insist on proper packaging of the bare PCBs from your vendor.

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ben

#80977

Reflow soldering issue | 30 August, 2018

Don't search in your profile or your process. The problem is the PCB!

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#80978

Reflow soldering issue | 30 August, 2018

What if you were this guy [PeteC] and you knew this batch of boards had some goofball issue that messed with product quality, increased rework and all that AND you still had to run them?

I've had to eat from the pie before. I'll bet you have also. What should PeteC do to recover?

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#80979

Reflow soldering issue | 30 August, 2018

First suspect PCB contamination - clean the boards, bake/dry them, try again.

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#80986

Reflow soldering issue | 31 August, 2018

Hello guys, first of all I would like to thanks everyone for their posts. I really appreciate it. We are now communicating with vendors about damaged boards. And something about the analysis of damaged boards. We have not yet done, but we are trying to ensure some tests on near university labs. Thanks a lot! Best Regards, Peter.

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#80996

Reflow soldering issue | 4 September, 2018

Hi Peter, I read your concerns regarding IC parts not packaged with desiccants and thought you may find our new Type 2 Humidity Indicator card of interest. Please visit https://www.clariant.com/type-2-humidity-indicator-card

Thanks, Elsa

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#81080

Reflow soldering issue | 20 September, 2018

I agree, your PCB has contamination or something.

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#81086

Reflow soldering issue | 21 September, 2018

Peter,

Based on the images, it looks the HASL is too thin. I have seen this a few times when the pcb supplier uses too aggressive of a process to remove the solder. This can lead to oxidation of the underlying copper. An XRF of a pad that won't take solder should tell you if that is the case. A perfectly flat HASL pad can be a bad thing. It might be good for printing,not so much for soldering.

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#81263

Reflow soldering issue | 18 October, 2018

Thin or non-uniform HASL can be checked with SEM/EDS analysis, e.g. https://www.semlab.com/bad-hasl/

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#81309

Reflow soldering issue | 25 October, 2018

Look at the Stencil man!

Give me a call offline if want, I'm with Stentech, tooling & stencils...

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Metcal soldering rework

used pcb assembly equipment - lel semi