Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wavesoldering Defect

Adam

#30489

Wavesoldering Defect | 14 September, 2004

Hi

Has anyone see a defect,where after one pass over the wave, pins on conectors seem to have a tenancy to have a mimimum solder fillet on the bottom-side of the board. There seems to be no trend, It could range from half a dozen to two dozen from board to board. I have optimised the profile over and over again, tryed diffferent wave height settings, but still no success. The only I can get satisfactoy results, Is to give the PCB two passes over the wave. What is this phenomenon ? Why can't I achieve satisfactory results after one pass ?

We are using an RMA based flux.

Thanks in advance.

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HOSS

#30516

Wavesoldering Defect | 14 September, 2004

Adam,

Is your fluxer giving you good coverage into the holes and to the top of the board? If your hole size in relation to the lead diameter is too small, this may be contributing. I'd check your fluxing first though.

Just an aside.....We just switched from a Kester RMA to AIM's 715 water soluble flux in our process and the difference is like night and day. If you aren't required to use RMA by your customer(s), I'd seriously consider changing.

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MikeF

#30519

Wavesoldering Defect | 14 September, 2004

I would need a little more information to be able to rule out some of the possible causes. Have you checked to see if the pins with the minimal solder have anything in common, do all have traces to them? or internal power or ground plane connections?

You may have a component problem, is it the same connector on different board designs?

Check your flux application, is it even across the board? Try a board with no parts and run it through with only the fluxer turned on, and the preheater and wave solder off. Check the flux residue around the connector compared to the rest of the board.

Finally, do the solder joints you are getting meet your workmanship requirements? What are the top side fillets like, on both the good and bad bottom side fillets?

This info will help us give you better info on the possible cause or causes for your problem.

MikeF

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Adam

#30522

Wavesoldering Defect | 15 September, 2004

I have chceked the fluxing application, I seem to be getting good consistent coverage across the board using our foam fluxing system. Good flux penetration on the top-side of the through-hole plating, as this was checked using a fax paper.There is no trend, with regards the type of connector or a region of the board.

Unfortunately we are not in a position to change our flux. The RMA based flux is a specific customer requirement. It is Alpha 615-25. Although we are getting excellent top-side fillets, the solder-side fillets are at a minimum, are failing at inspection.

Thanks for the info so far.

Adam

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#30527

Wavesoldering Defect | 15 September, 2004

It may be worth baking the boards for an hour at 120C and then trying it straight away do not leave them lying around.Is the fillet shallow and inverted back into the board. Do you have any blow holes as well? Cheers Greg BLT

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Adam

#30554

Wavesoldering Defect | 16 September, 2004

No blow-holes, only minimum solder fillets.

Adam

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Rob

#30555

Wavesoldering Defect | 16 September, 2004

Hi Adam,

What machine are you running?

Rob.

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Adam

#30571

Wavesoldering Defect | 17 September, 2004

Rob

The machine is SEHO MWS8240, Fitted with a foam fluxer, a combination of IR,Quartz and Convection preheaters together with a chip and delta wave.

Adam

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#30576

Wavesoldering Defect | 17 September, 2004

Adam,

If you use the chipwave on that board, eliminate the chipwave on one board and see if this eliminates the problem with the insufficient solder on the connector.

Regards, Patrick

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Adam

#30601

Wavesoldering Defect | 20 September, 2004

Patrick

Tried That, unfortunately it didn't work.

Adam

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Rob

#30604

Wavesoldering Defect | 20 September, 2004

Hi Adam,

We had a reverse of the previous - if we didn't have our smartwave running at at least 750 RPM behind the main wave, the pressure dropped & gave us inconsistant soldering.

Otherwise...

1) are the components tarnished at all, or stored in conditions they shouldn't?

2) Any residue left on the board from the supplier? - try washing

3) Inherent problems on the action of the foam fluxer? - try hand spraying a board and see what happens.

Hope that helps,

Rob.

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#30655

Wavesoldering Defect | 22 September, 2004

Just a thought, Solder flows to leads of parts and will tend to flow to hotest point. Im not shure but top side temprature might be hotter than bottom side. wouldent this cause solder to pull further up lead after leaving wave.

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#30718

Wavesoldering Defect | 27 September, 2004

First, Your flux is no good replace it. second, Check for pre- oxides. The smaller the component or the leads makes it difficult to solder specially if it has oxide. Thrid, check the board to wave parallelism. Maybe your wave is not parallel to the board that is why you have to repeat the solder process all the time. A good tool I always use in finding the parallelism of solder wave to board is the solder wave optimizer made in Israel. get one you'll be amaze!

Arman

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Vee Sar

#30754

Wavesoldering Defect | 28 September, 2004

Adam,

I would first check hole to lead sizes on the components that you are having hole fill issues with to see that the spacing is withing spec. Second, check for oxides on lead tips, and contaminated leads that cause poor wetting and insufficient solder fillets. Last I would check flux spread/coverage and wave parrelism. Best way to do this is to use a glass plate. The one I recommend is the lev check plate, you can read more about it at this link - http://www.nec.itgo.com/part07.htm This will allow for you to minmic the exact process, flux spread/coverage, chip wave coverage area, parrelism, and delta wave coverage area, parrelism. Adjust all those parameters until you get what you want and that should solve your problem.

Regards, VS

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