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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


wave solder

Jason

#3845

wave solder | 12 June, 2000

I am new to wave soldering. Any information is greatly welcomed. Here is the problem. After soldering the boards they have a film on the bottom of them and sometimes a white powder looking substance. I have tried decreasing the amount of flux on the board but then i don't get good topside wetting. my board temp coming out of my last preheater is about 225F. my solder temp is at 500F. i am running the wave as high as i can with the lead clearence as low as i can. do i need more heat in the preheaters? If i need less flux how would you recomend making the change. With nozzle speed, turning the flux pump down, less strokes. As i am very new to this any information will be greatly welcomed. Tell me the basics anything at all. I am learing this as i go. thanks for the help :-)

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Jason

#3846

Re: wave solder | 12 June, 2000

after reading some other problems i can tell you that we have an electrovert wave and are using alcohol base flux with convection preheaters. also we are spraying it on...not foaming. we are using an omega wave also. thanks again...if you need more info i will do my best to get it....

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MikeF

#3847

Re: wave solder | 12 June, 2000

Jason, First, check with the manufacturer of the flux you are using. They can tell you what board topside temperature range the flux is designed for. Some other info is needed for the residue part. Is it showing up on the same board, or different boards? Does it seem to be random, or on some percentage of boards, regardless of type or configuration?

A residue all over the bottom of the board would most likely be from the flux, check with the flux manufacturer's tech support people. If the residue is a gray powder in or around the solder joints, I would first look at the dross in the solder pot. If it's allowed to build up too much, it will start getting sucked into the pump and will end up in your solder joints.

Be carefull how high you pump your wave. The higher it is the more turbulence you get, which generates more dross, which means more maintenance on the pot to remove it, and more solder needed to keep the pot filled.

Good luck, Mike F

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#3848

Re: wave solder | 12 June, 2000

Jason: Wave soldering is the coolest thing!!!!

First, so, what�s the chemical analysis of this white res? Can you point us to either tin, rosin, or something else?

Second, how do you know that you are making these white residues? Could your board supplier be giving you a gift?

Third, the fastest way I know to get wave solder connections "white" is to get water on a no-clean flux. In this, my favorite is water washing boards with no-clean flux residues on them. But you can also do it by doing a lousy job of preheating a flux with a water carrier. I know there�s a thread in the archives on this, but I can�t recall the details.

Forth, following close on the heels of #3 above, in some geographic areas, people complain about this every year at this time when the moisture in the air flashes over from not so humid to beaucoup humid.

Fifth, about your set-up: � What�s this "about 225�F"? Is that the preheater set-point temperature or the board temperature at the preheater? � What�s this ____ flux that you�re using? � What�s this ____ conveyor speed you�re running? � How does your set-up process conform to the Chris Shea / Bob Willis methods referenced in the archives?

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Jason

#3849

Re: wave solder | 13 June, 2000

ok now i have some more answers to questions.

the 225F is the temperature as the pcb comes out of the last preheater before crossing the wave.

the conveyor speed is anywhere from 3.65-4.00 should it be the same for all boards??

I am using superflo solids 26F Flux Isopropyl Alcohol (67-63-0). the numbers came straight from the container. i'm not sure what it refers to although i would assume that it means ratio of flux to alcohol.

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Travis Slaughter

#3850

Re: wave solder | 13 June, 2000

Superflo 26F is a no-clean flux, I bet your trying to wash it in water. You could not clean the board that flux will not hurt it at all, that is unless your conformal coating it. You could also run a simi-aqueous wash or maybe a saponifier in your water. No-clean people does saponifier do a good job on that stuff? My favorite choice would be to go to a water-soluble flux, just make sure you get them board squeaky clean if you go this way.

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Chris May

#3851

Re: wave solder | 13 June, 2000

Jason,

If 225C is the topside temp of your board just prior to hitting the wave, I would say this is too high.

Your flux suppliers data sheet should tell you an ideal topside temp for good flux activation, probably around 190C.

According to the Bible(Klein Wassink), white residues can be caused by the solder resist not being cured properly or the flux residues drying out during the soldering process (250C ?).

These white residues tend to be cosmetic only and can generally be dry brushed off.

Soldering In Electronics by R.J. Klein Wassink has everything you would ever wish to know about the soldering process. I suggest that you avail yourself of a copy, but it is not light bedtime reading.

Regards,

Chris.

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