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Problem with solder joints in wave solder

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#71567

Problem with solder joints in wave solder | 9 January, 2014

Hello!

I have a problem with one of the products here, we use a pallet to run the board on the solder wave, when the board gets solder and you inspect the board you notice that for some reason the first pcbs that touches the wave are ok, even a little bit more solder that you need, but if you check the last pcbs they all look almost flat like when you put a low rpm on the lambda wave and barely fills the thru hole.

We dont come to an agreement one part thinks the problem is with the profile the other have thinks the problem is the solder pallet

What do you all think?

need help!

thanks

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#71574

Problem with solder joints in wave solder | 10 January, 2014

One thing you could check/monitor is the temperature in the pot/wave. As boards run across the wave, they will cause fluctuations in the wave temperature. The heaters should hep with minimizing this; but, if you're running a lot of boards in quick succession, it's possible that by the time the last board gets there, the wave is no longer at a good temperature for the profile.

Another consideration could be the wave pallet. If you're using a minimal quantity of pallets while running, it's possible that boards late in the run are being run on pallets that are too hot, affecting the solder quality.

Cheers, ..rob

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Vince W

#71582

Problem with solder joints in wave solder | 13 January, 2014

A little confusion here. Are you running several boards in one pallet and the last boards are looking poor or is the issue getting worse as the day progresses (like as the pallets get warm)? - If it is the last boards in the pallet, then you may want to look at the board warping and raising. - You could also look at pallet and see if there is proper reliefs for solder flow. - If you can turn the pallet around and run it, see if the issue stays with the pallet orientation or still last through. This may indicate something. - If it is just as the day progresses.. I would be looking at what Rob suggested. good luck.

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#71590

Problem with solder joints in wave solder | 15 January, 2014

we do that and there's a variation on the solder temp. sometimes around 10 degrees, we have 2 solder pallets that are run in intervals of roughly 3 1/2 minutes a part (the time that take the operator to put all 3 terminals in a 42 pcbs per board, and the problem is constant, by that I meant in every board there's a 1 - 4 pcbs with the problem some are too much solder and others the solder do not form a visible fillet with the terminale blade or it just a hole or is flat without the fillet the only thing to do is amp the rpms causing solder excess or lowering the solder pot causing insufficient solder.

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#71620

Problem with solder joints in wave solder | 21 January, 2014

Armando,

Is the problem in the same spot on the board with every run?

If so, there might be something about that particular location that is part of the cause (ie. ground or power plane connection).

It sounds like you're seeing blow holes, or insufficient fillet on the top side of the board. If this is true: 1. Verify against IPC that the assemblies fail to meet spec...nothing like chasing a process problem down when you don't need to! 2. Verify the consistent application of flux through the machine. 3. Try applying some flux to the top side of the board, as well as whatever flux you're applying to the bottom side.

Blow holes are caused by releasing gas. Ensure that there is room for the solder to outgas around the componet (sometimes, components mounted too tightly to the board can prevent efficient outgassing, causing blow holes).

The insuficient flow/fillet could be caused by: 1. Contaminated components (flux should correct this) 2. Insufficient dwell time (though I'd expect to see that throughout the board). 3. Insufficient heating (which could be caused by wave temperature variation, or a difference in thermal characteristics at that part of the circuit (ie. large copper pour/ground plane, no thermal relief vias, etc).

Cheers, ..rob

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