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PCB bows after wave soldering

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Sid

#62082

PCB bows after wave soldering | 18 June, 2010

Good afternoon all,

I have been trying to find a solution to a defect I just noticed. After stencil printing and smt part placement on the secondary side of my boards, I run them through a wave soldering system.

All my components got soldered perfectly but I noticed that my boards now bowed. I could not think of the right solution to this problem because all the boards were handled with utmost care and were prevented from any kind of physical bending or stress. Also, the boards were all flat before I waved them.

I could think of 2 things: 1) Imperfect design of the boards causing solder joints of components to add stress on the PCB, 2) Difference in the coefficients of thermal expansion of the PCB laminate and the stiffner/stand-off placed above the board.

Have any of you guys faced such an issue?

I would appreciate it if you could explain the phenomenon or how you managed to address this issue.

Thanks, Sid.

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#62111

PCB bows after wave soldering | 24 June, 2010

Our best suggestion - get the copper balanced and if possible go to higher Tg materials.

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SC

#62121

PCB bows after wave soldering | 25 June, 2010

Consider using wavesolder pallets that keep the board flat during wave. Keep the board in the pallet after wave until it cools down a bit then remove it.

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Sid

#62123

PCB bows after wave soldering | 25 June, 2010

Thanks for you suggestions, guys.

davef, I am gonna get with my PCB suppliers and talk to them about copper balancing and checking the Tg of the materials they use.

SC, I am working towards designing wave pallets for my boards and try your suggestion.

Once again, thanks guys.

-Sid.

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#62126

PCB bows after wave soldering | 25 June, 2010

i think you need to use a PCB central support. do you know that part ? it specializes in preventing PCB board from bowing during wave soldering.

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#62136

PCB bows after wave soldering | 29 June, 2010

Is this a single PCB or a multi-up array? At the very least you should probably pick up a universal wave pallet, check out AGI or DMI.

-Phil

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#62138

PCB bows after wave soldering | 29 June, 2010

There are some good suggestions here...reflow pallets, and copper balancing.

We would also suggest verifying that your problem is not caused by moisture. How much time passed between first side and second side reflow, and how humid is the environment? Moisture absorbtion into the PCB could also cause warping.

cheers ..rob

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#62163

PCB bows after wave soldering | 1 July, 2010

Sid,

Try baking the boards before running, to insure no moisture. Baking out the moisture will help prevent warping.

Should you need further assistance, we supply fixtures to force the board to stay flat to reduce to thermo shock during wave soldering.

Monica

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Sid

#62166

PCB bows after wave soldering | 1 July, 2010

Thanks to all for their inputs.

@Hexielectronics, I am now trying to assemble the board by attaching it to a frame and removing the frame while waving it. I plan to put the boards back on the frame after the board cools down. Could you explain more on the central support that you indicated in your reply?

@Phil Skiba, this is a single PCB.

@robgd3, My boards are regularly baked after an interval of 4 days and the environment they are assembled in is humidity controlled. I hope that moisture is not a factor that's causing them to bend.

@Monica, I do bake them to take the moisture out. I am investigating the issue further.

Once again, thanks guys!

-Sid.

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#62180

PCB bows after wave soldering | 6 July, 2010

Hello Sid: i don't know where you bought the machine. the central support system is an addition part, it is specially designed to prevent the PCB board from bowing. i know that the wave soldering machine which made before did not include this useful system. but now it is used commonly. you may consult your supplier about the new addition. they may explain you very well about this problem. because i am a manufacturer of wave soldering machine, if our customers require, we will add that part to the machine . hope you will find solution . if you still can not solve this problem, contact me, our engineers know how ,and i shall try to help you. my skype ID is :phoebe_jin

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#62209

PCB bows after wave soldering | 9 July, 2010

Try titanium edge stiffners on the PCB before making solder pallets.

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reflow oven profiler