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Way to solve PCB warpage

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#63244

Way to solve PCB warpage | 7 December, 2010

Dear All I hope I can get some advice of PCB experts in here.My problem is - after wave, our big board, 640x420x1.7mm, had a warpage when the board was cooled down after wave. PCB was flat while being warm.I had tried with many type of pallet and made the space wider to extend the PCB freely but the warpage was still there. look forward your advice.

Thanks

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#63247

Way to solve PCB warpage | 7 December, 2010

Warpage tells you that design and/or fabrication process and/or assembly process need[s] to be corrected. Here's a link to a recent thread on SMTnet that seems to answer some of your questions: http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=62267

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#63325

Way to solve PCB warpage | 17 December, 2010

Hi Dave

Thanks however the Forums you mentioned isn't enough to solve my proble, PCB warpage after cooling down. Hope someone can advise me more.

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#63335

Way to solve PCB warpage | 17 December, 2010

I believe there is a lot pertinent information in the thread that Dave forwarded...

But (IMHO)I think you can look at two things first. First, is your wave solder process friendly to this large PCB, is there enough pre-heat in the board before it hits the wave? If your process is set up, then you can look to the manufacturing of the PCB, is the design of the PCB and the balance of the copper layers friendly to the manufacturing process?

Beyond that, you might be stuck with creative fixturing or perhaps even reduced expectations.

When it comes to warpage, in my experience it often comes down to a less than optimal PCB design (and nothing can ever be perfect) if the process itself is robust.

Again, just my opinioins.

'hege

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rem

#63339

Way to solve PCB warpage | 18 December, 2010

I experienced warpage on a 7'x 13" long board, unfortunately my oven does not have center support. I use stiffeners on both of the short ends. It fixed my problem.

Some of the things I was experiencing with the warpage on the second pass were placement issues due to the crown in the board. Also, for selective solder it was almost impossible to set a Z height consistently across a warped board. I am able to maintain both of these now. The stiffeners I use are made out of bamboo and I cut to length. You can also use fiberglass or metal ones.

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#63342

Way to solve PCB warpage | 19 December, 2010

Hi Rem Woo, ur board is such long one,7'. Our PCB is only 2' long but 3.5kg weight b4 solder. We use wave machine to solder it and PCB was sit on the pallet. all PCB side lengths are pressed by clamps. PCB was flat just after wave, however there was a warpage on the sides when PCB cooled down. Anyway, we use Chasis to flat board b4 sending to customers. Thanks

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rem

#63352

Way to solve PCB warpage | 20 December, 2010

7' is a typo, sorry for that. We have 7"x13". But I will be running some at 18" in a few months.

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#63475

Way to solve PCB warpage | 10 January, 2011

What we use for boards the engineers made to big is aluminum flat bar 1/8 to 1/16 thick about 1 inch wide. we fold it in 1/2 so it fits snuggly on the pcb and just press it on the ends before reflow. id assume the same thing would work on wave but you might get some bonus solder inside it.

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#63478

Way to solve PCB warpage | 10 January, 2011

Hi Eadthem

Your way isn't work for our big size Board(620x440x7mm).After pressing the Alu Bars on the edges, the warpage happened more wider.So, we r using clamps to adjust PCB expension. Anyway, thx for sharing.

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