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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


bending PCB Panel

sergiovito

#24854

bending PCB Panel | 17 June, 2003

Hello Everyone,

I am assemblying a special Panel PCB, dimensions 330 x 250 mm with 8 single PCBs in it. After SMD reflow oven, the panel is bending and this is impacting in the next process - solder machine. some areas on the PCB aren't touched by the solder properly, and the final quality is very poor!!

Can someone help me to solve this problem???!! Thank you!

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#24856

bending PCB Panel | 17 June, 2003

We had a product a couple of years ago that did the very same thing, we increased the amount of webbing to reduce the amount of warping.

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#24857

bending PCB Panel | 17 June, 2003

How are the 8 units distributed on the panel? 1 X 8, 2 X 4? Are there "V" groves scored in the panels to "break away" the units? Do you run on edge conveyor in the reflow oven?

You need center support if you have 2X4 pattern with "V" grooves.

Or use a stiffener bar on the edges of the card where the bend is.

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JB

#24859

bending PCB Panel | 17 June, 2003

After you depanelize your product, use the remaning "frame". Just set your panels on the "frame" before reflow. That will give some extra support.

JB

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RDR

#24862

bending PCB Panel | 17 June, 2003

Is this a single sided or double sided board?

We run the first side flat on the oven belt this keeps the board flat for the second side assembly.

If the board warps during the second reflow process we will make a support fixture to carry the PCBA on the belt again instead of on the edge hold chain. This can sometimes be as simple as a couple of FR4 sticks placed underneath the assembly with the components resting directlt on top of the sticks. You need to make sure that no parts come into contact with the oven belt or they can become dislodged/moved.

If either of these can't be done a carrier fixture will need to be designed to provide support during reflow. We usually use a "picture frame" type base with standoffs located at key points to support the board (tooling holes work great if they are in the right spots otherwise any empty area on the board works)

If you only want to flatten for wave process I would reccommend the use of dedicated fixtures OR you can buy universal frames from companies like FANCORT These frames have a multitude of accesories such as solder dams, "sky hooks", etc... They also manufacture board stiffeners that are made out of titanium that will straighten and hold a board flat during thermal processes.

Hope this helps

Russ

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