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Stress induced during V-score depaneling

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#64473

Stress induced during V-score depaneling | 13 June, 2011

Hello, does anyone have any information on stress induced during V-score depaneling. We are using a machine with a fixed blade on the bottom and a free rotating blade on top driven by a motor. We have had some cracked capacitors on the edge of an assembly and one thought is the depanel process.

Thanks

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#64475

Stress induced during V-score depaneling | 13 June, 2011

Cracked parts close to the edge on pizza cutters are a common problem. There are a lot of stresses on the board as the blade cuts through the board. Raising the blade height so that the boards are not cut clean through will help. You will have to finish separating by hand but it can reduce or eliminate the cracked parts. Also make sure the blade is sharp and try slowing down the motor speed. You can also get the board manufacture to slightly increase the depth of the score but that’s a last resort. It could cause the boards to break apart during processing. High reliability electronics need to be routed to prevent cracked parts. You need to monitor this closely because the parts can fail in the field even after testing.

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Ken

#64478

Stress induced during V-score depaneling | 14 June, 2011

what is the clearance between the chips and the edges?

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#64479

Stress induced during V-score depaneling | 14 June, 2011

.088" from the edge, running parallel to the V-score, 1812 package size. Kemet part number C1812C105K5RACTM.

Thanks

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#64480

Stress induced during V-score depaneling | 14 June, 2011

Thats .088" from component edge to pcb edge.

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#64481

Stress induced during V-score depaneling | 14 June, 2011

I use a pizza cutter with parts closer than that, but they are small-ish (<=0805). Could the problem be related to the larger size of the part?

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#64483

Stress induced during V-score depaneling | 14 June, 2011

Travis H: Are both pads of the component the same distance [0.088"] from the edge of the board?

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#64484

Stress induced during V-score depaneling | 14 June, 2011

We had a problem with 1825's close to the edge which were being sheared when the breakaways were flexed and removed manually, the resolution was to get a de-panelizer which eliminated the problem we were having.

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#64497

Stress induced during V-score depaneling | 15 June, 2011

Yes, both pads are the same distance from the edge. I also included a picture of a cracked part.

Thanks,

Attachments:

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#64498

Stress induced during V-score depaneling | 15 June, 2011

This might sound stupid but... We had a similar issue and the solution was depaneling the panel upside down. Take this advice at your own risk...

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#64500

Stress induced during V-score depaneling | 15 June, 2011

Classic mechanical stress crack pattern. Pretty

Try baking your boards for 2 hours at 100*C

Minimum spacing between board features and v-score or break away is 30thou.

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Ken

#64503

Stress induced during V-score depaneling | 16 June, 2011

thats very close to the edge. it is preferable to have at least 3mm clearance to edge, or more ideally 5mm. If the chips are too near to the edges, you might want to modify the panel by routing through the area next to the chips. This would eliminate stress when depanel blades approaching the area.

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#64510

Stress induced during V-score depaneling | 17 June, 2011

One problem you may have with deeper scoring is not so much broads breaking apart unintentionally, but warping upstream while on the SMT line which can cause sagging. This may give you transport issues from one machine to another, and if you have an AOI, can cause alignment issues with your templates (We use board supports on the AOI to alleviate this issue, but it is caused by thinner 30mil pcbs.). The size of the part is not the issue. We have had similar issues in the past with 0603 chip caps; although, in our case, the parts were always vertical to the edge of the board, not parallel.

Tombstonesmt had a suggestion of turning the board upside down. That's not a silly suggestion, it can make a difference depending on how your board is flexing. We had an issue with an 0603 part breaking, all of a sudden. Nothing, we thought, had changed in the process, until we witnessed one of the operators cutting the boards at a different orientation, and on a different line, then had been done in the past. She was cutting component-side up. Traditionally we cut these particular boards upside down. Call it luck, but they were normally cut on different depanelers that did not allow, due to clearance, the boards to be cut component-side up; therefore, they were forced to cut them upside down and we never had issues, until this new operator began cutting the boards on another line and at a different orientation. It wasn't the depaneler itself. We tested it with the board upside down, and the issue stopped.

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