Chip Component Cracking During Pick/Place

Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting. Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes

Phil Zarrow With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes. Jim Hall A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

Transcript

Phil
Welcome to The Board Talk. This is Jim Hall and Phil Zarrow, the assembly brothers, who by day go as consultants with ITM Consulting, but here on Board Talk to help with your assembly-process questions.

Today's question comes from D.C. He says, "Occasionally we notice chip resistor cracking during placement. Most often the cracks are in the center of 0201 and 0402 size chips.

Wow! How the heck do you see them? "Does your experience indicate this is typically a placement equipment adjustment problem, excessive force, or could it be a component design issue?"

Well, let me start off by saying there has been occasions in the past, not frequent, where components do come in cracked, so that even nominal placement or any handling can crack them. They might have been co-fired incorrectly, but how would you inspect them? You could have some poor sap in incoming looking at the reels, especially 0402s and 0201s, looking for cracks, well, hey, everybody's gotta do something.

Jim
Though you would probably see cracks of this type universally across the reel of components. So you could look at the history of the failures and determine if it's a materials problem.

Phil
We're assuming that you have inspected these components after placement, prior to reflow, and prior to singulation, so eliminating other causes of cracking, in that they are indeed, from what you see, a mechanical crack.

Jim
The first thing I would recommend with chip handling in any placement machine is to look at the nozzles. Make sure you have the right nozzles, that they're not worn, and so forth.

Worn nozzles have been a source of many problems over the history of chip placement. Haven't necessarily heard it associated with cracking, but it's a good place to check it.

Learn how your specific placement machine handles z-axis control. Does it place strictly on pressure? Does it place on absolute z-axis position relative to a zero point? How does it establish that zero point?

Whatever your machine does, make sure you understand it, and that you're programming the machine correctly. Assuming you're doing that, then I would look at the board.

Board warpage is a common problem. In this case you would expect that it would be a bowing up such that the chip in question, where the crack occurred, was actually located on the machine in the z-axis direction slightly higher.

That would be a particular problem if your machine was placing on z-position rather than pressure. A machine that places on pure pressure should be more tolerant of warpage in the board

Warpage, in the board in any of your operations, is a potential problem, so you should try to minimize it. Always use proper underneath board support in any of your machines, whether you're printing, placing, inspecting, doing ICT, dispensing - always use proper board support.

Anything you can do to minimize bowing in general would be a very valuable thing that might help you in this situation.

As you come down in the z-axis, rather than placing the component approximately halfway or one third or two thirds of the way into the solder paste deposit, you're gonna be bottoming out and, no doubt, splattering solder paste.

We're talking about very, very small components so it can be very challenging.

Beyond that, this is Phil Zarrow and Jim Hall.

Jim
Whatever you do, don't solder like my brother.

Phil
And don't solder like my brother.

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