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Cracked SMT Capacitors

Igmar

#6854

Cracked SMT Capacitors | 13 June, 2001

Have anyone seen this problem:

Capacitors (100nF 0805) placed on PCB and then appear cracked after reflow. After reflow, the solder joints look visualy acceptable. Then capacitors fail during testing. When attempting to remove capacitor with hot soldering iron, end-caps of the capacitor comes loose from capacitor, and capacitor seems cracked. Is this a process or component problem? Any ideas?

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Justin

#6859

Cracked SMT Capacitors | 13 June, 2001

Yes, I've seen it recently and it's most likely a component problem. A cap is essentially a sandwich comprised of multiple layers. the layers are either wet film or dry film. The end terminals may either be hot soldered or sputtered so there are a multitude of possible causes for the failure at the component manufacturing level. Regards, justin...

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DNC

#6862

Cracked SMT Capacitors | 13 June, 2001

Igmar,

Have had similar problems in the past caused by different factors.

The first obvious area to check is in your pick and place machine. Too much force in the Z-Direction may cause micro-cracks, which are not apparent, until the board is processed through heat.

The other areas to check is if the board is panelized check the depanelization process. Any stress being applied to the assembly while depanelizing may also cause micro cracking or loosening of the terminals.

I would follow the process through paying especially close attention to any stress causing processes.

Good Luck.

Deon Nungaray GMI USA

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DNC

#6863

Cracked SMT Capacitors | 13 June, 2001

Igmar,

Have had similar problems in the past caused by different factors.

The first obvious area to check is in your pick and place machine. Too much force in the Z-Direction may cause micro-cracks, which are not apparent, until the board is processed through heat.

The other areas to check is if the board is panelized check the depanelization process. Any stress being applied to the assembly while depanelizing may also cause micro cracking or loosening of the terminals.

I would follow the process through paying especially close attention to any stress causing processes.

Good Luck.

Deon Nungaray GMI USA

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#6870

Cracked SMT Capacitors | 13 June, 2001

Lotsa ways to bust caps. First: placement force; Second: thermal stress; Third: poor pad design. Forth: then, ummm maybe the cap supplier.

Please describe the crack in more detail. Where does the crack start? Where does the crack go?

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CPI

#6914

Cracked SMT Capacitors | 15 June, 2001

I Agree with Dave, Check spec on cap some devices have temp constraints (can exceed x degrees for more than x time or can not exceed a certain ramp rate). Check that then go through the rest of the process chances are its not your machine if no other components are cracking unless the component dimensions were entered incorrectly. is the board populated on both sides? if so are the parts being cracked on the side that was run first if so check support pin setup. Check Depanel method, handling method, etc....

You�ll find it!!

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Scott D

#6916

Cracked SMT Capacitors | 15 June, 2001

Igmar, I would check a couple of things. First, check to make sure your oven profile is acceptable. You do not want to shock the parts. Second I would check to see if the parts are breaking in a consistant pattern. Are they always split at the same end, in the middle, etc.? Next I would check your pick and place machine (maybe you would do this first). Check to make sure the nozzle end is not broken so that the nozzle is actually what is cracking the component. Next I would check the program and make sure you height specs are acceptable. Depending on the machine you are using there are different ways to do this. But I have seen in the past where a z-axiz height is off slightly, which is creating a hair-line fracture in the part, that when heated appears to make it look as if the oven is causing the problem. If you have recently changed vendors for that part there may be a slight difference in body size also. Those are the places I would start to look...I think if you check those things you will find where this is happening. (It also could be a bad lot of parts too!) Anyway, I hope this helps and doesn't confuse you...please drop me a line and let me know how you make out! ScottD9248

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Dean Stadem

#6919

Cracked SMT Capacitors | 18 June, 2001

Igmar, If these parts are epoxied in place, and subsequently wave soldered, I would bet you a cup of coffee that they are cracking due to the thermal shock of the wave. Typically there is a valley or dip in the temperature after the pre-heat in the wave, but prior to the pot. If you are talking about ceramic chip caps, it is nearly 100% probable that the cracking is heat-related, not mechanical. Ceramic chip capacitors are really pretty tough little guys. Mechanical cracking is usually easy to pick up, as it is typically caused by fixtures or handling whereupon the cracked components are all in the same location. An operator performing solder touchup or rework while using a solder iron set at too high a temperature can also cause chip cracking. But if these assemblies are being wave soldered, I would start looking at that process first. If reflowed only, then verify the ramp rate is less than 4 deg. C per second during rampup. The other place I have seen the cracking take place is at test, where a tech is trying to make good electrical contact on a bed-o-nails fixture. I have actually seen them jump up and down while pushing down on the board. Please let me know what the cause turns out to be. Dean

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#7109

Cracked SMT Capacitors | 28 June, 2001

One more place to check, ( if cracked caps are apearing in the same location on all boards), are board supports in your pick and place machine. I've had instances where operators are not tightening board supports down causing them to shift during production. This caused a cap cracking problem. You'll get it!

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