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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Re: SMT Chip terminal lifted

PC

#7823

SMT Chip terminal lifted | 17 January, 2000

Can anyone there please tell me what can cause the SMt chip terminal lifted? This happen quite often and I can't find the rootcause for this problem. Does it cause by material/Placement??

Thanks

reply »

#7824

Re: SMT Chip terminal lifted | 17 January, 2000

PC: I guess you talk about something called tombstoning. About causes and adequate countermeasures you will find enough material when you browse the archive with this search item. Try also "tombstone".

Good luck

Wolfgang

reply »

erico

#7825

Re: SMT Chip terminal lifted | 19 January, 2000

Hi wolfgang, I think Pc is not talking about the tombstone cause this terminal lifted is different from tombstone. The terminal of chip is still there but can not be solder anymore so we have to replace the chip. I also facing this problem. So can you all give us suggestion/advice/solution for this and also what is the rootcause?

Thx

reply »

#7826

Re: SMT Chip terminal lifted | 19 January, 2000

Hi Erico, I think it�s just a naming problem. Under the topic of tombstone there are a lot of causes for different appearances of this symptom. Shouldn�t be always the errected position that occurs. In your case it seems that either the components solderability isn�t satisfying before mounting (contamination for example) or within your soldering process something is going awfully wrong so that the solderable surface is dissolved into the solder leaving only unsolderable surface behind. Are there only specific parts involved, is there the possibility of contamination in your assembly workflow, what�s the common factor between those parts, how long is your time over liquidous ? Maybe that doesn�t hit the goal but for I had not been in that unlucky situation you�re in I can only give advice by estimation.

M2C

Wolfgang

reply »

#7827

Re: SMT Chip terminal lifted | 19 January, 2000

PC and Erico: Are yinns talking:

1 A component that will not lie flat on the board? 2 A component that will lie flat to the board that you can't get to solder to the pad? 3 A pad that is no longer attached to the board? 4 Something else. Whazit?

Dave F

reply »

erico

#7828

Re: SMT Chip terminal lifted | 20 January, 2000

Hi wolfgang,Dave & PC:

What I facing are: 1. The component lie flat on the board but only one side can get solder.The pad is ok, problem is with the chip. 2.I desolder the chip and go to view it under microscope and found that there is a line near the chip terminal. 3. What I suspect is this problem can happen at touch up only, what do you guy think?

Thanks to wolfgang and dave.

Best regards

reply »

#7829

Re: SMT Chip terminal lifted | 20 January, 2000

Erico:I can�t even imagine what this line looks like and what it has to do with the soldering problems without having a look at it. Also the restriction to touchup only is somewhat irritating to me. The only thing that I can think of is that in your soldering process material of the termination is dissolved into the solder from the surface where contact is made to the solder. Parts of the termination which doesn�t get in contact with the solder stay as they are. This causes at a close look two different areas at the termination, one with the original coating and one with removed coating and the line you see is the boarder between those areas.This IMO would indicate that the cause is more in your standard reflow process.

This is just my guess based on your discription and might not be the correct answer to your problem.

Maybe some others have different ideas or encountered the same problem already.

Good luck

Wolfgang

reply »

Brian W.

#7830

Re: SMT Chip terminal lifted | 20 January, 2000

It sounds like what you are seeing is leaching of the end cap. You need to check the manufacturer's spec. Many components have terminal barriers, which get a solder plating. Sometimes this plating process is not done well, and the solder plating leaches away from the terminal barrier during the solder process. It can happen in reflow, wave, or hand sodler. What's left might be solderable, if you use a blowtorch. I would suggest you do a solderability test on a sample of the parts off the reel. If you get the same condition, it is a manufacturer's defect.

Brian W.

reply »

erico

#7831

Re: SMT Chip terminal lifted | 26 January, 2000

Hi guys,

Thanks for help. It really help.

reply »

Training Services

SMT Replacement Nozzles