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PTH Ring missing

Views: 1592

Fhail

#40369

PTH Ring missing | 13 March, 2006

Hi All,

I'm new in PCBA process. Recently in my leadfree production we encountered a missing ring on some of the ring on the board after we ran hem through Wave soldering machine. The board has gone through double reflow prior to the Wave soldering. Solder pot temperature is 260 and the contact time is 5 seconds. Solder composition is SAC305 and PCB finished is OSP. I learned that copper dissolution is normal for the solder pot that have more than 50% Tin, but I'm sure the dissolution rate should not be that fast i.e. 4 - 5 seconds.

Pls advise if there is anything else I should look at to trouble-shoot this problem. What is the possibility of having this problem originated at the PCB fab house?

Hope to hear from all the expert ut there.

Thanks, Fhail

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RDR

#40378

PTH Ring missing | 13 March, 2006

First, are you positive that the rings were present before wave?

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Fhail

#40393

PTH Ring missing | 13 March, 2006

Well,I must be stupid if I don't validate this point.Very funny, Russ.

Thanks anyway.

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#40406

PTH Ring missing | 14 March, 2006

If the OSP boards have gone through double reflow I assume that you use an aggressive (halide) flux for wave soldering. SAC 305 is known (search the archives) to dissolve copper faster than other lead-free alloys. This together with an aggressive flux can result in total Cu pad dissolution depending on pad size and copper thickness. I would look first at activity level and nature of the flux and if that doesn't work you need to look into a different board plating like ENIG or immersion silver or any nickel based plating.

You asked, "What is the possibility of having this problem originated at the PCB fab house?" and Russ gave you an answer I don't see anything funny.

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RDR

#40412

PTH Ring missing | 14 March, 2006

Wasn't trying to be funny. 90% of the time when I hear the wave is doing ???????? "we are sure that it is not like that before" I check and the parts are tilted or whatever before the wave.

I had some more suggestions and ideas but..........

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Fhail

#40417

PTH Ring missing | 14 March, 2006

Thanks for all the reply Guys. Your input is very much appreciated.

Fhail

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