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Pogo Contamination

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#55963

Pogo Contamination | 13 August, 2008

Hi there. We have had troubles with pogo contamination on ICT fixtures causing false failures (Pictures attached). Currently we're spending about 10k on pogo replacement but still having problems. I recomended to clean pogos with a defluxer but Test equipment argue that cleaning causes pogo to bend, do you have a defined routine for cleaning your fixtures?

Currenlty we're running FR-4 HASL boards and Indium NC-SMQ92J solder paste, we put solder on test points (tried w/o solder with not good results).

Any advice will be greatly appreciated.

Manuel.

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#55966

Pogo Contamination | 13 August, 2008

Looks like the flux is winning this one. Here's one from the fine SMTnet Archives: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=4649

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#55969

Pogo Contamination | 13 August, 2008

Hi dave, thanks for your reply I tried to locate "Techni-Tool 872M1034" on the webpage but I found:

https://webvia.techni-tool.com/VIA/viaImagePageIndex.jsp?row=3&pgName=viaListProducts.jsp&searchText=CH8C&modifier=CH8C&reqTitle=TITLE_VIAUSERDOCLIST&newWindow=Y

is simmilar with the brush that you posted?

what I recommended was to purchase a similar brush, instead of the "dental bursh" style. then just down the base of the fixture in order to expose only the tip of the pogo pins, wet the brush wit flux remover and brush the surface of the pines. I recommended to do this every shift or setup.

For the SMT process side, somebody told me that on a DOE performed regarding the same issue, they tried with different solder pastes (I don't remember the manuf), different profiles (RSS Vs RTS) and solder paste amount on the test point. what he told me was that surprisingly neither solder paste nor profile was a significant factor, but the solder paste amount made a significant difference.

Accoring with that person, the higher amount of solder created the surface of the test point like a "cone" instead of a dome shape, thus making the tip of the test point cleaner because the flux bleeded down from the tip by gravity or something. I havent tried but I think it will be interesting to try.

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#55980

Pogo Contamination | 14 August, 2008

Comments are: * Link you posted to your brush actually connects to a general catalog page. * Not sure what solders your friend was using, but pastes leave different residues that affect probing. Some are soft and gooey, others are hard and brittle.

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#55981

Pogo Contamination | 14 August, 2008

> Comments are: * Link you posted to your brush > actually connects to a general catalog page. * > Not sure what solders your friend was using, but > pastes leave different residues that affect > probing. Some are soft and gooey, others are hard > and brittle.

*Part number for brush: 758PR426 *yes, basically what he told me was that both pastes leave a "soft" residue, similar to what we see on our pogos (like a gum residue); basically the intention is to let the upper-test point side "flux-free" (sketch attached).

regards

P.S. drawings aren't eggs, should be test points

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#55996

Pogo Contamination | 15 August, 2008

Hello,

First time user here. What kind of flux are you using?

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#56047

Pogo Contamination | 19 August, 2008

Basically, Brushing the pogo pins with dry anti-static brush will help but, cleaning it using solvents is not that advisable because it only leaves some residue that will further cause contact problems.

Looking at the picture it seems that the UUT's have tremendous flux deposits, how many stroke count were you able to make before you encounter contact problem on your probe? If you have a very low stroke count, I guess you have to consider doing a cleaning process prior to ICT.

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