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SM4007A Genpurpose Diode

Views: 1946

G. eisner

#42058

SM4007A Genpurpose Diode | 9 June, 2006

We are finding this diode not reflowing well. We are having tombstoning issues with this part and only this part on different pcbs. The main thing we find is that under a scope there is blow outs as in air bubbles that look like they have exploded. I am thinking there is contamination on the Components. We had just profiled our oven for the board we were using. My main reason for this thought is that on one of the pcbs we ran thru the processes we had a perfect print on new paste, excellent placement and pre reflow inspection showed all the parts in the correct spots, and then once thru reflow 13 of 200 units had partially tombstoned Diodes. That brings me to component contamination. I realize that this particular Diode is one of the most common used in SMT. Any help or insight would be appreciated.

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Chunks

#42060

SM4007A Genpurpose Diode | 9 June, 2006

I believe this is a MELF, correct? If so, it could be your pad design. Most use a "horse shoe" style that seems to work well. Another thing to look at is your cooling zones. I've seen these parts remain liquidous into the cooling zone where they tombstoned as well. Of course, just as you have said, I too have seen bad plating on the ends of the part too.

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G. Eisner

#42062

SM4007A Genpurpose Diode | 9 June, 2006

No it is a SMA package not Melf. thanks

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RDR

#42068

SM4007A Genpurpose Diode | 9 June, 2006

Pads may be too far apart from each other

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#42081

SM4007A Genpurpose Diode | 10 June, 2006

Chuckie: SM4007A Diode case is D0-214AC

G. Eisner: On tombstoning: * Check reflow profile * Pads per IPC-SM-782 * Reduce amount of solder paste * Check component solderability * Place component accurately * Search the fine SMTnet Archives for background discussions

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G Eisner

#42084

SM4007A Genpurpose Diode | 10 June, 2006

i have pictures available now so if you want send me an email at geisner@pacificinsight.com

Thanks

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