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Cracked Tantalum Capacitors

Wayne Smith

#27540

Cracked Tantalum Capacitors | 8 March, 2004

Currently experiencing a problem where the plastic molded bodies of tantalum capacitors are cracking during my SMT processing.

Caught after our conformal coating process. I don't know where in the process they cracked. Currently running an experiment to pinpoint the exact point in the process this is happening.

Anyone out there seen cracked tantalum caps? (The molded bodies, not the solder joint)

Any feel for what my root cause could be?

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Gabriele

#27542

Cracked Tantalum Capacitors | 8 March, 2004

Have you considered those Tant Caps could be moisture Sensitive Components ?

During last year, several Brand Suplliers classified their Tant Caps as Moisture Sensitive Level 2a (4 wks out of dry pack before reflow, see J-STD-033a) some even MSL:3 (168h). It seams major reasons are due to Popcorn effects or Outgassing. Same Part Number of Tant Caps,a couple of year ago' use to be classified not Moisture Sensitive (MSL:1).

Regards GLS

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#27544

Cracked Tantalum Capacitors | 8 March, 2004

What type of P&P machine? Useing any Placement force? Ramp speed in reflow? PCB thickness properly defined? Tooling supports too high? Any doubble stacking of parts? Occuring with only one part manufacturer? Start with processes where problem is noted and work backwards to when damage disappears. This is assuming parts are ok when recieved.

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Ken

#27553

Cracked Tantalum Capacitors | 8 March, 2004

I vote furnace is causing popcorn affect. Seen this many times over the last 4 years....especially if your buyers are buying parts on the "grey" market.

Unless your running mechanical cenering machines (GOD I miss the Dynapert days)it's probably steam epansion causing your problem.

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#27555

Cracked Tantalum Capacitors | 8 March, 2004

Wayne: Please describe the location and angle and direction of the crack relative to the board.

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John Soileau

#27556

Cracked Tantalum Capacitors | 8 March, 2004

I expierenced this while at I-PAC Manuf. when the reflow profile was too hot in the perheat & soak zones.

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Reflow Oven

HeatShield Gel- thermal PCB shield during reflow