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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Measling

Dave Celestian

#13800

Measling | 15 October, 1998

I have a problem with measling on our PCB's. We saw it on our FR4 PCB's at final assembly yesterday. Is this a defect from the board vendor or something we did in our assembly process when building the PCA's (thru hole). Could the wave solder machine cause this? Most of the measling is in the same location around the leads of a through hole IC (most not all).

Thanks for any help on this.

Dave

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Earl Moon

#13801

Re: Measling | 15 October, 1998

| I have a problem with measling on our PCB's. We saw it on our FR4 PCB's at final assembly yesterday. Is this a defect from the board vendor or something we did in our assembly process when building the PCA's (thru hole). Could the wave solder machine cause this? Most of the measling is in the same location around the leads of a through hole IC (most not all). | | Thanks for any help on this. | | Dave | Meazling is a thermally induced anomaly as opposed to crazing which is mechanically induced. Your wave solder process, if not properly controlled, could be the cause. There may be contributing factors.

If your PCB supplier is not using "good" laminate, prepreg, and core material, this could contribute to the final cause as overheating. Uncontrolled lamination or press cycles can be a factor once again in concert with your possible deficiencies.

It would take some looking into to provide exact cause. Of course, you must be sure it is meazling. It could be crazing or scuffing as the copper moves across the PCB surface exposing glass fabric close to the surface. It also could be dycianimide that has not been properly processed in the resin system.

In any case, be sure it (whatever it is) does not exceed IPC requirements. For further assistance, contact me directly.

Enjoy,

Earl Moon

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