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Crazing or Delam - Thermal or Mechanical?

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#59083

Crazing or Delam - Thermal or Mechanical? | 17 June, 2009

Any thoughts on this will be appreciated, thanks in advance for reviewing.

This assembly has been processed in our facility by going through a press operation (~ 1731 lbs), then into wave solder. Note the discoloration around the pemnut. The discoloration does not appear after the press operation, only after wave soldering (not a verified statement). We have been running this assembly the "same way" for a couple years at production volumes of about 200 per month and have never experienced this prior. 220 out of 250 assemblies on the last production run exhibited this.

Is this a defect by IPC-610 D? (we believe it to be) Is the failure mechanism mechanical or thermal (or both) Is a cross sectional analysis the preferred means to identify acceptibility or is visual inspection enough to reject?

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#59088

Crazing or Delam - Thermal or Mechanical? | 18 June, 2009

Do you know what material type and brand was used.

example: Isola IS410

Regards, Mike

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#59092

Crazing or Delam - Thermal or Mechanical? | 18 June, 2009

We'd call it delamination and ask our board fabrictor to come over and -off replacement baords.

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#59098

Crazing or Delam - Thermal or Mechanical? | 19 June, 2009

Thank you for your responses Davef and Boardhouse.

The material used is Iteq Corporation IT-180.

I performed more testing yesterday and found the following: I could insert Berg Pins into the assembly at various locations or a Pem. None of these activities would "highlight" the masking. Only after wave solder (250F pot temp/105C measured topside PWA preheat) would I get the measling/crazing/delam response and only in this one particular area, however if I ran the assembly through the wave solder again, other regions where Berg pins were insert would also present this non-conforming appearance. I am sending out some processed assemblies to Robisan Labs for microsections today.

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#59131

Crazing or Delam - Thermal or Mechanical? | 25 June, 2009

In the life of this product that you have been doing this process, has the material alway's been IT180 material?

One problem with Lead free material is that it is more fragile that standard FR4 Epoxy laminate. And is known to have chipping or fracture issues due to the ceramic like nature of the material.

Couple things to check: What pre-preg was used? example 7628 1 ply pre-preg or 1 ply?

This could be more than a Board shop issue, Root problem could be product design, material selection, tolerance issue due to over or undersized hole verse tolerance issue on pem, pre-preg material past shelf life, poor temp control in pre-preg inventory room.

Have your board supplier send you the material stack up used for the product, check this against customer Print to make sure correct stack up was used. Have them get Material supplier involved and have them check lot codes of material to make sure it was within its shelf life.

Just a couple thing to look into.

Best Regards, Boardhouse

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