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How to Differentiate Class 3 and Class 2 products in terms of process

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#73285

How to Differentiate Class 3 and Class 2 products in terms of process | 29 December, 2014

Dear All,

I'm just a budding engineer in EMS field. Here we used to manufacture different classes of PCBA.

I would like to know about different process that need to be considered while manufacturing class 3 product. If we are going for microscopic inspection then, need to know why it is required.

Is there any inspection process which differentiate class 3 with other classes. such as 100% microscopic inspection, 100% dage or 5DX-x-ray inspection etc...

If any one familiar with this , kindly advice

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#73286

How to Differentiate Class 3 and Class 2 products in terms of process | 30 December, 2014

I've always approached it like this: Design your processes and perform your work to class three standards, and inspect to the standard that is acceptable.

That is, all work should be performed to the highest degree of quality. When the work is inspected, though, inspect to the level that is acceptable. There's no sense in spending time and money reworking items that are acceptable to class 2 standards when delivering class 2 work. As an example, take barrel fill on through hole devices. Class 2 allows 75% barrel fill with solder wetted to the lead of the device; class 3 requires 100% barrel fill, with solder wetted to the lead. When delivering class 2, do not spend the time to rework a joint that is acceptable (do spend the time to improve your process, however).

Is microscopic inspection necessary? That depends on your eyesight :) I inspect everything under a scope, because I don't feel that I can adequately examine some solder joints without the magnification.

Cheers, ..rob

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#73296

How to Differentiate Class 3 and Class 2 products in terms of process | 6 January, 2015

How about rework (touch-up) for Class 3? Some say that you are not allowed to rework anything for Class 3. Though I have not found any proof for this 'requirement' in the standards.

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#73297

How to Differentiate Class 3 and Class 2 products in terms of process | 6 January, 2015

I can't say I've ever heard that you shouldn't rework class 3 products.

Since class 3 and class 2 are inherently inspection standards, rework might be required to meet class 3 specs. In the past, that has been an issue, as everyone wants to produce perfect assemblies on the line, when perfection is not, necessarily, what is being paid for. A couple of companies ago, we realized that we were losing some time, and therefore money, on reworking items that met class 2 standards.

cheers, ..rob

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#73313

How to Differentiate Class 3 and Class 2 products in terms of process | 10 January, 2015

#73314

How to Differentiate Class 3 and Class 2 products in terms of process | 10 January, 2015

Rework is acceptable in class 3 but hardware defects shall be documented before rework and rework shall be documented.

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#73317

How to Differentiate Class 3 and Class 2 products in terms of process | 10 January, 2015

> class 3 requires 100% barrel fill

Class 3 requires 75% vertical fill of solder for component with less or more than 14 leads. Not 100% fill.

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#73325

How to Differentiate Class 3 and Class 2 products in terms of process | 12 January, 2015

The closer your inspection the more defects you will find, the more rework you do the possible cost you will add and the potential increase of damage you could do to your products if rework is not up to a machine copyable standard.

"Is there any inspection process which differentiate class 3 with other classes. such as 100% microscopic inspection, 100% dage" This (and someone quote me if I'm wrong) kind of inspection is not governed by class in IPC-610 but by land width and land diameter groups.

X-ray is more associated to void inspection.(which is governed by class(and different component types))

you cannot really easily outline what differences you need between class 2 and class 3 and there could be many or only a few. It depends on the product you make.

Class is outlined by the customer or your R&D team.

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