Alejandro.

I have also found the same problem as you are describing and for us it is even
worse as we are working with 5mil of paste. Luckily, our placement machine has
a clever laser scanner vision system that can measure the lead coplanarity and
if the part fails it will be rejected. However, because these parts are within
the manufacturers spec. we cannot send them back and they are usually to
expensive to scrap (especially in the current economic climate) so we have to
use them.

To maintain quality, these rejected parts are marked with a paint pen or
capton dot which will then prompt inspection to double check that particular
part.

Mark Austin
(Process Engineer)
ACW Technology Ltd.
UK

===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at
14/08/02 19:02
>Hello to All,
>
>What is the correct value for coplanarity in a QFP208?
>The specification and one JEDEC standard indicate that the maximum
>coplanarity is 0.08mm.
>I have found that this value may not be appropriate since I have seen that
>this type of value causes Non-solder problems.
>Additionally 0.08 mm represents more than 50% of the height of the solder
>paste deposit (assuming a 6 mil or 0.15mm stencil).
>I measured the coplanarity in the components with Non-Solder problems and it
>varies from 0.04mm to 0.06mm but the vendor
>replies that the components are within spec.
>I measured another part number from the type of component and same vendor
>and I found that the maximum value of coplanarity is 0.04mm and the average
>is lower than 0.02 mm.
>
>Have you ever seen this type of problems?
>Is there another standard about the coplanarity of the components?
>
>Regards
>
>Alejandro Becerra
>
>
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