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| Date: | Wed, 19 Sep 2012 23:37:53 +0200 |
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How long the PCB have been around stored (hope packed in a proper moisture
proof packaging, or not ?) from Fabrication date to Reflow date ?
When "playng lead free games", the shelf life of PCB (mainly if
multilayer), and moisture entrapped above safe level (maximum acceptable
moisture content, or MAMC)can play a very important role in terms of quality
results (heavy damages).
Plenty of "cadavers" like those in subject are floating above the "RoHS
River"...
Be careful, and I suggest you to strictly follow, the guide lines given by
IPC-1601.
Regards
Gabriele
(from eurolandia, where the "RoHS Rivers" was born :-( )
-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di SALA GABRIELE
Inviato: venerd́ 14 settembre 2012 17.35
A: [log in to unmask]
Oggetto: [TN] R: [TN] Broken Vias
Hi,
- wrong material (not suitable for Lead Free Reflow Temp), poor TgZ, Plated
Holes with poor copper thickness,..... ?
- wrong reflow thermal profile ?
- PCB been too long time on the shelf (moisture entrapped) before Reflow ?
- any bake has been done before reflow ?
Regards
Gabriele
-----Messaggio originale-----
Da: TechNet [mailto:[log in to unmask]] Per conto di Robert Kondner
Inviato: venerd́ 14 settembre 2012 17.18
A: [log in to unmask]
Oggetto: [TN] Broken Vias
Hi,
A small company in the area has a board with two very expensive parts, about
$3K each part. They built 30 boards and had lots of open via connections.
They are getting cross sections now on some bad vias. In addition to many
bad vias there was some board warp. Sorry I don't have any hard numbers on
bad via counts or warp.
These were 10 mil holes in .062 material, a 6:1 aspect ratio, should be
easy. Vias were plugged and plated so they could be used as flying probe
test points.
After reflow assembly the boards were run on a wave machine using a mask
where about 25% of the board was exposed to the wave. Everything lead free.
Question:
Can folks suggest lists of items we can check, measure or inquire into? Any
guesses or ideas as what might be going on?
Thanks,
Bob K.
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