Just last week there was an issue someone had with LED's working on cards
that were just reflowed, then shortly after, failing. The failure rate was
quite high.
Can that person reply as to their remedial action ??? Was the profile temps
reached higher than what the leds were designed to withstand ??
Regards
TDK
-----Original Message-----
From: Matthew Lamkin [mailto:[log in to unmask]]
Sent: Wednesday, October 06, 2004 1:04 AM
To: [log in to unmask]
Subject: Re: [DC] Lead-Free Fab_notes
With the increase in reflow temperatures, I would imagine that you will have
to check all your components can handle the new higher temperatures.
I have seen some expand through heating at levels near the top of their
permitted temp, let alone going beyond it.
The lead free substitutes that I am being offered, while may make for a far
flatter finish than HASL etc, are not very good at being resoldered during
rework, pads may have to be heated up more, so if there is a component
fitted that is liable to be replaced during the boards life, it may pay to
increase it's pad sizes slightly to increase adhesion to the laminate
(unfortunately that also has the consequence of making more solder to heat
up).
Matthew Lamkin.
-----Original Message-----
From: Fred Dark [mailto:[log in to unmask]]
Sent: Monday, October 04, 2004 6:00 PM
To: [log in to unmask]
Subject: [DC] Lead-Free Fab_notes
Dear Designer Council, I'm looking to get some information on "Lead-Free"
technology... from a PCB designers point of view, what would I have to do
different for design and documentation... how would my fabrication notes
change for this technology... For a standard Fr-4 material, would this have
to be different... along with finishes and etc... I know there is a lot of
manufacturing issues with solder paste, solder temp. and more, but from a
designers point of view, what will I have to do different... I'm reading up
on the technology, but I'm not seeing what to do as far as from a designers
point of view... Can someone point me in the right direction for notes,
books from a designers point of view... and what ever other info that I
would need to know...
Thank's as always, Fred Dark Jr.
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