Why is this not the same as the 2832 - .23. Same connector used on both.
Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of SUBSCRIBE TechNet
Rich
Sent: Tuesday, September 25, 2001 2:16 PM
To: [log in to unmask]
Subject: Re: [TN] White Immersion Tin


Some of the advantages:

--The amount of solder applied to the PCB is controlled to a degree that
can not be attained with HASL processing.
--Flatness of the finished surface mount pads is far superior to HASL.
Essentially, the surface is as flat as the copper.
--Fiducials are always in GREAT condition and very vision friendly
--works with a lead-free process
--finished PTH internal diameters are more accuratly controlled (works
great with press-fit connectors)
--EMI and ESD functions were improved as the surface of the contact areas
were very flat.
--Wave solder processing is not affected

Some areas to be critical:

--Be sure your PCB fabricator is capable of adequately cleaning the PCB
during fabrication.  The chemicals used in Immersion White Tin (IWT) will
discolor and continue to consume the copper, under the soldermask.
--Add a means of thickness measurment to your fabrication procedure (SERA
testing)  The minumum recommended thickness (Omikron Immersion White Tin
from Florida CirTech) for the plating is 0.65 microns.  Read the test
results from their web page.
--Solder wetting will be different.  We changed from AIM 293+ to AIM NC251
to improve the wetting to the pads and devices.  We have test results to
support the improved wetting characteristics.
--There is a REDUCED shelf life (about 6 mos.) for PCB's exposed to
atmosphere.

We have seen reductions in solder related defects since changing to IWT.
The overall change has been good for us.

I would reccommend this process to anyone.

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