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Date: | Tue, 30 Jul 1996 12:10:34 -0600 |
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Nancy,
Fab requirements are probably getting tighter (we spec 6.45 micrograms/in2 NaCl
for PCBs which is/was Bellcore) because assembly outgoing requirement per
J-STD-001A 8.3.2 is 1.56 micrograms/cm2 NaCl (or 10.06 micrograms/in2 NaCl)
ionic residues, same as IPC-RB-276.
Specifying a tighter cleanliness standard for PCBs gives the assemblers
a guardband. PCB suppliers should not have a problem meeting the tighter
cleanliness spec if the PCBs go through a final cleaning prior to packaging and
shipping. We've been at 6.4 for years without having any complaints from our
suppliers, our PCBs typically come in the 2 - 4 microgram/in2 NaCl.
My opinion of checking prior to Entek coating is that it's not necessary. A
cleaning and microetch is part of the standard Entek process, so any residual
contaminants on a PCB should be cleaned off in the Entek process. Others might
have a different opinion.
Tracy Tennant
Micron Technology
[log in to unmask]
30-JUL-1996 09:49:48.21
>From: [log in to unmask]
>To: [log in to unmask],[log in to unmask],STHUMMEL,TTENNANT,MIKEPARRY
>Subj: Fab-Ionic Contamination
>
>Dear Technet,
>
>I have a question about the ionic contamination limits stated in
>the IPC-RB-276.
>
>Reference to IPC-RB-276 Section 3.13.3, it is specified the
>resistivity shall not be less than 10.06 micrograms/sq.inch of
>sodium chloride.
>
>I have discovered that many OEM's are requiring this to be 6
>micrograms/sg. inch.
>
>Is this left over from the Mil-Spec days?
>
>Also
>
>Should boards that are checked before Entek Application be
>required to be 6 micrograms per sq/inch as well?
>
>
>Thanks,
>
>
>Nancy Nelson
>Dell Computer
>[log in to unmask]
>
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