Graham
how long you immerse the PWB in "hot" IPA/DI mixture? what is "hot"?
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Graham Naisbitt
>Sent: Friday, August 09, 2002 10:20 AM
>To: [log in to unmask]
>Subject: Re: [TN] Board cleanliness
>
>
>Hi Bev and Susan,
>
>Permit me a W O A H!
>
>This is such a misleading spec. To say that something should be cleaned
>to a level of less than 1.5 microgrammes / cm2 also means that it is
>acceptable to leave UP TO 1.5 microgrammes of NaCl equivalence on every
>square cm of your assembly! But if you are manufacturing to modern
>fine-line, fine-pitch and components to suite....then that level will
>almost certainly be too high.
>
>I have many customers who have, as a result, imposed their own empirical
>cleanliness value at something less than 0.02microgrammes/cm2 for Class
>3 assemblies. As has been stated already, the ionic extract cleanliness
>test is/was only intended to be used for process monitoring. The
>Pass/Fail can and has got a lot of people into troublesome problems.
>
>I also register concern at the use of "hot" ipa / water mixture - safety
>issues apart, there has been a good deal of research demonstrating that
>prolonged immersion in such a solution can induce the bromine flame
>retarder to rise to the surface of the board and....this is a problem!
>Would you care to comment?
>
>Regards Graham Naisbitt
>
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>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
>> Sent: Friday, August 09, 2002 03:44
>> To: [log in to unmask]
>> Subject: Re: [TN] Board cleanliness
>>
>>
>> Patrick,
>> Susan mentions a standard (US military MIL-P-55110E), but I
>> would like to point out another standard - GR-78 CORE from
>> Telcordia, which is used extensively in the
>> telecommunications industry. It requires that the finished
>> bare board cleanliness be less than (or equal to?) 1
>> ug/square centimeter. For you Americans, that's 6.5
>> ug/square inch. The standard goes on to state that for a
>> finished assembly that has gone through a wash cycle that the
>> circuit pack have a SEC value less than (or equal to?) 1.5
>> ug/square centimeter. There is no standard for no-clean
>> boards, but then there are other criteria that the no-clean
>> flux/solder paste must meet first
>> - copper mirror, halide ion spot test, SIR and
>> electromigration. Some companies still require a fluoride ion
>> spot test and SIR/EM testing of possible mixtures of wave
>> soldering fluxes/solder pastes/cored wires. And some
>> companies have set process indicator levels for SEC testing
>> of circuit packs manufactured with no-clean fluxes,
>> especially for wave soldering. Note, I said "process
>> indicator", so don't bring fire and brimstone down on me,
>> fellow Technetters! :)
>>
>> regards,
>> Bev Christian
>> Research in Motion
>>
>> -----Original Message-----
>> From: [log in to unmask] [mailto:[log in to unmask]]
>> Sent: August 8, 2002 4:41 PM
>> To: [log in to unmask]
>> Subject: [TN] Board cleanliness
>>
>>
>> Hi Technetters,
>>
>> I would like to know how to specify board cleanliness on the
>> Fab drawing. We use class 3 boards. Does it make any
>> difference on cleanliness standard? Is it OK to ask for
>> cleanliness test results/reports shipped with every lot?
>> Which department in a company should be responsible for this
>> board cleanliness issue, R&D, Quality or Production?
>>
>> Thanks in advance to everyone sharing this information.
>>
>> Best regards,
>>
>> Patrick
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