Hi Hank,
there used to be a european standard in effect, the CECC00802 titled "CECC
Standard Method for the Specification of Surface Mounting Components (SMDs)
of Assessed Quality (1993)." This standard specifies a soldering heat
resistance test for SMDs to be carried through by complete immersion of the
device into 260°C molten solder bath; but go and try finding component
manufacturers who brag that they comply. We are at moment updating our
standards library. I am myself eager to learn what the follow-up of this old
CECC00802 looks like. Please tell me at [log in to unmask] if you want me to
keep you posted. In the light of upcoming "high temperature" lead free
solder alloys, the solder heat resistance of PEMs (thank you for clarifying
the abbr., Stephen) is worth revisiting. By the way, people who have learnt
it the hard way told me that it IS possible to wave solder .5mm pitch ICs,
but this should not be taken as a new trend.
Best regards,
Thomas Ahrens, Memellandstr. 8, D-24598 Boostedt
Tel. ++(49) (0) 4393 97769 e-mail [log in to unmask]
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-----Ursprüngliche Nachricht-----
Von: Stephen R. Gregory <[log in to unmask]>
An: [log in to unmask] <[log in to unmask]>
Datum: Montag, 7. Februar 2000 02:50
Betreff: Re: [TN] Immersion of PEM's in Solder Wave
>In a message dated 02/06/2000 5:54:02 AM Central Standard Time,
>[log in to unmask] writes:
>
>> Could someone tell me what the standard is regarding immersion of PEM's
in
>> the solder wave? Addition comments would be welcome.
>>
>> Thanks
>>
>> Hank
>
>Hi Hank!
>
>I don't think there's any standard out there, it would be dependant on the
>manufactureres recommendations...I wouldn't be suprised that most won't
>recommend exposure to wave soldering. A PEM by the way for those that
aren't
>familiar with that acronym is Plastic Encapulated Microcircuit, or IC's as
>more widely known.
>
>I think that most smaller packages are pretty tolerant to wave solder,
>anything from a SO20 and below. If you start getting larger than than, then
I
>would start to worry.
>
>Of course there should be a good preheat prior to the package hitting the
>wave, and there are design considerations (orientation to the wave,
thieving
>pads etc.) that will reduce defects during the process. But my preferences
>are to do a double-sided reflow on boards that have active components on
both
>sides, rather than expose them to wave solder. That process in my opinion
is
>easier than dealing with epoxy, even if you have to mask the SMT on the
>bottom-side.
>
>-Steve Gregory-
>
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