Chris, I passed on this the first time because I wasn't sure if you were asking a
design question or an assembly acceptance question.  Assuming assembly acceptance (or
design, for that matter), the issue is any requirement for minimum electrical
clearance.  Minimum electrical clearance is defined in IPC-2221 Table 6-1 and is
dependant on voltage characteristics.

While IPC-A-610B doesn't specifically state the obvious for chip component minimum
electrical spacing, one of the "overhang" requirements for Gull Wing Leads (Fig
10-43) does address "All classes shall not violate minimum conductor spacing . . .".
Several other areas in IPC-A-610B also refer to terminations not violating minimum
electrical clearance.

IPC-A-610 is in revision, and if you feel specific criteria relating to this is
important for surface mount components also, I invite you to submit a comment on
IPC-A-610B Chapter 10 Surface Mount Assemblies to add a note to the lead-in paragraph
or each specific section that component lead or termination area overhang shall not
violate minimum electrical clearance.

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>>> Chris Ball <[log in to unmask]> 10/13/98 03:57PM >>>
Ok then, can anyone enlighten me slowly? Lemme rephrase it a bit....

1206 resistor pads are 1.8 wide. The body is 1.8 max wide. IPC-A-610B,
class 2 says it's acceptable as long as you have 50% overlap of widths...
so it can move .9 either side... so that's a box 3.6 wide that is ok...
right so far? So if two 1206 resistors are side by side, 3.6 apart, and
each part is shifted worst case, they touch. Is that an acceptable
condition per IPC-A-610B, class 2? Or does it mean the parts have to be
spaced further than 3.6 in order to insure that your board is
manufacturable per IPC-A-610B, class 2? Or does anything mean anything
anymore? C'mon y'all....Jo-Ann?... Gary?... Abdulrahman?...

Thank you in advance for all your help ;-)
-Chris-

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