mikep
Well-known member
Has anyone noticed how SMD reflow mounting footprints for a given package can vary greatly from manufacturer to manufacturer? I went thru my libraries and found a half dozen different footprints for sot23. I guess it doesnt matter a whole hell of a lot, but aren't these things supposed to be standardized?!
I'm having a bit of a problem with the sot363 package in general. my surface mount contractor is telling me my footprint in sub optimal for the micr0 c0mmercial quad-diode in this package, but I just checked it and it is dead-on with what NXP published. it has worked for me in the past with other parts in this package. any input greatly appreciated.
excerpted from a nice white paper I found on AVX's website:
"Pad Design. Solder fillet shape and size is ultimately
determined by the pad design. Unfortunately there is a
profusion of recommended pads by component manufacturers,
government agencies, industry associations,
and component users to name a few; but which has
“THE PADS” is the question. Pads recommended by
government agencies result in bulbous, easy-to-see
solder joints that are neither reliable nor manufacturable.
Excessive solder increases soldering defects
(tombstoning) and makes components more sensitive to
handling damage (cracks). Remember when you sit
down for an IRS audit and the agent says, “I’m with the
government and I’m here to help you.” Would you
believe him?"
See:
http://www.avx.com/docs/techinfo/smzero.pdf
IPC publishes at least 3 sets of footprints for each package. yeesh.
mikep
I'm having a bit of a problem with the sot363 package in general. my surface mount contractor is telling me my footprint in sub optimal for the micr0 c0mmercial quad-diode in this package, but I just checked it and it is dead-on with what NXP published. it has worked for me in the past with other parts in this package. any input greatly appreciated.
excerpted from a nice white paper I found on AVX's website:
"Pad Design. Solder fillet shape and size is ultimately
determined by the pad design. Unfortunately there is a
profusion of recommended pads by component manufacturers,
government agencies, industry associations,
and component users to name a few; but which has
“THE PADS” is the question. Pads recommended by
government agencies result in bulbous, easy-to-see
solder joints that are neither reliable nor manufacturable.
Excessive solder increases soldering defects
(tombstoning) and makes components more sensitive to
handling damage (cracks). Remember when you sit
down for an IRS audit and the agent says, “I’m with the
government and I’m here to help you.” Would you
believe him?"
See:
http://www.avx.com/docs/techinfo/smzero.pdf
IPC publishes at least 3 sets of footprints for each package. yeesh.
mikep