Stuffing boards with pulled QFP chips
ajp166 at verizon.net
Fri Mar 31 18:28:28 CDT 2017
On 03/31/2017 02:00 PM, Paul Koning wrote:
>> On Mar 31, 2017, at 1:51 PM, allison via cctech <cctech at classiccmp.org> wrote:
>> On 03/31/2017 06:32 AM, David Griffith via cctalk wrote:
>>>> I'm down to the last few P112 boards for sale and am pondering
>>>> another run of them because demand is steady. One of the biggest
>>>> challenges for the last run was getting the QFP-packaged 100-pin
>>>> chips in a state such that the pick-and-place robot wouldn't throw
>>>> a fit about slight differences in lead position. The stuffing house
>>>> insisted that I send them new chips. Pulls, though they looked
>>>> perfectly okay to me, were not acceptable. Does anyone here know
>>>> anything about pick-and-place robots using pulled 100-pin QFPs,
>>>> particularly a stuffing house that can work with such chips and not
>>>> screw up?
>>>>  The now-obsolete super-io chips
>> Is this something that an experienced hand can manually do?
> Yes, definitely. 100 lead PQFP is perfectly doable if the lead pitch is not insanely small. It takes a good fine tip soldering iron (mine is a Weller with a PTS tip), fine solder (preferably real, i.e., 63/37 non-PC solder). Liquid flux is a big help, as is a magnifier and bright light or modest magnification microscope.
> If you have to do a couple of dozen boards this gets very tedious, but for 5-ish it isn't a big deal.
So happens I'm fully equipped on all counts. Including the PTS tip.
However my preference
for years has been the PTA7K (WTCP60) which is 1/4" wide! Gets a few
pins done at a time... ;)
I've not gone over to the Rohs side, most of the solders are not fun to
work with though a
few have very active fluxes and solder aluminium well. So its Kester
44 in 10 and
20 mil (inch mil) diameters.
I've done more than a few AD537 and similar Blackfin CPUs with their 288
BGA package that's
a challenge to pull and replace.
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