Kevin Di Tondo ([log in to unmask]) asked:

I am intreseted [sic] in finding out how other companies are doing
modifications to fine pitch SMT devices.  What type and gauge of wire?  What
they are holding the wire on the PWB with? ect. Is there a standard that
covers these topics?  Any tips that could be supplied would be much appreciated.

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Kevin this is a really big secret, but if you promise not to tell a soul:

I believe that the designer has not yet been born who can totally avoid the
need for wires, at least in the prototype phase.

Some companies end up trying to ship product with these little wires
hanging on them. We try hard not to. As Bart Simpson would say, they suck.

If you have a wire connection to a "lifted" gullwing lead, it will likely
break the first time it makes any physical contact with objects more
massive than a fly (asuming it miraculously can be desoldered and lifted up
without breaking off at the plastic mold margin). If this is abolutely
necessary, suggest you apply epoxy to the lifted lead and its neighbor
after you have soldered and cleaned as required.

Any manufacturing or quality type will tell you wires are terrible for
reliability, and most customer standards either prohibit them or place
restrictions on the number and the type of solder connection allowed (such
as they must be soldered into a PTH, which may be nigh on to impossible).
As I recall, Bellcore won't accept any wire with a lap connection, which is
what you may have to use for an SMT device.

That being said, use the smallest wire you can. 30 AWG wire is 0.010" dia,
which might be as big as your pad. Avoid silver plated (most wire-wrap wire
is) wire; silver tends to result in dendritic migration. Avoid
cyanoacrylate adhesives, they will affect SIR readings. Kynar
(polyvinylidene fluoride) will melt at normal soder temperatures, so be
careful not to let Kynar insulation run adjacent to any lead which will
later be soldered or re-heated.

Try shaming the designer into a quick respin, and wave your arms wildly as
you tell them how ugly the board will be with these little wires running
over the board, just waiting to break and fall off.

We use (under duress) a wire made by a company called:

Preleg
PO Box 1824
Englewood, FL 34295
813-475-6565

p/n 305321 250 ft spool 32 AWG wire

Preleg wire has a thermoset adhesive coating, and they sell a special
low-temp iron with a slotted tip. When you route the wire, the iron can be
used to tack the adhesive coating to the PWB, then you can run the tip down
the length, and it adheres to the PWB surface nicely leaving minimal
residual.

You might be able to use a regular low temp iron, but it would make a mess
of the tip. Theirs works well.

Get yourself an artistic touch-up person, let them practice, and good luck.

Hit delete now, and remember you are sworn to secrecy. And I like
appreciation, especially when accompanied by cash payments. ;-)

Jerry Cupples
Interphase Corporation
Dallas, TX