[moved] pulse trimming of resistors - availability

[phenol]

I've seen some patents on voltage pulse trimming techniques applicable to thick film resistors that are otherwise buried or inaccessible to laser trim, but never a commercially available source of such equipment.
Does anyone know companies making that?

 

[dick_freebird]

No experience with thick film (like hybrid / MCM) but I
have worked on bringing fuse trim technology to
production (with great technical success, only to be
shafted by parachute-in, parachute-out technical
management).

We did this with only lab grade GPIB power supplies
(or on ATE), for a poly fuse in the micron neck width
range it needed under 100mA and maybe a millisecond
to do the job, and the process is self-terminating in
voltage mode (fuse blows, current stops).

Figure out your reliable fusing (initial, and grow-back
if this is a materials-system possibility) parameters and
see what that suggests as to equipment capability and
form.

Now, a buried resistor mass will be a worst case for
electrical trimming because it has thermal exit in all
directions potentially requiring twice the pulsed power
to reach the material liquidus. Shorter pulse with more
voltage approaches adiabatic fuse heating and helps,
but you may be limited as to max voltage by the other
"stuff" attached to the fuse, this is a trim method "box".

 

[phenol]

we are talking about ruthenium oxide ink printed resistors in the 10s-100s of ohms, unconnected to anything prior to trimming; from what I've heard/read, a series of pulses with progressively increasing energy or packets of tightly spaced pulses are required to do the job.