SMD thick film resistors with exposed film path?

[Dave Moore]

I've been searching high and low but have yet
to find a manufacturer of flat SMD thick film
resistors that either seals them in a clear coating
or alternatively simply reveals the etch pattern
via easily obtainable documentation.

So, before I go to pestering some maunufacturers
for such data, I thought I'd ask here in SED in the
hopes that someone might already have a line on
such animals.


Thanks in advance
Dave Moore

 

[John Larkin]

I've been searching high and low but have yet
to find a manufacturer of flat SMD thick film
resistors that either seals them in a clear coating
or alternatively simply reveals the etch pattern
via easily obtainable documentation.

So, before I go to pestering some maunufacturers
for such data, I thought I'd ask here in SED in the
hopes that someone might already have a line on
such animals.


Thanks in advance
Dave Moore

Try googling "trimmable thick-film resistor"

John

 

[John Larkin]

I've been searching high and low but have yet
to find a manufacturer of flat SMD thick film
resistors that either seals them in a clear coating
or alternatively simply reveals the etch pattern
via easily obtainable documentation.

So, before I go to pestering some maunufacturers
for such data, I thought I'd ask here in SED in the
hopes that someone might already have a line on
such animals.


Thanks in advance
Dave Moore

Oh, the "etch pattern" on most such resistors is a uniform film with a
tiny laser-trim slit. The only really structured resistors I've seen,
with a serpentine pattern, were some 150 megohm things.

John

 

[Dave Moore]

: On Fri, 3 Nov 2006 06:17:34 -0600, "Dave Moore" <[email protected]>
: wrote:
:
: > I've been searching high and low but have yet
: >to find a manufacturer of flat SMD thick film
: >resistors that either seals them in a clear coating
: >or alternatively simply reveals the etch pattern
: >via easily obtainable documentation.
: >
: > So, before I go to pestering some maunufacturers
: >for such data, I thought I'd ask here in SED in the
: >hopes that someone might already have a line on
: >such animals.
: >
: >
: >Thanks in advance
: >Dave Moore
: >
: >
:
: Oh, the "etch pattern" on most such resistors is a uniform film with a
: tiny laser-trim slit. The only really structured resistors I've seen,
: with a serpentine pattern, were some 150 megohm things.
:
: John


Would the slit be perpendicular to the trace?

Thanks for the info.
A lot of the thick film depictions I've seen seem
to imply that they are uniform, which is why my
inquiry was about thick film devices as a uniform
film better serves my purpose.

However I wasn't entirely convinced about
the accuracy of some of the thick film drawings
being that I had recently acquired some TaN
chips which I thought ( due to a graphical depiction)
were *uniform film* types only later to stumble on
more detailed and revealing depictions which
showed that they were actually serpentine:
But of course these were thin film devices.

Thanks for making me feel better about taking the
thick film depictions verbatim.

Thanks again
Dave Moore

 

[John Larkin]

: On Fri, 3 Nov 2006 06:17:34 -0600, "Dave Moore" <[email protected]>
: wrote:
:
: > I've been searching high and low but have yet
: >to find a manufacturer of flat SMD thick film
: >resistors that either seals them in a clear coating
: >or alternatively simply reveals the etch pattern
: >via easily obtainable documentation.
: >
: > So, before I go to pestering some maunufacturers
: >for such data, I thought I'd ask here in SED in the
: >hopes that someone might already have a line on
: >such animals.
: >
: >
: >Thanks in advance
: >Dave Moore
: >
: >
:
: Oh, the "etch pattern" on most such resistors is a uniform film with a
: tiny laser-trim slit. The only really structured resistors I've seen,
: with a serpentine pattern, were some 150 megohm things.
:
: John


Would the slit be perpendicular to the trace?

It's usually an L shape. It comes in from one side, sorta midway
between the end caps, perpendicular to the length of the resistor,
cuts in a ways, then turns 90 degrees and runs some more. The first
part is the coarse trim and the dogleg is the fine.

Some thinfilms can be more limited on ohms/square than thickfilms, so
they may have to do serpentines to get higher ohms. The Vishay metal
foil resistors have very low ohms/sq material, and they tend to have
very complex etch patterns with a lot of cuttable link options.

John

 

[JoeBloe]

Try googling "trimmable thick-film resistor"

Take the path of least resistance.