Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@...> wrote:
>
> Ah yes, but have you actually _seen_ the resistors (in a picture or
for  
> yourself).
> 
> 'cause, if i rember right, i had a look with a 'scope back than and  
> couldn't see anything between the gap of the apparent electrodes.

Well, no, but I've never seen you but I am pretty sure you exist. ;')

Even the patents say there are resistive elements. I'm not sure what
you expect to see.  What power microscope? As I recall, you'd need an
electron microscope to make out the details of an IC well enough to
pick out single elements of the circuit.

From patent 4,532,530
"A carriage type, bubble jet ink printing system having improved
bubble generating resistors that operate more efficiently and consume
lower power, without sacrificing operating lifetimes. The resistor
material is heavily doped polycrystalline silicon which can be formed
on the same process lines with those for integrated circuits to reduce
equipment costs and achieve higher yields. Glass mesas thermally
isolate the active portion of the resistor from the silicon supporting
substrate and from the electrode connecting points, so that the
electrode connection points are maintained relatively cool during
operation. A thermally grown dielectric layer permits a thinner
electrical isolation layer between the resistor and its protective,
ink interfacing tantalum layer, thus increasing the thermal energy
transfer to the ink."


Same references to an Encad patent improvement on HP cartridges,
referencing resistive elements. Description sounds like you'd not
expect to be able to recognize the resistive elements.

Patent 5,646,660

Steve Greenfield