3 ms·

For anyone looking for the interesting numbers: Insulation resistance: 3.4 x 1014 ohms/square Contact resistance: < 0.3 ohms Minimum gap: 0.4mm

by nomel 5y ago

For anyone looking for the interesting numbers: Insulation resistance: 3.4 x 1014 ohms/square Contact resistance: < 0.3 ohms Minimum gap: 0.4mm Minimum overlay area: 3.2mm^2 Direct link to datasheet: https://multimedia.3m.com/mws/media/66235O/3m-electrically-conductive-adhesive-transfer-tape-9703.pdf https://multimedia.3m.com/mws/media/66235O/3m-electrically-c...

smegsicle 5y ago
so the 3.4e14 is resistance along the tape, and .3 is vertically, right?
- mensetmanusman 5y ago
  Yes, in plane (XY), it is many orders of magnitude more resistive than out of plane (Z-axis).
  - nuccy 5y ago
    Interesting, how "designed for EMI shielding" (as written on the product page) works then. The charges in the shield should be able to move not just in Z but also in X&Y to actually work as a Faraday cage.
    - nomel 5y ago
      > Z but also in X&Y to actually work as a Faraday cage. The x-y could be done by the contiguous ground above and below the tape. For example a can/shield stuck onto a ground region of a PCB, with signal lines going up nearby. I imagine this is mostly used with flex PCBs.
crmd 5y ago
Thanks. This is exactly what I was looking for, and it was annoying this wasn’t in the specification or details section.
db48x 5y ago
I think you mean 3×10¹⁴ ohms/square.
kurthr 5y ago
What people should also know is that every single display, and that includes every single cell phone touch screen has ACF (Anisotropic Conductive Film) in them. They aren't the same contact adhesive as this 3M film, and some are moderately expensive (e.g. >$0.25/inch @1mm width) for those displays, which is at least comparable (>10%) to the display ICs attached to them. Why is so much ACF used? Because it is the most cost effective and compact way to connect dissimilar high density connections from one substrate to another. Displays typically require thousands of connections so you're looking at linear densities of 1 contact per mil (~25um) with resistances measured in ohms (for less than 0.01mmsq). The reason that IC packages (internally wire bonded or electroplated CSP) don't use ACF is a combination of cost, self alignment (solder pulls it into place), and much lower resistance. The way that almost all of these ACFs are made is embedding conductive beads (often spherical of controlled diameter) which can compress when the adhesive is pressed/bonded to the two substrates. If the aerial density of the beads is right, you'll only get a few beads in contact and none will short any neighboring contacts. For displays the ACF material is typically a ~25um thick B-stage epoxy, which is tacked down and then "snaps" when heated and compressed permanently pulling together the two contact regions and compressing ~10um gold coated polystyrene balls between gold "fingers" on each glass/PCB/COF/COP side after the epoxy flows. 3M tried to get into these higher end ACFs, but now it's mostly Japanese and Korean suppliers.
Sporktacular 5y ago
To clarify, those figure are after bonding right? I understand that means it must be heated and compressed between conductors to reach those values.

by nomel 5y ago

smegsicle 5y ago

so the 3.4e14 is resistance along the tape, and .3 is vertically, right?

mensetmanusman 5y ago
Yes, in plane (XY), it is many orders of magnitude more resistive than out of plane (Z-axis).
- nuccy 5y ago
  Interesting, how "designed for EMI shielding" (as written on the product page) works then. The charges in the shield should be able to move not just in Z but also in X&Y to actually work as a Faraday cage.
  - nomel 5y ago
    > Z but also in X&Y to actually work as a Faraday cage. The x-y could be done by the contiguous ground above and below the tape. For example a can/shield stuck onto a ground region of a PCB, with signal lines going up nearby. I imagine this is mostly used with flex PCBs.

crmd 5y ago

Thanks. This is exactly what I was looking for, and it was annoying this wasn’t in the specification or details section.

db48x 5y ago

I think you mean 3×10¹⁴ ohms/square.

kurthr 5y ago

What people should also know is that every single display, and that includes every single cell phone touch screen has ACF (Anisotropic Conductive Film) in them. They aren't the same contact adhesive as this 3M film, and some are moderately expensive (e.g. >$0.25/inch @1mm width) for those displays, which is at least comparable (>10%) to the display ICs attached to them. Why is so much ACF used? Because it is the most cost effective and compact way to connect dissimilar high density connections from one substrate to another. Displays typically require thousands of connections so you're looking at linear densities of 1 contact per mil (~25um) with resistances measured in ohms (for less than 0.01mmsq). The reason that IC packages (internally wire bonded or electroplated CSP) don't use ACF is a combination of cost, self alignment (solder pulls it into place), and much lower resistance. The way that almost all of these ACFs are made is embedding conductive beads (often spherical of controlled diameter) which can compress when the adhesive is pressed/bonded to the two substrates. If the aerial density of the beads is right, you'll only get a few beads in contact and none will short any neighboring contacts. For displays the ACF material is typically a ~25um thick B-stage epoxy, which is tacked down and then "snaps" when heated and compressed permanently pulling together the two contact regions and compressing ~10um gold coated polystyrene balls between gold "fingers" on each glass/PCB/COF/COP side after the epoxy flows. 3M tried to get into these higher end ACFs, but now it's mostly Japanese and Korean suppliers.

Sporktacular 5y ago

To clarify, those figure are after bonding right? I understand that means it must be heated and compressed between conductors to reach those values.