3M tape with anisotropic z-axis electrical conductivity

This stuff is rad. I took a class on hardware implants with Joe Fitz a couple years back—on the heels of that wholly unsubstantiated Bloomberg article about China embedding rice grain-sized hardware implants into Supermicro motherboards that magically found their way only to select F100s and gov’t agencies—where we made a PCB to interface an ATtiny85 to an unpopulated UART header on some IoT device but instead of soldering it down we just taped it with this.<p>(The UART provided a root shell and enough power to “boot” the ATtiny which simply waited a few seconds and then ran some commands to initiate a reverse shell to a server under our control every time the device was powered on. Thanks to this tape and the device’s tool-less case (and convenient unpopulated header with space around it), it was enlightening how trivially easy it’d be to develop and deploy such an implant to an operating device (with the caveat that I wouldn’t consider the connection robust enough to survive transport).<p>It’s also useful to connect SMD EEPROMs to unpopulated&#x2F;desoldered pads for testing without installing a socket.

A while back I invested in 3M because it&#x27;s a company that makes so many amazing and industry leading products and I thought they&#x27;d do well. A couple years later and the stock is just lagging. I guess they&#x27;re dragged down by their environmental lawsuits these days.<p>As a human, I&#x27;m appalled at their environmental track record but as an engineer, wow they really do so many things so well.

For anyone looking for the interesting numbers:<p><pre><code> Insulation resistance: 3.4 x 1014 ohms&#x2F;square Contact resistance: &lt; 0.3 ohms Minimum gap: 0.4mm Minimum overlay area: 3.2mm^2 </code></pre> Direct link to datasheet: <a href="https:&#x2F;&#x2F;multimedia.3m.com&#x2F;mws&#x2F;media&#x2F;66235O&#x2F;3m-electrically-conductive-adhesive-transfer-tape-9703.pdf" rel="nofollow">https:&#x2F;&#x2F;multimedia.3m.com&#x2F;mws&#x2F;media&#x2F;66235O&#x2F;3m-electrically-c...</a>

This stuff confused the hell out of me as a 6-yr old electronics hobbyist (read unskilled-tear-downer). Took apart a non-functioning lcd calculator. Everything looked normal, except the lcd display itself was just pressed onto a rubbery tape like thing which seemed to be stuck to a line of pads in the pcb.<p>I expected a flex cable connecting the lcd to the PCB but couldn&#x27;t find one. I &#x27;knew&#x27; rubber was an insulator, so no matter what that rubbery thing was (I guessed it was simply a spacer) it wasn&#x27;t the connection between the two.<p>Didn&#x27;t learn about the existence of z-tape for another decade or so and immediately the light bulb in my brain flashed, solving a childhood mystery.

The prowess of materials science in companies like 3M and Dupont never ceases to amaze me. Just when I think I&#x27;ve seen it all with fiberglass tape and kapton tape...

Years ago I had the idea to use this tape to make solder-free PCB kits to teach electric circuits (the tape would connect the chip pins to the board, without shorting sideways). I bought a roll, and printed some boards for LEDs and 555 timers and such.<p>Unfortunately it didn&#x27;t make reliable contact for the chip pins unless you were constantly pushing down on it. As I recall the datasheet states as much. That seems like a solvable material science problem, but alas perhaps not valuable enough.

Ben Krasnow used this for his DSKY replica [0] - its a very interesting product.<p>[0] - <a href="https:&#x2F;&#x2F;youtu.be&#x2F;Z2o_Sp2-aBo" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;Z2o_Sp2-aBo</a>

The first place I saw this stuff was a presentation by one of the people behind Chibitronics. Along with copper tape really useful for building up circuits on paper. Not sure if they still use it in any of the products but still pretty cool: <a href="https:&#x2F;&#x2F;chibitronics.com" rel="nofollow">https:&#x2F;&#x2F;chibitronics.com</a>

This is sometimes used to connect rigid touch panel electrodes (on glass) to flex cables, bypasses having to do lots of soldering…

What does that mean?

If y&#x27;all have never been on McMaster-Carr, you are in for a treat: <a href="https:&#x2F;&#x2F;www.mcmaster.com" rel="nofollow">https:&#x2F;&#x2F;www.mcmaster.com</a><p>All kinds of stuff like this can be explored with a pretty decent UI.

I went to look at this expecting it to also have excellent thermal conductivity (due to the low resistance z-axis conductivity through silver particles). To my surprise, it does not. The published range is 0.16-0.20 W&#x2F;mK, which is pretty much what you get for most tape products.<p>We use specialized thermally conductive tapes in a range &gt;= 1 W&#x2F;mK. I am always looking for interesting developments in this domain.

Unless I&#x27;m misreading this, it&#x27;s $19.78 &#x2F; yard for 4&quot; wide size at digikey.<p>If the link doesn&#x27;t work (lots of tokens in there) try searching for &quot;9703 3M tape conductive&quot; as a starting point.<p><a href="https:&#x2F;&#x2F;www.digikey.com&#x2F;en&#x2F;products&#x2F;detail&#x2F;3m&#x2F;9703-4-X36YD&#x2F;6820572?s=N4IgjCBcoOw1oDGUBmBDANgZwKYBoQB7KAbRBjAA4AWANhAF0CAHAFyhAGVWAnASwB2AcxABfAmGrxoIZJHTZ8RUiGoBmAAz0mINh279hYiTHoy5C3AWKQyAJgCsDrdUYt2kLr0Ejx4OAiyqJhWyrYgamAadhoAnG66Hl6GvhKxaoEWIUo29hrULgl6ngY%2BxqrpmcGK1ipq6g60GkVJpUZ%2BtLHx5tWhuRGUsZTDLfre7QQwGs098tm14WrDDo6jJeOp4BowdlVzNWFkBQ6uOsXJZX5gQ91IvTkqzWetG%2BUAtBCzlg-h14x%2Bb1cX3mhxAQ0i-wIbwce2%2BCzItAgDFEfl24ViUwyyKAA" rel="nofollow">https:&#x2F;&#x2F;www.digikey.com&#x2F;en&#x2F;products&#x2F;detail&#x2F;3m&#x2F;9703-4-X36YD&#x2F;6...</a>

Could this be used for CPU (or some other truckload-of-pins chip) &quot;reballing&quot;? Does it do well under a bolted-on radiator &#x2F; pressure plate?<p>For instance, many old Playstation 3 systems go faulty because of the poor quality solder on the CPU&#x2F;GPU that tends to crack over time. Being a normie, it&#x27;s really hard to fix something like that at home. But this tape seems like it could save the day.

What&#x27;s Z-axis on this tape? is it thickness?

Oof, a roll of this stuff is ~$180

Would be extremely useful to get an explanation of what 3M means is the &quot;Z-axis&quot; of the tape. Along the tape plane? Across the tape plane? Through the tape plane?<p>I can see uses for all, but <i>how</i> you&#x27;d apply it would certainly differ if depending on which one is Z....

It&#x27;s been pretty entertaining to watch the stocks of this stuff on Amazon dwindle minute by minute

Neat. Elastomeric materials like that are widely used, made from alternating insulating and conductive layers. They need external compression. An adhesive tape is a clever variation.

Is there a less technical term for anisotropic? Polarized?