31–40 of 146 posts
Earlier quoted context omitted.
You could (in theory) put the tape over a circuit board and place components on tape and the circuit would function. It would not short circuit because it only conducts on the z-axis (up and down) not between things on the surface.
I don’t quite get how that’s useful.
Earlier quoted context omitted.
You could (in theory) put the tape over a circuit board and place components on tape and the circuit would function. It would not short circuit because it only conducts on the z-axis (up and down) not between things on the surface.
I don’t quite get how that’s useful.
The prowess of materials science in companies like 3M and Dupont never ceases to amaze me. Just when I think I've seen it all with fiberglass tape and kapton tape...
Their "prowess" saw DuPont give cigarettes laced with new toxic chemicals they made to their employees to test the chemicals effects. Every human on earth has Dupont chemicals in their blood that will never go away, but accumulate over the course of our lives. These are "forever chemicals" that never break down. When you die you pass them on. They are in the animals you eat, in the beverages and water you drink, they…
This is sometimes used to connect rigid touch panel electrodes (on glass) to flex cables, bypasses having to do lots of soldering…
For anyone looking for the interesting numbers: Insulation resistance: 3.4 x 1014 ohms/square Contact resistance: Direct link to datasheet: https://multimedia.3m.com/mws/media/66235O/3m-electrically-c...
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.
What does that mean?
Imagine a tiled surface, where the tiles are conductive but the grout is not. So you have islands of conductive material which don't connect to each other. If you shrink that very small, and make it flexible and sticky, it's useful: Suppose you have a glass LCD panel, like the kind used in clocks and watches. The traces are indium-tin-oxide (ITO), on the glass. This is fiendishly difficult to connect to, it doesn't t…
Earlier quoted context omitted.
You could (in theory) put the tape over a circuit board and place components on tape and the circuit would function. It would not short circuit because it only conducts on the z-axis (up and down) not between things on the surface.
I take it the tape would go in the middle between the circuit board and components?
Let me see...
"place the tape on a circuit board and place components on the tape"
A while back I invested in 3M because it's a company that makes so many amazing and industry leading products and I thought they'd do well. A couple years later and the stock is just lagging. I guess they're dragged down by their environmental lawsuits these days. As a human, I'm appalled at their environmental track record but as an engineer, wow they really do so many things so well.
The relevant question isn't whether they make great products, but whether their stock is undervalued.
We in the tech world are used to "great products" -> "stock price always goes up", but in the "real world" there's no reason for that to be true. "Stock price goes up" should, from an efficient-markets PoV, reflect new information.
A while back I invested in 3M because it's a company that makes so many amazing and industry leading products and I thought they'd do well. A couple years later and the stock is just lagging. I guess they're dragged down by their environmental lawsuits these days. As a human, I'm appalled at their environmental track record but as an engineer, wow they really do so many things so well.