SMT thin sheet IC's?

Sure. It's making them that thin *and durable* that's difficult.

If you're willing to pay the price, one has been able to embed capacaitors and resistors in PCBs for quite some time now. However, the processing steps for making ICs are rather different than those for making PCBs (even with embedded R's and C's), so it's not surprising that even in high-volume/cost-sensitive applications you still see bare dies wire-bonded to a PCB and then glob-topped.

Maybe BGAs with balls top and bottom. ;-)

Best regards, Spehro Pefhany

But how durable does one have to be? Seems the only real issue is temperature. Putting low power ic's inside shouldn't be an issue. Its also not like most people go around bending pcb boards or throwing them against a wall. (being inside should prevent any normal mechanical issues)

I'm not talking about resistors and caps though, I'm talking about complete ic's that are paper thin that side on a inside layer that that is basically just like a normally ic but "flattened" (like a penny in a press). Only thing that chances is the height of the ic but the width and length are the same. The pins are also pressed flat. I imagine the main issue is mechanical integrity rather then electrical... but I doubt in any normal circustances would it be an issue. (maybe in heating it could cause them to break due to warpage.

Think of, say, an LM317 that is about as thin as a piece of paper that you could solder to a pcb. (in this case it might not be a good idea because of the power dissipation)

Basically the idea is to stick many of the ic's in inner layers to make more room on the outside of the boards. You could do this for discrete components to probably. When a board has 60 layers would could put a lot of stuff on the inner layers instead of just wires and resistors and caps. The only thing I'm "changing" here is the thickness. All other things being equal(if they can be done independent of thickness).

As durable as you need it. Sometime just meeting basic ambient temperature and vibration specs is an issue.

Ambient temperature is an issue for starters.

The main problem is you have to get the bonding wires out. That means either BGA or COB type wire bond. Both require small but significant (and varying) height over and above the silicon. This does not lend itself well to being wedged between glued between two bits of fibreglass.

Boards expand and flex all the time, and being wedged between two fibreglass layers is not exactly a non-hostile environment.

In fact I've actually done it before - sort of. It's possible to "embed" components in enclosed "cutouts" of a PCB. For example, you might have a large cutout say three quarters the way through the board and then mount the conventional IC (BGA, TQFP, COB etc) inside the cutout. That way you get zero height above the PCB. I did this on a project once for very specific reasons and it works very well. This requires an extra routing step at the PCB manufacturing level on whatever layers need the "cutout". PCB packages have a dog of a time supporting it too.

Dave.

I imagine that the idea could be improved to make it work well. The main point is if it is possible. The only issue, really, is if the thickness can be made small enough. I do not know the minimum thickness that silicon has to be substrate have to be. But if it can be small enough then there should only be technical problems that I'm sure can be overcome.

e.g., your issue with the ambient temperature is probably not an issue. For one, only devices of very low power consumption could be used this way(if heat is an issue) and it can be sandwiched between thermal pads on each side that have "vents" to the outer layers to a heat sink if needed.

I don't know all the issues and any of the solution but just an idea. Seems like a feesible idea though but might require a some research. I'd imagine that the benefit is worth it? (would simplify routing, reduce size, maybe electrical benefits, maybe cheaper ic's(less packing material). Although I suppose it would increase pcb fabrication complexity but probalby not much?

Jon

Yes. But unless they are also small (in area) they become fragile.

If you have an RFID passport, there is a 0.2x0.2mm chip embedded in the flexible plastic page. That chip is about

Kind regards,

Iwo

yes, but if they are embedded in the pcb then its not as big a deal. (even if they sit on top of the pcb then its probably not a huge deal) It really depends on how fragile they are which I have no idea but my hunch is that in

This is essentially the same idea but the package is the pcb itself(And its not all that flexible).