4 ms·

I agree there has got to be a better way to select projects than random. I find it hard to think of an objective and fair critera, but something involving a mix

I agree there has got to be a better way to select projects than random. I find it hard to think of an objective and fair critera, but something involving a mix of effort, research quality, and value to the community would be good. The requirement to use caravel I don't think is overly malicious, but all I heard was "we want to see how people use it". I don't know the reason it's not optional this shuttle run, but I figure it could become optional on future runs. (can't say for sure though.) Also, normally beggars can't be choosers and that's a reasonable take -- but this is kind of different... Preparing your project for submission is a ton of work and users are not being told what to expect very clearly.

octoberfranklin 6y ago
> I agree there has got to be a better way to select projects than random. Provably random? It really seems like "random" is just a way of saying "we're not going to discuss our decision process". > The requirement to use caravel ... but all I heard was "we want to see how people use it". That makes no sense. I'll give them credit for one thing: the way they're doing the WLCSP packaging far-backend run is very slick and cool. Ordinarily WLCSP packaging costs a fortune, and you have to run your own boat of wafers from the MPW to get it. By forcing everybody to use WLCSP with the same pinout EVERYBODY gets this cool option at a reasonable price. But they could very easily have simply said "your UBM layer must be identical to the Caravel padframe's UBM layer" (UBM is the layer that says where the top level of chip metal interfaces with the Under Bump Metallization of the WLCSP package). Basically just say you pins have to be in the same place as Caravel but you don't need to use the rest of it.
- baybal2 6y ago
  WLCSP may not be the best option for everything of course
- ohazi 6y ago
  > Ordinarily WLCSP packaging costs a fortune Compared to what, a bare die? WLCSP is usually cheaper than plastic packages... Edit: Maybe that's only true in volume? I guess throwing a handful of dies on a wirebonder is easy compared with designing and fabbing the interposer, and who cares if the plastic costs a few cents more.
  - octoberfranklin 6y ago
    WLCSP unit cost is very low, but there is a very high fixed cost. Also WLCSP packaging must be done a wafer-at-a-time. With an MPW, you don't get a whole wafer of your chips -- they cut up the wafer and send the chips with your design to you, and the chips with other peoples' design to the other people. So ordinarily on an MPW if you want WLCSP, you have to pay the fab to run a whole second "boat" of wafers just for you, so those wafers can be run through the packaging process before they are cut up. This often costs more than the MPW booking does!

octoberfranklin 6y ago

> I agree there has got to be a better way to select projects than random. Provably random? It really seems like "random" is just a way of saying "we're not going to discuss our decision process". > The requirement to use caravel ... but all I heard was "we want to see how people use it". That makes no sense. I'll give them credit for one thing: the way they're doing the WLCSP packaging far-backend run is very slick and cool. Ordinarily WLCSP packaging costs a fortune, and you have to run your own boat of wafers from the MPW to get it. By forcing everybody to use WLCSP with the same pinout EVERYBODY gets this cool option at a reasonable price. But they could very easily have simply said "your UBM layer must be identical to the Caravel padframe's UBM layer" (UBM is the layer that says where the top level of chip metal interfaces with the Under Bump Metallization of the WLCSP package). Basically just say you pins have to be in the same place as Caravel but you don't need to use the rest of it.

baybal2 6y ago
WLCSP may not be the best option for everything of course
ohazi 6y ago
> Ordinarily WLCSP packaging costs a fortune Compared to what, a bare die? WLCSP is usually cheaper than plastic packages... Edit: Maybe that's only true in volume? I guess throwing a handful of dies on a wirebonder is easy compared with designing and fabbing the interposer, and who cares if the plastic costs a few cents more.
- octoberfranklin 6y ago
  WLCSP unit cost is very low, but there is a very high fixed cost. Also WLCSP packaging must be done a wafer-at-a-time. With an MPW, you don't get a whole wafer of your chips -- they cut up the wafer and send the chips with your design to you, and the chips with other peoples' design to the other people. So ordinarily on an MPW if you want WLCSP, you have to pay the fab to run a whole second "boat" of wafers just for you, so those wafers can be run through the packaging process before they are cut up. This often costs more than the MPW booking does!