Álvaro Lopes wrote: > Rene Harder wrote: > >> So here are a few comments where i think we can cut costs. >> > > >> Is 4 mil really necessary? Most fabs go down to 5-6mil as min. >> Trace/Space width. I believe we can find a fab who can make boards with >> 4mil but that require a more precision fabrication process as well makes >> it electrical and optical test absolutely necessary. Although most fabs >> will require an electrical test for board with equal or more than 6 layers. >> > > No, we can live with 5mil. Unless the RF traces require smaller tracks, but > we can overcome that. >
If I'm not completely off we should end up with a trace width around 8-15mil (50Ohms). > >> I think for a prototype a regular chemical or HAL tin finish might be >> sufficient or are the any specific reasons why we need ENIG. >> > > >> I guess 1080 woven-glass with 65% FR4 epoxy laminate is pretty much >> standard everywhere so shouldn't be too difficult to get. About 1078 >> prepreg im not sure, haven't seen it anywhere in the specs so this might >> be only possible within custom specs. >> > > We should get quotes from some manufactures about the prepreg. Actually we > need that to properly design RF. > > >> 140 unique components, that's quite much >> > > I don't think so. There are machines that can handle more than that. > It's not about the handling, It's more related to the cost. Someone has to setup the assembly machine (change reels, setup placements etc.) and if you have a lot of different components you will increase these setup costs. However for a full production series that should not be a big issue because this will be a one time fee averaged over all boards but for a small prototype series this will probably be the main part of the costs. > >> For solder stop mask and silk screen i think they don't make much of a >> difference in production cost usually you have to pay a small setup fee >> for the whole batch if it's not included. >> > > Define 'small' :) > less than 1% of the total board costs. > >> A serious problem are blind and buried vias though. They are our killer >> for any standard specs, if I'm not mistaken they require a huge amount >> of extra steps between every lamination process which is impossible to >> do within standard spec. So best would be to stick to PTH vias if that's >> not possible our cost will be probably more than doubled. >> > > PTH vias present other problems too. We can probably like with PTH though, > but I'd like at least to have microvias for the FBGA. But all this depends on > how we > decide to use the layers. > Microvias are even worse then buried or blind vias those requires special equipment for the fab (laser drills) and a quite complicated process. So i would rather use blind or buried vias! Although microvias will make our live easier then we can embed them into the BGA pads. > >> Just a an example a board with our size, 6 layer, 6 mil Trace/Space, all >> holes platted through, quantity 15 pcs. is about $80 USD/ per board >> (board outline routing is only rectangle though) >> > > > plated through, and filled with insulator or conductor? > all holes are platted through and not tented or filled with anything. > >> For a board with our current specs 8 layer, ENIG, burried and blind >> vias, we would need to get a custom quote (which usually needs a final >> board layout). But i do think Werner's estimation is not far away from >> the real cost so we would end up around $250-300/per board. >> >> At the end, i think we should consider that this will be *only* a >> prototype and not a usable phone, so we don't need a lot of gimmicks >> which are not absolutely required. >> > > Yes, but we should get as close as the "final product" as possible. > I agree, but a prototype is only one step to the final product and supposed to minimize the risk and costs of failures. I doubt that anyone can design a product without prototyping and honestly, I believe that this one will not be the last one for gta02-core. _______________________________________________ gta02-core mailing list [email protected] https://lists.openmoko.org/mailman/listinfo/gta02-core
