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I am in the process of setting up a small design laboratory and one of our first projects include the use of a 584-BGA microcontroller. This means that we'd have to use an 8 layer design, something that we have never done before, and we are not aware of anyone who does similar stuff locally in our country. You can imagine how this affects our lead-time.

We are looking to find a way of fabricating

Any idea of what equipment would be used in the fabrication process, from the Gerber file to fully assembled PCB. For clarity, we know that we need a circuit printer with fine-pitch capability, a pick and place machine and a reflow oven. What we don't know is what we should be looking for in all the equipment, save for the pick and place machine.

Arguments against trying to do the PCB assembly ourselves would be very much appreciated.

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    \$\begingroup\$ You need expensive machines to get the required precision for BGA on 8-layer PCB. This is about one hundredth of a mm. You'll have to make a lot of boards to get at break-even. \$\endgroup\$ – Federico Russo Jul 25 '12 at 11:30
  • \$\begingroup\$ @FedericoRusso: Huh? Working with BGAs may not be easy, but my understanding is that most BGAs have balls on a 1 mm grid, so they are easier to place and require less precision than TQFPs with 0.5 mm pitch. \$\endgroup\$ – davidcary Jul 25 '12 at 19:37
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    \$\begingroup\$ @davidcary: a BGA-584 has a 0.8 mm pitch, you need vias between the pads which have annular rings much smaller than those, and positioning a drill has more tolerance than the pads. \$\endgroup\$ – Federico Russo Jul 26 '12 at 6:11
  • \$\begingroup\$ @FedericoRusso: Right, I see now -- positioning is easier, but drilling the holes is much more difficult with BGAs than TQFPs. \$\endgroup\$ – davidcary Jul 26 '12 at 17:23
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Advanced PC boards can only be made by little elves in a hollow tree. It is possible for ordinary mortals to make good enough 2 layer board for hobby or prototype purposes, but even that doesn't make sense unless they value their time very little and not look too hard at the cost of screwups due to not having a solder mask, silkscreen, and the hassle of not having plated thru holes.

Anything beyond basic two layer boards requires elven magic. The elves have spent millions on special trees and are constantly watching the process. Due to the combination of up front cost and special magic, even the elves can only afford to do this by making boards for lots of people to get the volume up and the average cost per board down to less than a pot of gold.

Fortunately the elves have gone high tech and there are now quite a few places on the internet where you can upload Gerber and drill files and receive finished boards usually within a week or two, all without having to dig deep into your own pot of gold. For example, you can get however many boards fit into 75 square inches for $250 at Gold Phoenix. This includes solder mask on both sides, silk screen on one side, of course plated holes, and electrical testing. 8 layers will be more difficult since that is past most place's prototype process, but setting up your own process will be more difficult to.

This is a case where DIY really just doesn't make sense. Are you going to refine your own silicon too?

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    \$\begingroup\$ +1 for knowing about the PCB making elves, most folk think they don't exist... \$\endgroup\$ – Oli Glaser Jul 25 '12 at 12:20
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    \$\begingroup\$ @Oli: Yeah, the muggles apparently can't see them. \$\endgroup\$ – Olin Lathrop Jul 25 '12 at 12:35
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    \$\begingroup\$ @Olin LOL. Quite a humorous way to get the point a cross. Of course the bigger question is why on earth need an 8 layer assembly in the first place \$\endgroup\$ – partoa Jul 25 '12 at 14:26
  • \$\begingroup\$ "even the elves can only afford to do this by making boards for lots of people" - No wonder my last E.L. Fudge cookie was frosted with soldermask... \$\endgroup\$ – Chris Laplante Jul 25 '12 at 15:26
  • \$\begingroup\$ @partoa: Some BGA design guides force you to use 8 layers for larger BGAs. I agree that the bigger question is: So why on earth would you select [digikey.com/product-search/… a part in such a BGA package] when you can get almost the same functionality in QFP package or two that works fine with 4 layers? \$\endgroup\$ – davidcary Jul 26 '12 at 16:45
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You imply "all stages" and this seems it may include the actual 8 layer PCB assembly (copper + fibreglass + ... ).
If so, don't do it!
While PCB construction is a notionally straight forward enough task it requires many processes, each requuring substatial experience and a degree of arcane knowledge to get right consistently.
If you are including the etching and through hole plating requirement you'd have to be utterly awesome to even consider it - and even then it should be avoided if at all possible. The cost of building a fabrication plant for the actual PCB is liable to be better spent elsewhere.

PCBA assembly is another matter. Doing it yourself can lead to sorrow but is eminently doable with enough competence and attention to detail.

BGA assembly is traditionally said to be difficult and not readily achieved without skill and experience BUT I have also seen reports by people who are competent in PCB assembly who have extended this capability to BGA assembly with no more effort than they had expected. So, if you are mechanically competent and have people skilled in PCB assembly at lesser levels BGA may not be the disaster that quite a few people report it to be. [Hopefully that manages the right mix of encouragement and warning:-) ]. [Note: I have never attempted BGA assembly personally and would try to get it done by those with competence and experience where possible. I'd anticipate being able to do it acceptably if theere was no choice.]

For lab scale prototype production a pick and place machine is not an essential and the cost is high enough that the money could usefully be spent elsewhere. I have seen production lines [in China] where an automated pick and place machine was run alongside a "manual pick and place machine" consisting of about 20 women at a long table with component bins and tweezers. Some jobs were apparently more cost effective on a manual machine. A skilled assembler can get extremely proficient at placement of SMD parts and offers a high level of flexibility for prototype manufacturing.

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  • \$\begingroup\$ An edit was time barred. The lab would be used by an educational institution as well for training of students. Students can use simpler equipment. Is a benefit in buying something more advanced? \$\endgroup\$ – partoa Jul 25 '12 at 4:04
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    \$\begingroup\$ @partoa - what country? Iran? Making a multi layer PCB is an immensely challenging undertaking. It is certainly within the ability of an educational institution to do it if it was decided it was relevant to the course, but it is a non trivial task and somewhat peripheral to actual electronics. Optical lithography, etching, plating, drilling, laminating presses, prepreg stock materials, ... . A course in its own right. \$\endgroup\$ – Russell McMahon Jul 25 '12 at 7:39

protected by Dave Tweed Nov 12 '14 at 16:21

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