SparkFun Forums

[baluba]

Wouldn't it be great with one of these to mess with the new AVR32 uC, which is 256BGA, 1mm pitch.

http://electronicproducts.com/ShowPage. ... n2006.html

Perhaps SFE can try to reengineer one of these, unless they are patented of course....

I tried to find out more how it works, but there is no information yet on their site, and the board is not yet available. Must be some holes beneath or something...

erik

[leon_heller]

Each solder ball connects to a pad, which is connected to a small via. A multilayer PCB is required, so that all the connections can be brought out.

Reflow soldering can be done at home, but one can't be sure that all the connections have been made properly. Assembly houses use an X-ray machine. A company I've used for prototype assembly can mount them quite cheaply, including X-ray - 50 GBP (their minimum order) for a small number of boards.

Leon

[beebop]

Hey, Baluba,
http://www.schmartboard.com/index.asp?page=movie
tells about how it works: thick solder mask, solder in the groves. It's for hand soldering, prototyping.
Some of their other products looked good too.
Thanks for pointing it out.
Regards,
Robert

[baluba]

Yeah, I tought I misunderstood something when the other guy was talking about wave soldering, but not so.
I got an email from the company explaining the product, they haven't released it yet:

The BGA balls will easily be placed on the pads on the SchmartBoard, as the balls will actaully go into "holes" on the SchmartBoard. You will then tape the BGA down and turn the SchmartBoard over. The back of the SchmartBoard will have "pass-through vias" for each ball. You will use a soldering iron to either touch each via(for each pad) or have the option of using solder and melting solder over the back of the board. We are still in final testing and hope to release boards in late May.

[FESCSteve]

Use solder mask defined pads with thick soldermask. Design the PWB with vias in the pads - leave the vias untented on the opposite board and you can hand solder the BGA devices.

Steve

[Philba]

Use solder mask defined pads with thick soldermask. Design the PWB with vias in the pads - leave the vias untented on the opposite board and you can hand solder the BGA devices.

Steve

very interesting idea. what size vias? I assume I could make a library part with through hole pads where the balls are and solder from the other side.

why untented? I thought tenting prevented the plating in the hole from being etched. did you mean no annular ring? can you explain that issue?

Phil

[FESCSteve]

I should have prefaced my comment by saying that I've never assembled BGA devices in this manner so take that into consideration. I'm just throwing ideas out there for thos who may need to design with a BGA device and can't reflow solder.

Re - tinted vias: I guess I should have said 'no plugged vias'. As long as you leave the opposite side clear of soldermask so that you get good heat transfer you should be able to reflow.

The problem with this idea is that you will really need to add some solder through the via. If the part or pads are not absolutely co-planar, then you could have a case where one ball will not solder to the pad when it's via is heated from the opposite side. Even adding solder at that point may not help.

I would only attempt this with low ball count, course pitch bga devices though.

Steve

[Philba]

well, even if you haven't done it, it does sound like a workable plan. I don't know if I'll do it but it seems like the via approach combined with either hot-plate or hot-air reflow might just work.

Reflow on a hot plate, flip the board over and touch up the vias with an iron. Maybe instead of vias use plated through holes of the right size with very small annular rings. figuring out the size may be a trial and error thing.

alternatively, maybe i should build that home xray machine...

[FESCSteve]

When I say vias, I do mean plated though holes with small pads opposite the BGA.

If you have a means for hot air reflow, that would negate the need to use an iron and the plated vias. We reflow BGA's all day in a convection oven and rework them with hot air.

Steve