Re: Designing for and soldering a tiny BGA

On Apr 11, 4:33 pm, linnix <m...@xxxxxxxxxxxxxxxxxx> wrote:
On Apr 11, 1:17 pm, zwsdot...@xxxxxxxxx wrote:

On Apr 11, 3:20 pm, linnix <m...@xxxxxxxxxxxxxxxxxx> wrote:

difficult and IMHO very ill-advised to attempt fanout of a dense-pitch
MBGA without at least four layers. I know it's possible to do it in 2,
but it's not ideal.

If you need most of the pads, 2 is impossible.

Not quite impossible, just a very bad idea. I have seen commercial
products where they put a via off-center inside the pad and use mask-
defined pads to keep the paste JUST off the via's hole, then using
very fine space/trace rules you can get two signals out between every
pair of pads. Very nasty.

Perhaps for larger pitch. But for 0.5mm pitch, you need 0.1mm to
0.2mm lines. I would rather wire-bond (0.1mm wires) than using such
nasty PCBs. One possiblity is to wire-bond a jumper block opposite
the BGA, to flip the pads inside out. By the way, I just got a quote
for bonding wires at $0.001 each. So, for higher volume, wire bonding
is the way to go.

I think this debate shows the difficulty of designing a PWB for fine
pitch BGAs. It should only be attempted after a great deal of
research in how not to make coasters.

As to the comments by zwsdot about Eagle vs. FreePCB, if I am not
mistaken, his comments show that he has not used FreePCB. If you take
a look at the package, I think you will find very few shortcomings vs.
Eagle or other available packages. My main point was actually about
Eagle. It has some very significant disadvantages as zwsdot mentioned
in addition to the point I was making about the licensing. Although
at one time Eagle was the package of choice for hobbyists, I think
that time has passed and there are any number of PWB layout packages
that will do a very good job without all the drama of Eagle.

Rick
.

Relevant Pages

  • Re: Creating a device in Eagle
    ... >so I thought I'd build a device, symbol and package for it. ... I don't use Eagle, so I can't help with your first questions. ... footprint or group of pads for it to connect to. ...
    (sci.electronics.cad)
  • Re: Designing for and soldering a tiny BGA
    ... If you need most of the pads, ... As to the comments by zwsdot about Eagle vs. FreePCB, ... a look at the package, I think you will find very few shortcomings vs. ... Eagle or other available packages. ...
    (comp.arch.embedded)
  • Re: Silicon Blue last datesheet correct URL
    ... parts have 5 volt compatible I/Os on three of the four banks. ... they flag compatible pinouts using the same package. ... traces between the pads or even vias within the pads. ... want to plate 10 mil holes. ...
    (comp.arch.fpga)
  • Re: Designing for and soldering a tiny BGA
    ... If you need most of the pads, ... Eagle or other available packages. ... able to "do it yourself", then yes, assembly houses are not cheap. ... But one that can do BGAs is no more expensive than others. ...
    (comp.arch.embedded)
  • Re: Designing for and soldering a tiny BGA
    ... If you need most of the pads, ... Eagle or other available packages. ... able to "do it yourself", then yes, assembly houses are not cheap. ... But one that can do BGAs is no more expensive than others. ...
    (comp.arch.embedded)
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