Hi, i’m developing a project around the NGW100 reference design(uses Atmel AVR32 AT32AP7000 SoC) and want to start creating the first prototypes of the product, i’ve never worked with this kind of package, and i assume that it cannot be soldered by hand. What options exists for this? BatchPCB can handle this task? Can anyone point me some suggestions?
Thanks in advance!
Do you have the Gerber files? Or do you need to design a PCB for it?
Assembling BGAs at home can be done, but it isn’t easy. You really need a company that can do it for you and check the connections using x-ray or optical equipment.
Leon
With practice, you can solder many BGAs by hand using an indirect heat source (hot air, etc). The problem is aligning the package, and checking the connections. You will likely have many failures though.
I used a hot plate to solder a BGA with a couple hundred balls. Took a couple tries to find the exact right amount of solder paste to use - but once I figured that out it was fine. Alignment isn’t too bad - but one important suggestion - when making your footprint for it - put corner markings in the top copper layer - not the silkscreen. Silkscreen registration can often be off by 5 mils or more - so you definitely don’t want to try to align your part to it!
I was placing dabs of solder paste with an air powered solder paste dispenser that allowed me to make very accurately sized dabs of solder (and yes - I had to individually place each drop of paste!). A solder stencil would probably be just as effective if not more so.
There are a couple commercial products out there for soldering BGAs. Schmartboard makes some BGA carriers that I have no experience with. Another company makes a sort of plastic film that you put over your footprint on your own PCB - I have a sample at work of it that I’ve been meaning to try out.
Can't help the OP with BGA issues (I haven't encounteredNleahciM:
I was placing dabs of solder paste with an air powered solder paste dispenser that allowed me to make very accurately sized dabs of solder (and yes - I had to individually place each drop of paste!). A solder stencil would probably be just as effective if not more so.
one in a hobby capacity).
Is it really necessary to “dot” each pad without spilling to
other pads?
Some of the fine pitch footprints I’ve seen and used appear
to have a single apeture for a row of pads. The solder mask
“fingers” present between pads are at or beyond the limits
of the PCB fab process.
I have placed a ‘stringer’ of solder paste by hand form a
syringe along this apeture and found soldering to be very
easy. I marvel at the paste becoming molten metal and
linking itself to the pad centres. In many cases slight
misalignment of the body is automatically corrected as the
part tried to “float” to the top of the molten solder puddle.
Wouldn’t a single apeture stencil for the entire BGA array
work just as well?
I don’t have any problems soldering fine pitch devices without solder mask, using drag-soldering. BGAs are another matter, prototype assembly houses insist on using stencils for them, I’ve found.
Leon
bigglez:
Can't help the OP with BGA issues (I haven't encounteredNleahciM:
I was placing dabs of solder paste with an air powered solder paste dispenser that allowed me to make very accurately sized dabs of solder (and yes - I had to individually place each drop of paste!). A solder stencil would probably be just as effective if not more so.one in a hobby capacity).
Is it really necessary to “dot” each pad without spilling to
other pads?
Some of the fine pitch footprints I’ve seen and used appear
to have a single apeture for a row of pads. The solder mask
“fingers” present between pads are at or beyond the limits
of the PCB fab process.
I have placed a ‘stringer’ of solder paste by hand form a
syringe along this apeture and found soldering to be very
easy. I marvel at the paste becoming molten metal and
linking itself to the pad centres. In many cases slight
misalignment of the body is automatically corrected as the
part tried to “float” to the top of the molten solder puddle.
Wouldn’t a single apeture stencil for the entire BGA array
work just as well?
Long answer shortened: it could work, but probably wouldn’t.
Remember that the spacing of balls can be fairly large - I know some BGAs are 50 mil pitch and there are probably some of even coarser pitch. In cases like that if you just smeared across the entire area beneath the BGA, you would get balls of solder forming between the pads. Balls of solder could lead to shorts and various other problems.
With a finer pitch part I’d think the problem would still exist but be less pronounced. Plus, with my experiments with soldering BGAs - I found the process to be fairly sensitive to using just the right amount of solder.
So the films that I mentioned earlier should take care of the solder paste application problem for most people. You can see more about the process here: http://solder.net/stencilquik/default.asp
With those, you just need to find a decent way to heat up the board evenly.
Thanks for your help. That stencil method pointed by NleahciM looks very promising. Can you point me a good PCB+PCBA service for a short run?
I get very good service from these people:
http://www.asktechnology.co.uk/
Their prices are very reasonable. They might not be much use to you in Chile, though.
Leon
The stencil method looks very plausible. What about this:
http://www.instructables.com/id/Making- … e-at-home/
Looks like can get a stencil for solder pasting the entire PCB. And a very low cost, what do you guys think about this homebrew method? Will the acid don’t eat the space between leads with too much pitch?
I’m thinking to give it a try.
rcarvajal:
The stencil method looks very plausible. What about this:http://www.instructables.com/id/Making- … e-at-home/
Looks like can get a stencil for solder pasting the entire PCB. And a very low cost, what do you guys think about this homebrew method? Will the acid don’t eat the space between leads with too much pitch?
I’m thinking to give it a try.
Looks like clever way to get a stencil. He uses the mask (or keep out?) to make his artwork which is a little too big. There is a better way in eagle. Make a copy of the project, ripup the routed traces on the board, deselect everything but the layer you care about (top for example) and you will see just the smd pads. A negative of that can be used for the stencil.
The issue I see with using copper is that you have to be very careful with it. It has to be 100% flat. Another issue is aligning your stencil. Since the copper is opaque, you will need to be very careful when aligning it.
The etchant will cause some expansion of the open areas of the stencil (called undercutting) but it will basically be the thickness of the copper sheet. It shouldn’t be a big issue.
I have finished a few projects at work with this chip. The prototyping cost can be quite high.
I have made a few boards using ~ 6-layers using 80% of the AP7000 pins. You need to use 5mil tech and spacing in order to fan out the ap7000. You can get away with 6 mill, but might need to add a second layer.
The pads I use are dogboned, with tented via’s just in case. My board house will place a BGA for me for ~ $75 with xrays photos. I haven’t had any bad ones come out yet. They use IR with a standard heat profile to place the chip
To start, its best to use the STK1000, because all of that hardware is proven out, and will help you generate the code, and get some time using the new studio and compiler.
Sample cost…
6 layer PCB (5mil tech all around) 12 pcs @ $131 each
Components One boards ~= $178
PCB Attachment done out of house $75
=$384.
This does not include my engineering NRE for the orcad work done, and time and testing.
It’s looks like a expensive task then.
Looks like this is not trivial anyway… maybe the best choice is to switch to another microcontroller with a more easy to work package, i’m looking towards the AT32AP7001 which is on a 208 QFP package and have nearly the same specs of the big brother.
Thanks for the feedback.