Dead bug soldering a 256-pin BGA?

[themacman33]

I found an Altera Cyclone II in a 256-pin FineLine BGA package (1mm pitch)
Unfortunately, the pins were broken out into an internal layer, so I heat gunned it and looked for a breakout online.
Since it is a proprietary package, there aren't any prototyping breakout boards available. I could make my own board, but with such small traces and visas, it's not cost-practical to buy or make a small batch of PCBs. My only option is to dead bug it.

I've dead bugged 14 pin packages before, but nothing this huge and dense.
Is this doable? Any tips? Are there any other options I have?

You may think that it's crazy to do all this for a $27 part, but I'm a high-school student who doesn't have any reliable income. If successful, I will use it to make a prototyping system, or a logic analyser.

Thanks, Mac

[zapta]

Why not just try it? Worst case you will improve your soldering skills.

[jahonen]

Our lab guy did it:



Note that above thing has just 144 balls, and I what I heard from him it was quite a job so 256 ball BGA might be too tedious. But it worked just fine.

Regards,
Janne

[AndyC_772]

Don't do all the wires individually. A lot of the pins on a device like this are power and ground, and you'll save yourself some work as well as improving the chances that the finished job works if you figure out which these are and join them together locally at the device.

IIRC many of these FPGAs have a square of ground pins in the middle, so join these all together in a grid at the device. Outside is a ring of power pins, so these can all join together too. Fit decoupling caps between power and ground locally at the device as well.

You also only need to solder to the configuration pins plus the ones you'll actually be using for I/O. Any unused pins can be left floating - but try and make sure these are pins which will remain accessible, as no pin ever remains unused forever in prototyping.

[themacman33]

Ok, thanks. I'll probably etch my own pcb to solder the deadbug wires to, making a sorta prototyping layout. Is a sharp soldering iron tip recommended?
I'm thinking of just using 30AWG Kynar wire-wrap wire. This should work, right?

Thanks,
Mac

[IanB]

I haven't done it, but I think you are going to want to use the finest wire you can manage, pre-tin the wire ends, use plenty of flux, use a conical tip iron, and just dab the end of each wire onto the solder ball with a touch of the iron.

Make sure you plan out your order of soldering so you don't block your access for attaching later wires with wires soldered previously.

[Prime73]

if that one is not a fake... I don't even know how this is possible.

[marshallh]

Somehwere on the net there is a japanese fellow that deadbugged a 484pin cyclone to use it for mandelbrots...

But really, with Oshpark 4layer there is no excuse. 256pin is not that big. The pcb might cost $20.

[themacman33]

Wilfred: Yeah, that makes sense. I'm also partly doing it just for practise, and to say I have. I figure I'll sink $10 into it for wire and my own PCB, and that's it.

Marshallh: I've checked out OSHpark, and they have 6mil min. spacing and trace width, which is too big, and 13mil minimum drill size, all of which is too big for such a high density BGA part.

Thanks for replying.
-Mac

[marshallh]

Such specs are perfectly fine for 1.00mm BGA, I've done many boards. If you push the specs a bit you can get 0.8mm somewhat

Heres one

[poorchava]

Even if you get all the connections ok, some stuff may not work. I had a friend in uni who deadbugged some ARM9 from atmel (150-200pin BGA). It generally worked but for example PLL wouldn't lock - too long wires and weak grounding.

[nctnico]

Ok, thanks. I'll probably etch my own pcb to solder the deadbug wires to, making a sorta prototyping layout. Is a sharp soldering iron tip recommended?
I'm thinking of just using 30AWG Kynar wire-wrap wire. This should work, right?

I would use thin enamel wire (the stuff used to wind transformers). You can melt the insulation off with your soldering iron. You can buy enamel wire in different colors which helps a lot to seperate power and signal wires.

[free_electron]

Ok, thanks. I'll probably etch my own pcb to solder the deadbug wires to, making a sorta prototyping layout. Is a sharp soldering iron tip recommended?
I'm thinking of just using 30AWG Kynar wire-wrap wire. This should work, right?

I would use thin enamel wire (the stuff used to wind transformers). You can melt the insulation off with your soldering iron. You can buy enamel wire in different colors which helps a lot to seperate power and signal wires.

and die of lung cancer ten years later. that stuff is VERY toxic when burnt off.

[JonnyBoats]

I say go for it! If you get something working think how great the project will look on a college or job application 

Who wouldn't want to hire someone who had hand soldered a 256 pin BGA, debugged it and ended up with something that works?

[themacman33]

Alright! I'm about to start. I'll be documenting it on my blog:
www.digitalpineapple.blogspot.com

[skyline_stu]

Been there, done this too many times to count.
Here are my suggestions.

1. Use either the wirewrap or enameled wire. The enameled wire will be easier to solder to and less likely to break where you have stripped off the insulation. Yeah, watch the fumes (toluene di-isocyanate fumes can sensitize you)
2. Pre-cut your wires to a suitable length to allow you to have the pcb flat and the device at 90' to the board.
3. Solder the wires to your IC's first row, standing straight up. When a row is done, bend each wire through 90' and solder these to your BOB* pcb. Use fine tweezers and a fine pick to comb the wires semi straight.
4. Repeat many times, you will find that this is how the picture from Prime was completed.
5. You will find that the enamelled wire is surprisingly flexible, until you have a lot of wires attached.

*break out board

Take your time and all will be OK. I do this on a semi regular basis and have always had excellent results.
Don't forget to use plenty of flux and clean it thoroughly afterwards with flux remover spray. Just be sure that the cleaner won't attack your wire !!!
After testing, epoxy encapsulate the works. 5 minute Araldite works well. Hot melt glue just doesn't cut it.

Be aware that there may be signal integrity issues at high speed..

FYI, 20 odd years ago I needed a way to convert a 84pin PLCC into a PLCC plug. I used a dremel with a diamond burr to grind away the encapsulation down to the lead in wires, removed the silicon die/bond wires and soldered pin by pin from the chip to break out board. Afterwards, I bound the flying lead wires together and epoxy encapsulated the lot. It worked 1st time (and probably is STILL to this day)

OSHpark design rules for the 4 layer boards are 5/5mil trace/space and drill holes to 0.011". 
You should be able to make the board well within those rules.
It's not readily apparent on the web site.  I've yet to find another manufacturer to match price and quality.

I've had them make me boards that adapt 80 pin QFP (0.4mm) to 84pin PLCC, rotated through 90'. 
A pain to solder in, but nothing is available for this application. 

[Artlav]

if that one is not a fake... I don't even know how this is possible.

Not fake.
It's from a collection of an electronics repair store, displayed as a warning for all who want to fix stuff themselves (but don't have a clue).
Here is the rest of it: http://zremcom.ru/article/interesting/36-samremont

I.e.:
3. Super-glue a cracked chip down.
4. Vented capacitors? Just tape them shut!