MicroZED

Den søndag den 20. oktober 2013 22.26.43 UTC+2 skrev snipped-for-privacy@gmail.com :

.com:

Linux, if

eed at least

ual peripherals implemented how many fpga resources are left?

modes.

LTIPLE, DIVIDE, STR/BLK, etc. as well as instruction cache and pipeline. T he resources are better used for I/Os.

so you have an engine, all that is needed is a gastank, a gearbox, four wheels, some seats, and a chassis and we can drive some where

-Lasse

No, what the product will sell for is largely irrelevant (only to the point that cost + desired profit > price). The only metric that matters is what does the alternative cost. Whether it has a higher performance is likewise irrelevant. If there is no cheaper way to do it, fine (as long as it meets cost + profit > price).

You'd better take that cost into account before you spend the money on development.

Everything is debatable (except Obamacare within the government) but it is enforceable. They'll get you on the software license. As long as you can program it without using any of their software IP (either directly or indirectly), fine. You could probably sell them as doorstops without worry. ;-)

Of course Avnet is showing zero stock...

Cheers

Phil Hobbs

Den lørdag den 19. oktober 2013 19.52.25 UTC+2 skrev John Larkin:

I just stumbled over this:

it's more expensive and it doesn't have any connectors, though that might be an advantage if you make a carrier board and want to put it in a box

looks like on of the guys behind it hangs out in comp.arch.fpga and they se em to offer 10+ years life time

-Lasse

That's by far not the only thing that concerns me.

OK, well, someday, I'm sure, I will be led kicking and screaming down that path. The lack of ability to examine the solder balls worries me. I do all my own assembly using an aging P&P machine and a modified toaster oven.

Jon

In all the places I've worked, we had the least trouble with BGAs. At the PPoE the big problems were QFNs that didn't wet on the sides. BGAs never had a problem, until they have to be replaced. That never goes well locally. It's something that one has to do constantly to get right. We send it all out at the CPoE.

The great thing about inspecting all those BGA balls is that you can't inspect them.

Actually, there are some optical gadgets that let you peek under the chip, from the side, and see the first 3 or 4 rows of balls fairly well. And you can see through the entire array, for debris and such. We just bought a good one for around $30K.

People do BGAs at home, too.

These are cool:

We use them for rework, but they would be good for hand assembly, too.

I have overcome my fears of 1206s, 0805s, 0603s, SC70s and US8 packages (almost), TSSOPs, and BGAs. SC79s and 0402s still terrify me.

We rework BGAs in-house. We had one bunch of products that kept getting expanded functionally so we had to pull the 780-ball FPGAs and put in compatible ones with twice the CLBs. We did about 20 boards, no problems.

BGAs are great. Much more reliable than fine-pitch leaded parts.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

And that's exactly the problem. They don't fail initially. But they can later, on boards that are subject to lots of mechanical or thermal stress. The thermal stress is often delivered by the BGA part itself. There is a whole little industry that sprung up when BGAs were introduced. People learned re-balling and other things and then repaired game consoles, expensive laptops and such.

Smart choice. I am also a believer in sending stuff to the pros unless you have real pros in-house. Trying to kludge it with BGAs just isn't worth it. But I don't use BGA, I prefer parts with leads that can take some stress. Leadless is ok if the part is very small, like the little DFN.

They say we can have a couple in here this week.

Does anyone know if it is possible to get away without solder paste, for prototyping purposes? Or do something like tin all the pads first, place, apply hot air?

Very nice, but not at all that micro: 10cmx5cm... :-/

Best regards, Piotr

I've never had anything to do with BGA's but I thought you could re-flow if you had a suspect joint but replacement of the package after removal required re-balling.

Thanks, I am talking about the initial soldering operation on a bare board. AFAICS I could just plonk the BGA down on its pads, without solder paste, with some flux. Heat everything up and the balls should melt and the package self-center.

The point would be to avoid the initial stencil fee and full-up setup charges - and delays - when you just want to make a prototype unit.

you can get stencils that have the usual BGA sizes

and many of the cheap chinese PCB prototype places now offer a stencil for something like 20$

-Lasse

That's why inspection is usually not done :-(

Can it reliably detect flux residue somewhere in the middle? It's hard to clean under a large BGA and then a few years down the road something might quit working.

How do you get the flux back out? Do you use Kester 951 flux?

Those are boulders. Some time around March next year I'll have to deal with 01005. Not looking forward to that but as John Wayne said, man's gotta do what man's gotta do.

As I get older and SMT becomes smaller I have found that even the Donegan 5x visor is sometimes not enough.

Big BGAs need underfill to reduce the stress on the balls.

Cheers

Phil Hobbs

Hi Lasse,

Yes I saw those that JL posted. Still an extra cost, and need to make sure I have in stock, and need to use solder paste which always goes off by the time I need it etc. Although certainly it is an option especially if I get my assembly house to do it (using their paste).

But, is paste really essential for the process to work? Aren't the solder balls already made out of - well - solder?