Designing for and soldering a tiny BGA

he

I would strongly suggest that you not use eagle and instead use FreePCB. Eagle is not really freeware and you can get into problems when parts are moved between paid and unpaid systems. It also has an antique interface.

Go to freepcb.com and check out the forums there. There are several users who are very happy to offer excellent support and I expect someone will even provide a footprint if you tell them the exact part number of the chip you are using.

You might try Olimex in Europe for board fab. They have some limits on the pitch they will produce and so they may not be suitable for a

0.5 mm pitch BGA. Designing for a part this small will take some detailed knowledge of board design and you will want a lot of hand holding.

Then the fun begins when you try to solder the parts!!!

Rick

the

K?

I would just write a simple program to generate the pad layout. BGAs are easy to build PCB, but difficult to mount the chip.

I am pretty sure they can't do it. The dog-bones holes would be too large for their minium drills You usually need laser drill for such. I would look to your west, my east for such board.

Absolutely. Does the OP have X-ray machine?

Nothing is truly free. EAGLE is a mature commercial package with good peer and vendor support (even for the free edition). Ceteris paribus, it is a much better choice than FreePCB for this reason alone. And of course there is no problem creating a footprint for a BGA - simply set the grid size to the pad spacing, click the left mousebutton 81 times, and you're done. It's a matter of a few minutes to draw the footprint for a 9x9 device. If you look in Cadsoft's download areas you'll probably find some BGA libraries I drew up (StrongARM devices, I think

- it's been a long time).

However the point is moot; the free edition of EAGLE is limited to two signal layers and that really isn't enough for this application. It is 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. With filled-vias (center of BGA pads) and/or blinds, 4 would be possible. Otherwise, I would suggest 6 to 8.

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.

h ,

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

Define cheap!

Most PCB etch shops have online calculators to give an idea of costs.

Size, layers, number of solder resist and layers affect the cost. So do it in minimum layers I would suspect 4 for BGA, one side ident and sodler resist different on two sides.

0.5mm pitch and smaller is possible easily in Eagle. DOne boards with smaller pitch (0.4 and 0.35 mm pitch from memory).

Sort out what your min track/pad width and clearances are with each PCB etch shop you find. To see if they can make your

As others have said the paid for version is more likely to support the number of layers you need

Have you checked the Libraries section of the downloads available on

(eagle website) I am sure some BGA are there.

Create a group of 9 on correct pitch, copy and paste group of 9 make sure on corect pitch.

I hope you have somebody who has Xray and other facilities for good board population.

Plenty of PCB etch shops in UK, look at project pooling as a way of reducing costs.

(also do stencils for solder paste process) Quick circuits

Newbury Electronics I have always found expensive

Many others do a search on your favourite search engine/phone book trade directory/electronics magazine.

A good board stuffer/populater will know of some PCB etch shops.

--
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AFAIK FreePCB does not contain a schematic editor. It is very nice to have that and the layout integrated. Personally I am using Eagle and found it rather nice. But Eagle has one serious shortcoming: No hierarchy. That's why I am looking for something better but haven't found anything better yet. Tried gschem, KiCad and some others but they all have an issue or more.

Ian: If you are on a tight budget also for production try to avoid BGA like the plague. Only sophisticated and professional (as in expensive) assembly houses can handle those. This is not the stuff to try in a modified toaster oven.

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rickman wrote:

Yup. As Lewin mentioned, the crippleware version of EAGLE is a poor choice for this kind of density anyway.

As several have mentioned, BGAs are also a questionable choice for hobbyists or those otherwise without X-ray inspection equipment.

I suggest the OP become familiar with this (broad) concept:

EAGLE *is* freeware; it is NOT Free Software.

and you can get into problems

Yup. Cadsoft EAGLE: Now with new improved DRM that can lock up your work product in their proprietary format.

Being paid-up does NOT grant immunity from "The EAGLE Virus".

**The Downside of EAGLE** by Markus Zingg *-*-website+reuse+paying.*+*-I-will-switch+c=racked-*+*.would.not.help.*+zzz+after-*-*-version-*+copied+*.*.unlock.*.des=igns+*-*-*-*-exchange-*-*-*-*-third-party+reused+qq+*-*-single-bit-*-*-*-*+=useless+*-*-*-projects-could-no-longer-be-opened

Yup--but even a chimp can use well it within a few hours.

It would be good if those folks advocating that LAYOUT editor would mention that it needs a SCHEMATIC CAPTURE app

--perhaps mentioning some candidates for that.

Free Software apps (including Rick's suggestion) are available for this task. Eschew those that are just "freeware".

DJ has occasionally gone off the deep end in demonstrating how UNlimited Open Source software is:

*-*-square+zz-zz+qq+= boards-up-to

NOTE: gEDA is *not* a native Windoze app; if you are running that platform, you will have to compile the app yourself.

*-*+depending.upon.your+Windows+org+org+gEDA-i=s-free-*-*-*+your-*-*-expertise+theoretically.possible+org+version+*-*-your=self+distribution.and+org+missing.dependencies+*-*.*-despair+Linux

Hi again,

As I mentioned - board population is taken care of.

The chip in question has all the signal stuff in pretty much the last 2 rows of pins around two edges. nearly all the other pins are ground.

I'm tempted to get a tiny soldering iron bit and try to solder some miniscule wires to the chip... but that wont do for the final product...

Then 2 layers should be fine, but still need small holes to route the inner row.

Tee hee... Here is the 'OP's (Ie. my) website:

Judge for yourself if I've heard of the GPL ;-)

Im using eagle because someone who actually makes boards for a living recommennded it. Im not likely to be making many, or complex, boards, and right now, just want to draw something, get it printed onto a board and have someone else stick the chip onto it. Im not up for a free software debate, and i think my position on the GPL is probably obvious from my website ;-)

If I end up with the time to play I might look at other stuff. For now, Eagle works (even though I dont really know how to use it yet). I dont think I'm going to worry about 'lock-in' for a

volucris wrote:

I guess so.

Sounds like he recommended the 16-layer version.

An 80-pin BGA sounds plenty complex to me

--especially on 2 just layers.

Cadsoft's non-intuitive DOS-era interface has been mentioned. I'm thinking that as long as you're starting from zero, a modern (Free Software) app might avoid that frustration from the start.

Interesting combination of statements.

Well, you ARE asking for a pre-built footprint.

**Using someone else's components** is *exactly* the kind of thing that triggers The EAGLE Virus: Once you close the app, you can't open your file again.

Now you have to research how to crack the app. (Actually, it would be better to have those instructions in-hand

*before* using software known to be DRM-infested.)

...or even better than that, eschew DRM and crippleware and go straight to an **unencumbered** Free Software app

(as long as you're at zero on the learning curve anyway).

If that is important to you, then Eagle it is. I have not found a strong need for that. I would like to have simultaneous integrated schematic for back annotation, to be able to do it on the fly rather than batch mode. I brought this up once and did not find anyone who thought this was a good idea. They seem to feel it is better to have the two separate so that you can use whatever combination of tools that you prefer.

There are also other tools that support combined schematic and layout. I have not tried them because they are primarily Unix/Linux based and support for Windows is minimal. One fine day I will get a Linux machine up and running and give some of this a try. But in the mean time, FreePCB is an excellent tool and I much prefer it to Eagle with its bizarre interface and licensing issues.

If, by expensive, you mean that they charge for their time vs being able to "do it yourself", then yes, assembly houses are not cheap. But one that can do BGAs is no more expensive than others. In fact, my last board was designed with all leaded devices for ease of debugging and assembly. I picked the low cost assembly house and it turns out they also do BGAs. So my next job may well use non-leaded parts, either QFN or BGA.

Rick

concept:

Software.http://google.com/search?q=cache:vYwHVQAGkr8J:en.wikipedia.org/wiki/O...

Zingg

THAT is my main objection to using Eagle. I understand their need to enforce copyright, but they are going way overboard.

I don't agree. I learned it once in spite of its arcane and non- intuitive interface. I came back to the project six months later and I found I had to learn it all over again; it is just sooooo... different from any other program I use every day.

Or maybe I'm just not your typical "chimp" ;^)

I never expect that needs mentioning. Schematic capture and layout are two independent steps. They are linked by the netlist. It is nice if they share a common data base, but not really essential. Many users of FreePCB also use Tinycad for schematic capture, but it really doesn't matter. Personally, I don't care for Tinycad.

Rick

d

I am not trying to push you to do something you don't want to, but I'll give you some more info. People often recommend what they are familiar with even if they don't know the other choices. I expect the licensing is not a real issue for you, but I think you might find the user interface to be a PITA. FreePCB is a much easier to use tool which should be important to a new user.

I guess that is what I am trying to say. If you are going to learn a tool, why learn to use a poor one?

Rick

he

I've had very good service at a reasonable price from ASK:

They will require a stencil at about =A3250 if they get it made, but they may be able to use one you supply which could be cheaper.

Leon

I'm flabbergasted. How can anyone live without integrated schematic and PCB?? This is amazing stuff, to hear that people would voluntarily choose NOT to have integrated schematic capture and PCB layout. Two sets of libraries for every part? FULLY MANUAL checking of schematic vs PCB??? Hell, if that is the way people prefer to work then give me Bishop Graphics. Having those two features integrated saves me dozens if not hundreds of man-hours a year.