BGA pads with Vias

Via eyeballs

No. This isn't a closeup of an owl face.

There is still some debate on how best to create a land pattern for a 0.4mm pitch BGA. We recommend soldermask defined pads at that pitch. But that's not really what this post is about. Although this land pattern uses non-soldermask defined pads which can encourage bridges. If you need to cross a river, encouraging bridges is good. If you're trying to make a board work, they are not.

In the case of the two BGA pads shown, I really doubt you would have to worry about bridging. That's because the solder ball would most likely be sucked off the BGA due to the capillary action of the via in the middle of the pad. You most likely wouldn't get bridging. You most likely wouldn't get any contact of any kind at all. This will not work.

Duane Benson
Hoot. Hoot.

Speaking of Small Packages...

T'was a a dark and stormy night when the news came through. Joe Layout had been both dreading and preparing for years. But it had always been little more than rhumors from a far off land. It was a looming threat, always dancing in the distance, but never quite real.

Until now. 1.27mm, 1.0mm, 0.8mm, 0.5mm, 0.4mm... and now... drum roll please 0.3mm pitch. I just got Shrinking BGA pitchan email announcing an Amkor 8 x 8mm 368 ball BGA at 0.3mm pitch. Yikes.

There's still some controversy over the best way to make a 0.4mm pitch BGA land pattern. Some say says you need to use solder mask defined pads. Some say you still need to use the non-solder mask defined pads. Now we throw something 25% smaller into the mix.

The image isn't to exact actual scale - because I don't know how big your monitor is - but the parts are in relative scale from 1.27 pitch to 0.3 pitch.

Duane Benson
If you can't see it, you shouldn't eat it

Open Source. What is it Good For?

I've written about open source hardware (OSHW) a few times before. Like this and this. I've understood open source software for quite some time and over the last few years have been starting to get what open source hardware is all about. It is different than open source software.

With software, your tangible product is essentially intangible. Your acquisition and distribution of an open source project can be virtually free. Not so with hardware. Someone has to physically build something, which costs time and money in parts and labor. Really though, all that means is the proliferation of an open source hardware product just takes a little longer. If you look at it as the design being open source more than the actual product, then it gets to be more and more similar to software.

While open source software has moved into real business, hardware is still more closely associated with the hobbyist community. That is changing though. Ti's Beagleboard is serious stuff from a serious company. Some of the hobbyist catering OSHW companies are growing to or have grown to the point of being serious businesses (Adafruit, Sparkfun).

This all begs the question: "What is open source hardware good for?" Let's divide and conquer. Or, at least, divide and explain.

  • What does it do for innovation?

History is rife with stories of great inventions that were not commercially successful because the inventor was a good inventor but was a lousy business person, didn't have access to funding or just didn't have the drive to build, promote and sell the product.

With OSHW, companies that do have the drive, funding and know-how can pick up an open source project from a developer that doesn't.  There are none of the IP concerns that sometimes keep big companies from taking on product from independent inventors. Great products that otherwise would stay hidden can make it out in the world.

Some OSHW companies, like Adafruit compensate the designers who's product they sell. No marketing or selling expense for the designer and yet money comes in to them. Much reduced design expense for the seller, yet they can build a business.

  • What does it do for small companies?

It's another way to jump-start design or production of products that will fund the small business. It can reduce the barriers to entry. People who are good at designing but not so good at selling can still earn money. People who are not so good at designing but good at selling can earn a living. People who are good at both designing and selling - they have the best of both worlds and can earn a living. Products that would otherwise stay in obscurity can more easily make it to the world.

  • What can it do for big companies?

The answer to this question has been the longest in coming, but there are more and more answers showing up. Take the Beagleboard from Texas Instruments. It got a new processor (the OMAP) out into the hands of their customers quickly. It was a great promotional tool. The software side of an organization could get started with the processor without having to wait for the hardware folks to design, layout and build the hardware. The hardware folks could see how the part and its accessories work in real life.

OMAP users could get a jump-start on complex tasks like escape routing. The manufacturing folks could get some insight and practice into assembling the package on package processor / memory combination. design cycles are short enough as it is. Companies that want to use the Ti processor get professionally designed short-cuts. Ti gets to sell more processors quicker. Everyone wins.

Duane Benson
It doesn't mean destruction

Reference Designators

A while back, I wrote about reference designators relative to family panels. Family panels can cause problems because often times, each individual circuit layout will have reference designators that start at the same place.

For example, circuit A, down in the lower right corner of the panel, will have resistors R1, R2, R3... Looking at the other three circuits on this hypothetical family panel, all of them also start their reference designators with R1, R2, R3... That's bad. It can lead to confusion and wrong parts on the board in the wrong spots. If we see this here at Screaming Circuits, we may spend some extra time and sort through it manually or we may ask you to fix it first. Fixing it here is a labor intensive and risky process. It's bad news.

Anyway, to the point of this post: In the original post, I listed one wrong way and three right ways. There are two other wrong ways not in the original post, which I'll list here.

Wrong way number one: R1-1, R1-2, R1-3. Bad. Most assembly software will interpret a dash as meaning a range. It will see "R1-3" as equalling "R1, R2, R3". That can be bad.

Wrong way number two: Leading zeros. Don't do "R1, R01, R001". The leading zeros are stripped and that can cause all of those the be seen as "R1". Just don't put leading zeros in your reference designators.

Duane Benson
Corrigan says Long Beach is actually in Ireland

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