Screaming Circuits: May 2009


June Special

Hi all;

It's time for our June special. Save up to $200.00 off your turn-key parts order. Send us a turn-key or partial turn-key order and we'll pay for the first $200.00 of your parts and or pcbs, up to a maximum of $200.00.

Try our turn-key service out and see how convenient it is for us to take care of that service too! And, yes, you can use this special on more than one order. You can use it on all of your turn-key and partial turn-key orders, as long as the order is placed before the end of this June.

How to get the special: If you place a turn-key order online, simply write "June Special" in the special instructions box. When we quote parts and boards, we'll apply the discount. If you call the order in, tell the sales rep that you want the June special.

Offer Expires the last day of June, 2009. Order must be placed with us by 11:59 pm, June 30, 2009. Good for up to $200 off of parts (includes parts and pcbs we order) on turn-key and partial turn-key orders.

PCB Layout, the Screaming Circuits Way

Our mission has always been to make your job easier. First we've got our flagship Prototype Assembly service. We have our short-run production for the next step toward getting your product to market. We have our partners, Sunstone.com, to fab your pcb. That's prototype, one step after and one step before.

 Now, we've introduced pcb layout - the next step earlier in the process. Go to our Service/layout page Layout snippet(also found at layout.screamingcircuits.com) and get a quote with just three data points: Your number of components, nets and nodes.

Our Design Engineering Group has been providing design and layout services for many years. We'll use their expertise in pcb layout combined with our speedy service approach to get you an instant quote and a great layout quickly.

For more details, read the PCB layout FAQ and our PCB layout terms and conditions.

Land Patterns and Component Spacing

One of the biggest causes of challenges with assembly these days seems to be component spacing, as I wrote about here.

We reference IPC spacing guidelines from time to time. Like, we'll say: "use IPC spacing guidelines" and stuff. That's all fine and good - unless you don't know where to go to find the IPC IPC LP viewer component spacing guidelines.

IPC-7351 is one of the things you're looking for. The IPC even has a handy dandy piece of software that you can download here at ipc.org or here and PCB Matrix.

I'm not sure how current their libraries are and if they have super new things like I covered in this post or this one, but I'm sure you can use similar parts to get pretty close to good spacing.

If you can't figure it out from there, a 20 mil courtyard is generally a pretty good rule of thumb.

Duane Benson
The best way to find something is to actually look for it.

Embedded Passives

Usually when I hear talk of embedded passives, the subject is concerning resistors and capacitors created by essentially laying down specialized layers of a specific metal or resistive compound connected to traces in an inner layer.

TI ESD CSP 007 symbol I ran across this silicon part from TI that's designed to be embedded into PCBs (TPD2E007YFMRG4). Actually, it can be both embedded or placed on top like a miniature BGA. It's a 0.8mm x 0.8mm chip scale part with four 0.4mm pitch bumps. The package height is only 0.15mm so I'd call that pretty thin. It's a two channel ESD protector with a breakdown voltage of 14V, protecting up to 15Kv.

Trying to take these pictures was interesting. That's a paperclip next to them, by the way. Every time I'd get them lined up the way I wanted them, I'd bump them or breath wrong or something.

TI ESD CSP 007 cropped 

Now all I have to do is figure out how to get the little things back in the cut strip. Or maybe I'll just brush them on to the floor and they'll blend into the carpet.

Duane Benson
Don't despair, it's still 800 times bigger then the Proteus

Keep Out Area 51

According to the glossary on the Maxim website, a "Keep-out zone/area" is defined as:

"The area on or near a CPU or GPU processor that the circuit board layout design can not use, due to thermal management components, cooling, and mounting constraints."

In the efforts to shrink boards down or get the bypass caps closer to high speed parts, it's becoming more and more common to see components located closer and closer together. This is all good up to a point.

Sometimes, it's obvious because the two components just don't fit, as in the close up of the TO-220 andKeepout actual overlap capacitor here. Sometimes, though, it's not so obvious. Violating spacing rules may lead to solder bridges or thermal problems, not to mention mechanical troubles.

Many, but not all, CAD library footprints have a keep-out area specified in addition to all of the other layers. Well, in theory, they should have the keep-our area specified. I bet most don't though.

Keepout areas On the caps in the PCB drawing here, the outer red box is the keep-out zone. Nothing should be in there except the trace going to the part. You might possibly actually be able to place all the parts on this little board, but there are several spots likely to get bridges or have component interferences. Regardless, you could not expect this example to be reliably manufactured anywhere by any method.

Too tight component spacing is one of the most common issues we're seeing these days. I know you need to keep the board small, but for a reliable assembly, respect those keep-out areas and get out your IPC book if you have any spacing questions.

BONUS POINTS: I have a lot of parts spacing issues in the little CAD drawing as well as some other boneheaded moves. The first readers to point out each of the three other big mistakes will get a 10% discount code for use on your next assembly order. Email your answers to me at: dbenson@screamingcircuits.com.

Duane Benson
Everybody was kung foo fighting
Those kicks were fast as lightning...
I don't know why, but I've got that song stuck in my head. Ugh.

Tuesday, Tuesday, Tuesday!

UPDATE: It's now live! (May 5, 4:45pm) Quote your short run job online


What's so important about Tuesday? Well, I'll tell you what's so important about Tuesday.

We're making our website better and at 4:00 pm, Pacific Standard time, our website will be offline for a bit. It could be as little as ten minutes or as long as an hour. We'll do our best to keep it quick, but just in case, if you need to get an order in on Tuesday afternoon, be aware that the site will be down briefly.

You can always call in your order, toll-free at (866)784-5887 during that time (or any time, actually).

And, why, you might ask are we doing that? Well, if you've been following new things from us, you've heard about our new short-run production service. We've been offering it over the phone for a bit. (see more details here). We're adding on-line quote and order for short-run production to the web site on Tuesday. Cool!

So, even if you don't have an order to place or a job to quote at 4:00 pm PST on Tuesday, May 5, check back after 5:00 pm and see what's new on our quote engine!

Duane Benson
Chips & salsa, please

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