Future: 0603 versus 0402 parts

Thanks. We'll give it a try and see if it helps.

John

Thanks! Here's the old one (1.5 years in service so far) for comparison:

Since then, I've learned a lot (here and the geda lists) about EMI, which the current board suffers from. I'm hoping the new board is much more tolerant of the messy environment it's in.

Perhaps, but I don't have one of those. I have a Metcal Talon with the pointy tips, but they're way too big for 01005s, so the few times I had to remove one I just sucked it up with an iron or copper braid and put a new one on.

Actually, I use a lot of 11x14 fanfold paper for assembly program listings. I'll go through a couple of boxes of paper and a couple of ribbons for every embedded program I do. I guess that's why I said "11x14". But we print schematics on B-size sheet paper, 11x17 as MiniPrick so helpfully pointed out, on a laser printer.

John

Then show how it costs the same as using a SMT process that is automated. Hint: even pin in paste is still more expensive.

They only respond to company level, bottom line, profit/loss numbers. That is what they are taught in MBA school. Your only chance is to show it to them that way. Set it up, present it, and get back to us with the results.

Un bel giorno Jeff L digitò:

Of course, and this usually means BGA. BGA is superior to QFP in each possible way (dissipation, routing, signal integrity...), the only drawback is the impossibility to hand-solder it properly.

If they don't then there's the perfect business opportunity: A micro brewery. That is what a Monsanto engineer did, except that he preferred wine and started a winery.

It has to be a mindset. Laws and regulations of the more bizarre kind such as RoHS and WEEE don't change behavior. I am similar, keeping every piece of metal. Same with wood BTW. Anything that doesn't have paint or glue on it is saved for the next winter to start the wood stove. While doing yard work any twig thicker than a pinkie is also saved. We use a black plastic composter as a kiln for that.

That's why I was asking, thinking that there ought to be whisker-induced system failures by now. Or maybe it turns out not to be that bad after all. But I have seen too many whiskers myself under a microscope to be that optimistic.

And I am pretty sure the politicos didn't have the foggiest idea about such consequences.

drawback

And a 4+ layer board in most cases!

Actually, BGA's are not that hard to put down with "primitive" equipment! Temperature controlled hot air (modified heat gun in holster?) with a hotplate works quite well, or in pinch / low budget scenario an old toaster oven works, but they work better with some more advanced temperature controls. Of course you wouldn't want to do that for production boards but for a one off prototype, it can get the job done.

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More likely that the problems haven't hit yet, but then again the average lifetime of consumer crap has been reduced to a couple of years so it's likely that they wouldn't even notice the problems with lead free. Swatch had a big problem with lead free and tin whiskers in their watches (tin dendrites likely would not have formed in that scenario, as that requires moisture as the driving force). There are documents of satellites becoming crippled or useless due to tin whiskers forming from tin coatings. This has been documented for decades, and the telecom industry had tin whisker problems back in the 1920's - 1930's - the answer was to put lead the solder.

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Or they also wanted a very temporary boost in the economy due the enormous money spent on changing processes, new legislation to be written, and the sales increase for the assembly equipment to handle lead free (in which many SMT and through hole machine manufactures are suffering or out of business from the approx year 2000 industry crash, and the now massive outsourcing of work to cheap labor places like China).

Oh how I'd love to be able to do splines in CAD.

robert

And this from someone who shuns parts that don't have a SOIC->TSSOP migration path. That 331 must cost you a lot of sleep.

robert

I did, at first. But upon further research (before releasing this design) it turned out that this chip almost cannot be called off because it is in lots of industrial and military products that must remain in production until I put my teeth into a jar. I watched the stock a while and Digikey always had around 2000 of them on hand which is generally a good sign. They are expensive but if you need V/F, what choice other than a uC is there?

Both are OK for common design. Using 0402 means you haven't too many BGAs onboard. Else you need 0201. 0402 could be manually soldered. I've solder desolder many of them in small prototypes series ( 10 to 20 pcs of PCB)

I suggest either 0402 with at least 0603 pad size for test points or

Vasile

No BGA. I don't like them. It's mostly TSSOP and, where I can get away with it, SO.

I am leaning towards 0603.

I'm growing positively fond of BGAs. An FPGA with a few hundred I/Os can be liberating. On-chip resources (a bazillion gates, multipliers, LVDS transceivers, clock managers, dual-port ram) are great, and internal interconnects are free, saving a lot of pins as compared to splitting up the functions into several smaller chips... it's like getting a blank check.

Our production yield on soldering BGAs thus far is still 100%, which is a lot better than for fine-pitch leaded parts. And we save a lot of inspection time, since we can't inspect them!

John

I've been using 0603 as my 'default' for years, but I'm seeing others, especially high-volume manufacture, defaulting to 0402 more and more.

For very high volume consumer products designed in China, 0603 is still preferred. for cellular handsets, 0201 and 0402 only ... some even smaller.

Frank

On Sun, 25 Mar 2007 10:23:41 -0800, John Larkin Gave us:

But don't know the first thing about cleaning the assemblies correctly, or economically! You are one of those idiots that glosses over all the tasks you consider menial.

IT IS BROKE, YOU SHOULD FIX IT.

Both your process and your fucktard mentality!

We used to do that on hybrids. Pull-ups weren't trimmed at all, others to 1% or whatever needed. The really nice thing was active laser trim where you could trim the response of an RF circuit to perfection. I miss them days. No caps beyond a few pF though, just like with chips.