Godamned 0603

fredag den 18. februar 2022 kl. 09.32.02 UTC+1 skrev Sylvia Else:

also 0402 metric which is 01005 imperial

Designed to confuse. Why do people do that?

Jeroen Belleman

Marketing! There is a special caliber to check that and you should by it:

Olaf

You mean why do people use the measuring system that everyone else in their country use? I guess this is a more pointed question at the US community. I remember working with a mechanical engineer at a military contractor and was surprised they still did everything using inches. 90% of electronic components are in mm as the primary unit. I guess I expect the mechanical community would have converted by now, but, no.

I seem to recall an imperial 0603 is a metric 1608. The places where I would be selecting a part they make it clear which size they are using. On layout I would notice the difference in size, 2.5 to 1. I'm a bit surprised this error was made. If the layout was done by someone else, maybe not so much. I like doing layouts. It's like puzzle solving.

I don't get why mil are still used in PCB layout so much. Layer thickness is still done in mil. Trace/space is still commonly in mil. I typically do my layout in mm. 6 mil is 0.1524 mm, so that gets rounded to 0.15 mm. Unfortunately that can trigger the alarms at PCB house pricing software and put you in a higher price category. I remember seeing feature checking software that would sound the alarm at what I can only assume was round off error missing the target by 0.00001 inches or something. I don't think I ever used that PWB supplier. I can't imagine what it would take to get that through their system. There were dozens if not hundreds of such error reports.

For a thousandth of an inch, we say 'thou' (with the th as in thousandth). A mil is often verbal shorthand for a millimetre or millilitre, depending on context.

That has caused much confusion too.

The power numbers in that chart are not definitive. Different companies rate them differently. I recall one part I was using because it had much higher dissipation in a small package. Then it was discontinued! But others had similar parts by then.

Because it's 1 to two digit small integers for all the practical sizes on a board. The millimeter/micrometer sizes are all off by at least a factor of ten to be convenient.

metric pin headers/screw clamps are also sh!t it works to have 2 pins 5.00mm in 5.08(2x100mil) holes. but when it's 8 pins long or so it won't fit anymore. (perfboards!)

Sorry, what is convenient about 250 mil? Or 850 mil, or 4500 mil? I'm good with 6.35 mm or better just 6 mm for a mounting pad. My board is 21.6 x 114 mm in metric. I don't find that cumbersome although I probably would have made it 21.6 mm (required by the application) by 110 mm (selected by me).

I haven't used a perf board in 20 years. I also don't typically use through hole, although it does show up for cable connectors for ribbon cables. In that case, 2.5 mm spaced connectors are not an option. I didn't know they made them. I've seen 2 mm and 1 mm, but 2.5 mm??? What are these 5.0 mm connectors, more than 8 pins long? I'm guessing something that might be used in a washing machine sort of appliance?

Your PCB layout program library (or person) must be ambiguous.

Since SMT originated in the USA, at IBM, everyone could have kept the original size nomenclature. Or at least done something original if they insisted on going metric, like 06M03 or something. An M8 screw is clearly distinct from a number 8.

I like to use 0805s. 0603s are getting too small to handle and probe. I recently used some 0402s for some really fast stuff, and I hate them. Metric 0602 is 0201 in plain English, spec-of-dust size.

Most passive are made on 20 mil thick alumina, so the small ones tend towards cubes.

Did you use reference designators? That would have made the size difference more obvious.

The early IC designers defined as inch as equal to 25 mm.

I don't see 0603 used as a label for metric sizes. Digikey clearly lists (0603 Metric) as a size. Data sheets seem to use 0603 as a label for 1.6 x 0.8 mm parts. I'm not finding the confusion issue.

The point is not whether we should use metric or inches. The point is that the /syntax/ of the size designators should be distinguishable. Without further indications, I would assume that 0603 is imperial.

Jeroen Belleman

fredag den 18. februar 2022 kl. 17.06.53 UTC+1 skrev snipped-for-privacy@highlandsniptechnology.com:

since it is now standardized as 25.4mm, pretty close

Am 18.02.22 um 17:02 schrieb snipped-for-privacy@highlandsniptechnology.com:

At a customer's, the solder ladies bragged they could solder everything. I showed them my Murata 01005 starter kit. Oh what a shock!

Ger "the bags are all empty" hard

I find that passive data sheets all have dimensional data. Even with the same designation without the confusion of metric/imperial, parts vary in size. I select a pad size that is appropriate.

Not so fast there. Too Euro-centric?

In the US, traditionally a "mil" is 0.001", and a "tenth" is 0.0001", and a millimeter is a millimeter ("mm") and never a mil.

Joe Gwinn

Pre-NATO, all US military machinery would have been inches; even now, NATO has standard 7.62 mm ammo, which is just a soft-conversion from .30 caliber...

Conversion is a slow process. In the print industries, inches have been the norm; in science, it has been SI (metric) units for decades. So early semiconductor designs had diffusion depths in microns, and emitter areas in... square micro-inches. Because the emitters were printed.

Eventually it gets sorted out... but I've got a century-old machine tool that has inch-standard parts everywhere except one lefthand metric screw... so don't expect the conversion-in-progress phase to be complete in your lifetime. Digitization, if anything, will impede the progress; your calipers are made with a 'convert to' button, so the multiple standards don't bother one so much.

or it might help, if all your tools/machines/instruments can only do one standard switching means throwing it all away. If they can do both like every CNC or digital caliper switching is just a push of a button