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SMD footprint insanity?

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I'm trying to purchase some caps and resistors for line termination and bypass. I don't know if it's me or what but it seems like package names are mixed with the actual. That is, imperial and metric are both used. Worse is that most exist in both as the same name.

0402? Is that metric or imperial?

0402 (1005 metric) : 0.04" =D7 0.02" (1.0 mm =D7 0.5 mm) Typical power rating for resistors 1/16 Watt

01005 (0402 metric) : 0.016" =D7 0.008" (0.4 mm =D7 0.2 mm) Typical power rating for resistors 1/32 Watt

It's even worse that they are "inverted". Not sure how they get 01005 out of .015 and .008...

Mouser doesn't even always add the dimensions to know absolutely. Similarly the footprints in my EDA package use those numbers without knowing which(and I inadvertantly chose a 402 package thinking it was metric but for some reason it was just as large as the 0603 imperial).

This is really insane and I guess someone did this in purpose just to screw with people? Why not add some differentiating character such as

0402i or 0402m? Life sure would be easier?
Reply to
Bobby Joe
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Imperial. Most stuff in Electronics is traditionally Imperial, like 0.1" pitch components, 'cos the Americans dominated the discipline in its formative days.

You have much to learn about Americans.

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Nemo
Reply to
Nemo

Better yet, why not just make "0402" the name of the package size and stop trying to make two different names.

Reply to
MooseFET

Track down the manufacturers data sheet.

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Reply to
Hal Murray

Good idea. You always end up needing to look up e.g. the precise dimensions of the recommended pad when designing a footprint.

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John Devereux
Reply to
John Devereux

Are you saying that back when we advanced the industry (not merely "the discipline")by leaps and bounds, that we should have been considering the rest of the world's standards of weights and measures, etc.?

You're a real prize.

Reply to
life imitates life

METRIC IMPERIAL

0603 (0.6x0.3mm) 0201 (.02x.01inch) 1005 (1.0x0.5) 0402 (.04x.02) 1608 (1.6x0.8) 0603 (.06x.03) 2012 (2.0x1.2) 0805 (.08x.05) 3216 (3.2x1.6) 1206 (.10x.06) 3225 (3.2x2.5) 1210 (.12x.10) 3720 (3.7x2.0) 1408 (.14x.08) 5025 (5.0x2.5) 2010 (.20x.10)

RL

Reply to
legg

Welcome to the world of PCB design! That's why the EDA packages have a magic Metric/Imperial hot key. I use it

100 times a day.

Imperial

Yes, it really is annoying, particually with 0402/0603/0805 R/C's, Case-A/B/C/D caps etc. I still use the imperial numbers and letters for these as these are what I've been used to over the decades. The IPC who basicially run the PCB standards have tried metricate everything. Good in some places, really annoying in others. Most SMD parts these days are metric though in terms of pin spacing etc, so makes sense to go metric from that perspective.

Dave.

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Reply to
David L. Jones

How do these relate to package designations? I see SOD-23, SOT-123, and all kinds of other packages called out on, say, Digi-Key and stuff.

Oh, never mind. RTFDS. ;-) (makes it kinda tedious to spec a part for a certain size.)

Thanks, Rich

Reply to
Rich Grise

This may help.

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The table covers only smaller semiconductor packages used for bipolar transistors and mosfets.

You really do have to check data sheets when confirming physical compatability. A vendor can only really convey the surface info provided by the mfr, and terminologies differ.

Substituting for more complex devices nowadays may just be wishfull thinking, as second sourcing is no longer considered to be in a semiconductor mfrs best interest.

RL

Reply to
legg

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