The complaint I get about 0402s is tombstoning. They are practically cubical in form factor, so the surface tension of the solder has a lot of lifting power. Maybe our PCB footprint isn't ideal, but we just avoid them. I like reference designators, so a really small part doesn't save much room.
0603s, or even 0805s, are fine down to maybe 100 ps edges. I'm toying with 35 or so now.-- John Larkin, President Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Except in some really tough places, we managed to get all of the reference designators onto the boards. They weren't always right next to the components, though. A row of resistors might have an equivalent row of reference designators a 1/4" away.
The issue isn't usually speed, rather size and cost. Some low-value capacitors aren't going to be available in 0603s, anymore (according to Murata).
In the realm you claim to design 'advanced' circuits for, you would be wise to gain expertise in miniaturizing all of it.
You will be left behind by those who do, and their gear will be an order of magnitude better in performance and quality than yours.
It is already true.
That is where you are/have headed, dork.
An order of magnitude performance difference between 0603s and 0402s?
AlwaysWrong.
What a dim bulb, DimBulb.
No, idiot. Between decent work, and that crap conglomeration he calls an assembly.
Fuck off, Willioams. You are out of your league.
The only chime a retard as pathetic as you can muster.
You are truly sad. You didn't get that argument right either, loser.
IOW, you haven't a clue what you're talking about. Not one in the crowd is surprised.
THAT is for sure, AlwaysWrong. I don't play in the hamper league.
Facts *are* facts. You *are* AlwaysWrong.
AlwaysWrong.
We don't need to keep our stuff very small, or to keep it low power. Those don't matter to our customers. The picosecond stuff is inherently tiny... it has to be to be fast.
An order of magnitude below 35 picoseconds? An order of magnitude above half million hour MTBFs? Go for it.
Actually, we are seeing increasing demand for precision measurement and especially for precision timing. Lots pf people are afraid of the n-word (nanosecond) and terrified by the p-word (picosecond)... with some justification.
-- John Larkin, President Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
But do some test before jumping in head first, and pay extra attention to an equal thermal behavior on both side during the layout. Now you have a wider "solder bath" that can exert more cantilever, plus the part now moves about the short axis where gravity will not work as well. So it may be more prone to do a wheelie.
[...]-- Regards, Joerg http://www.analogconsultants.com/
The recommended footprints work well, as long as the reflow profile is correct. If it's not, there's no telling how screwed up the other joints are too.
Tombstoning is usually a function of solder paste performance. That is usually a function of a company too cheap to keep it fresh. So old paste does not perform the same, and parts can reflow on one end, and get 'popped' on the other due to a flux problem with the paste.
An additional pain is the new RoHS processes. Many times, there is even less paste stenciled than the leaded process had, and the temp profiles climb higher as well. Even worse for the flux.
The key is that the solder has to melt before the flux boils out so that the surface tension can retain the part. So the RoHS profiles _and pastes_ are even more critically managed.
The way you were dissin' mini-circuits yesterday, you should be drummed out of the business.
What are you talking about? I said that the inexpensive MiniCircuits bias tee is very good.
-- John Larkin, President Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
AlwaysWrong.
Always!
-- John Larkin, President Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
No kidding! We had a problem with loose solder balls under some components & tombstoning. We fixed it by switching to a finer grade of paste solder & a new reflow oven with more zones that allowed us to refine the profiles. With the Heller oven, all the operator had to do was scroll through the stored profiles to find the board they were running.
-- You can't have a sense of humor, if you have no sense.
It's far worse with RoHS because you're really in the corner of over-temp and the solder not reflowing. There isn't any margin. The temperature profile has to be just right. We got it done with a four-stage oven but things were
*much* better after they installed the 12-stage oven.
are
They were just investigating lead free solder when I left, but every item built there was connected to our Telemetry products so I'm sure they were exempt.
-- You can't have a sense of humor, if you have no sense.
are
Despite the fact that decades of science get thrown out when they get rid of 63/37, even exempt gov circles, etc. are beginning to find that simply embracing the RoHS processes which were shoved down our throats ends up being cheaper than constantly having to send already produced chips back out for "re-balling", etc.
We still use leaded for (certain) re-work tasks, as it is permitted, but our boards are nearly all lead free now.
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