Actual Assembly Yields -- 0402 vs. 0201 / 01005

Question

I've been designing boards mainly using 0402s. I can hand solder 0402s all day with a microscope and some tweezers. Our passive supplier (a random Chinese passive company) has told us to get ready to switch to 0201s. They are going to phase out 0402s, in a year.

We are starting work on an IoT device, and this device is going to be going in front of venture capital folks to drum up investor money. This seems like the kind of device we need to look at 0201s and GULP 01005s.

I understand more expensive chip-shooters are rated for smaller components, but that is no guarantee of real world results, 01005s are soo tiny...

Ignoring any cost differences, has anyone noticed a significant decrease in board yields when moving to smaller parts?

Can anyone who has moved boards over to 0201s and 01005s provide any anecdotal evidence on how their production yields were affected by moving to such small pats from 0402s?

Get ready to replace those 01005s by hand, fun times...!

Answer 1

Our passive supplier ... told us ... to switch to 0201s. They are going to phase out 0402s

The real problem here is the supplier, not 0402s going away. There are plenty of companies that make, and will continue to make, 0402 and larger resistor packages. There are also plenty of assembly houses that can handle, and will continue to handle, 0402 and larger. Resistors in 0805 package are still quite common. You've apparently found one, but I haven't run into a vendor nor assembly house that can't or won't handle them.

Switching technologies because this one supplier is dropping something is the wrong reason. Switch if you need the small size for your purposes. Otherwise find a real supplier.

As for the reliability, that depends on the assembly house. There is no reason 0402 and 0201 resistors can't work perfectly well if the assembly house is competent. Pretty much anyone can slap 0805 parts on a board. Starting at 0402, the process needs to be better controlled to avoid failures, but that is certainly doable. You should give the assembly house a tester, and they only deliver you units that pass the test. Failures are on them.

At 0402 and below, you also have to think about temperature balancing between the two pads of the part to avoid tombstoning. Reliability isn't all just someone else's problem.

Another issue is the power dissipation. With 0805 parts, you can largely dismiss power dissipation limits for ordinary signal circuits. For example, 5 V across a 1 kΩ resistor causes 25 mW. That's nothing for a 0805 package, which can usually handle 125 mW. It starts getting significant for tiny packages. When using really small parts, you have to think about power dissipation in cases you might be used to just dismissing it out of hand.

However, none of this should keep you from using 0201 when there is good reason for them. One supplier of the many many out there dropping 0402s is not a good reason.

Answer 2

So I have built thousands of boards in full production with 201 parts and haven't seen a problem. In fact if my assembler told me they were having yield issues with 201s I'd probably fire them. We have much more complicated BGA packages in our system than some little two terminal parts. My reliable US assembler tells me they have no problem with 01005s but I haven't used them yet. One reason is their incredibly low power rating of 1/32 of a watt. Plus they're like tiny specs of pepper so I'm sure they're fun to rework.

Random China supplier is never a good thing. I know our shops over there like to use Walsin and they've been pretty good so far.

I've been in front of VCs/Angels many times. If you meet one who can ask you about 201s vs 402s I would be shocked.