Using 0402 when plenty of room for 0603

[Faringdon]

thanks, ayk, its much easier to tweezer_grab an 0603 than an 0402

[ebastler]

Never yet seen a "head on pillow" 0603......seen many H.O.P 0402...

Umm... I thought the "head on pillow" defect is specific to BGA packages. If the BGA's solder ball and the solder paste on the board do not fully melt and coalesce, the BGA ball forms a "head" which rests on the "pillow" of solder paste. What do you mean by a "head on pillow" problem with 0402 resistor packages?

[Faringdon]

thanks, H.O.P. is like the 0402 res is lying on the pads...and looks properly fitted from a distance, but if you get the magnifying glass...you see one of the pads is lying on top of the solder, and is not melted into it.
Seen this on loads of production failed boards.

[Niklas]

I work with an automotive design with 0402 sized resistors and capacitors mounted on both sides of the PCBA. The footprints are minimum according to IPC 7351, dense layout, no rework and IPC-A-610 class 3 acceptance. Even with some of the components connected directly to copper polygons, there are no issues with tombstoning. The key is to have control of symmetry between the pads and check the solder pad recommendations from the different alternatives. Some of this can be handled by adjusting the solder mask to define the effective pad size on the polygon end to match the copper defined pad.

[tooki]

thanks, H.O.P. is like the 0402 res is lying on the pads...and looks properly fitted from a distance, but if you get the magnifying glass...you see one of the pads is lying on top of the solder, and is not melted into it.
Seen this on loads of production failed boards.

So simple non-wetting.

There are many things that could cause that, none of which are specific to 0402 parts.

[Faringdon]

The key is to have control of symmetry between the pads and check the solder pad recommendations from the different alternatives. Some of this can be handled by adjusting the solder mask to define the effective pad size on the polygon end to match the copper defined pad.

So you are saying that 0402s are ok, as long as you go through the layout, and adjust the polygon side pad so its solder mask defined.......that tells me that 0402's are  "with difficulties".

[Infraviolet]

One other point to add, which hasn't been mentioned yet.

In terms of PCB routing 0603 can actually be easier to work with, with common design rules for trace spacing and minimum width (0.2mm for each) it is very easy to route under an 0603 between its pads (0.9mm gap), not feasible to route under an 0402 (0.5mm gap < 0.2clearance+0.2width+0.2clearance). 0603 has the advantage here then, when you've got boards with two (or one) copper layers, and a board house with 0.2mm design rules.

My own circumstances are that I use 0603 mostly, for ease of hand-assembly, with 0805 for anything polarised like SMD LEDs. But unlike most of the arguments in favour of 0603, this one about routing underneath still holds for machine assembled boards too.

[asmi]

So you are saying that 0402s are ok, as long as you go through the layout, and adjust the polygon side pad so its solder mask defined.......that tells me that 0402's are  "with difficulties".

The only one who seems to be having difficulties is you. I have assembled 100's of boards with 10's of thousands of 0402 parts, and I only ever got a SINGLE case of a tombstone (and one 0201 tombstoned on another occasion). Heck I get more soldering problems with QFNs than with 0402 (or even 0201)!

[asmi]

One other point to add, which hasn't been mentioned yet.

In terms of PCB routing 0603 can actually be easier to work with, with common design rules for trace spacing and minimum width (0.2mm for each) it is very easy to route under an 0603 between its pads (0.9mm gap), not feasible to route under an 0402 (0.5mm gap < 0.2clearance+0.2width+0.2clearance). 0603 has the advantage here then, when you've got boards with two (or one) copper layers, and a board house with 0.2mm design rules.

My own circumstances are that I use 0603 mostly, for ease of hand-assembly, with 0805 for anything polarised like SMD LEDs. But unlike most of the arguments in favour of 0603, this one about routing underneath still holds for machine assembled boards too.

That's yet another argument from the past Take a look at the calendar, it's year 2023 now, even super-cheap low-end PCB fabs have no problems manufacturing 0.1/0.1 mm traces, JLCPCB can do 0.09/0.09 mm traces, some other affordable fab I use (WellPCB) can go down to 0.08/0.08 mm. And that is just a regular process, not HDI or other sort of special process.

[48X24X48X]

I think 0402 reflow yield is very good and I tend to like their joints more than 0603. As someone that assemble own board, I would love to use 0402 as much possible but having only a 4-head machine, it would make placement too slow as you need more nozzle variations to cover all component sizes. 6-head would be minimum, or better 8-head, or okay it never end... As it stands now, I only use them at the RF tuning circuit.

[SMTech]

I think 0402 reflow yield is very good and I tend to like their joints more than 0603. As someone that assemble own board, I would love to use 0402 as much possible but having only a 4-head machine, it would make placement too slow as you need more nozzle variations to cover all component sizes. 6-head would be minimum, or better 8-head, or okay it never end... As it stands now, I only use them at the RF tuning circuit.

This is the reason Toolchangers exist... and why I'd never buy a machine without one.

[Microdoser]

After reading this thread, I think I'll get in some 0402 resistors and gain some wriggle space on my latest board...

[ebastler]

After reading this thread, I think I'll get in some 0402 resistors and gain some wriggle space on my latest board...

Hand-placing them with tweezers is significantly more fiddly than with 0603s though, in my experience. Buy some extra 0402s to fling across the room, never to be seen again...

[HighVoltage]

After reading this thread, I think I'll get in some 0402 resistors and gain some wriggle space on my latest board...

Hand-placing them with tweezers is significantly more fiddly than with 0603s though, in my experience. Buy some extra 0402s to fling across the room, never to be seen again...

The way I do this:
- Apply some solder paste to the PCB pads
- Use tweezers to lay down the 0402 part carefully
- use some small angled pliers and lay down one wing on to the 0402 part (2 handles on the table)
- use the solder iron and just touch the PCB pad and it will solder right away
- repeat on the other side of the 0402 part

This has been working for me every time without flying parts across the room.

[ebastler]

- Apply some solder paste to the PCB pads
- Use tweezers to lay down the 0402 part carefully
- use some small angled pliers and lay down one wing on to the 0402 part (2 handles on the table)
- use the solder iron and just touch the PCB pad and it will solder right away
- repeat on the other side of the 0402 part

Step 2 is where I do the flinging. 

The 0402 parts slip out of the tweezers more easily than the larger parts. Depending on the amount of pressure I apply to hold them, that catapults them across the PCB, the bench, or the room... Once the part is placed on the PCB, everything is fine, both for hot-air or conventional soldering.

(Yes, I do have decent tweezers, and the majority of 0402 parts makes it to their destination OK. My loss rate is below 10%, I'd say -- but still high enough to annoy me. So I prefer 0603 for boards I intend to populate by hand.)

[HighVoltage]

(Yes, I do have decent tweezers, and the majority of 0402 parts makes it to their destination OK. My loss rate is below 10%, I'd say -- but still high enough to annoy me. So I prefer 0603 for boards I intend to populate by hand.)

I am using tweezers with 90 degree tips, so that the 0402 part is lightly squeezed in parallel.
Normal tweezers usually have an angle to the part and then they like to fly away.

Actually the best 90 degree tweezers I found for this purpose came from my daughters "make up kit" for precisely removing facial hair!

But of course, I agree that 0603 parts are easier to handle by hand.

[asmi]

Hand-placing them with tweezers is significantly more fiddly than with 0603s though, in my experience.

Not if you have the right equipment like stereo microscope and a good vacuum pickup tool (cheap crap from Aliexpress is not that). I place 0201 caps using the same equipment, though it is somewhat harder because even under 10x magnification these things are rather small.

Buy some extra 0402s to fling across the room, never to be seen again...

I buy them by reels on LCSC because they are so cheap, so even if I lose some, who cares - there are 10K parts on a reel.

[ebastler]

[...] the right equipment like stereo microscope and a good vacuum pickup tool (cheap crap from Aliexpress is not that).

I do use a stereo microscope and find it helpful -- seeing things better improves the placement precision, and I feel that the higher-resolution in the hand/eye feedback loop also gives me a steadier hand.

Which vacuum tool do you recommend? I played with vacuum pickups a while ago, mainly for hand-placing some BGA packages which were too wide to grab with tweezers. The cheap (Aliexpress style) manual tool was crap indeed. I also experimented with a home-built design with a motorized pump, but could not find a good position for the "release" hole on the handpiece: Lifting a finger to release the part would make me shift its position most of the time. So I'd appreciate a reommendation!

[asmi]

I do use a stereo microscope and find it helpful -- seeing things better improves the placement precision, and I feel that the higher-resolution in the hand/eye feedback loop also gives me a steadier hand.

Yeah, when I bought the microscope, I realized that my hands are capable of much more precise movements when I can actually see them. I use AmScope SE410 with 10x magnification for regular work, and 20x when working with 0201s or when I do solder joins inspection. I've taught my wife to solder and assemble PCBs, and she loves the microscope, so much so that she even does her nails under it now I'm planning to upgrade it to trinocular version on a dual-arm boom eventually - with a camera so that I can show my wife something under it (currently it's very clunky because there are only two eyepieces, so only one person can see at a time), and dual-arm for easier positioning of a head, but if you work alone, binocular head is more than sufficient (unless you want to make photos/videos under microscope of course).

Which vacuum tool do you recommend? I played with vacuum pickups a while ago, mainly for hand-placing some BGA packages which were too wide to grab with tweezers. The cheap (Aliexpress style) manual tool was crap indeed. I also experimented with a home-built design with a motorized pump, but could not find a good position for the "release" hole on the handpiece: Lifting a finger to release the part would make me shift its position most of the time. So I'd appreciate a reommendation!

This is the tool I use: https://zeph.com/zt3web.htm It's got multiple tips available to work with everything from 01005 to big BGAs. It's not cheap, but if you are serious about assembly, this investment is absolutely worth it! Placing small stuff with it is a breeze!

[NorthGuy]

I also experimented with a home-built design with a motorized pump, but could not find a good position for the "release" hole on the handpiece: Lifting a finger to release the part would make me shift its position most of the time. So I'd appreciate a reommendation!

I use a tee on the air hose which I can open and close with the thumb of my other hand without disturbing the hand piece.

[langwadt]

[...] the right equipment like stereo microscope and a good vacuum pickup tool (cheap crap from Aliexpress is not that).

I do use a stereo microscope and find it helpful -- seeing things better improves the placement precision, and I feel that the higher-resolution in the hand/eye feedback loop also gives me a steadier hand.

Which vacuum tool do you recommend? I played with vacuum pickups a while ago, mainly for hand-placing some BGA packages which were too wide to grab with tweezers. The cheap (Aliexpress style) manual tool was crap indeed. I also experimented with a home-built design with a motorized pump, but could not find a good position for the "release" hole on the handpiece: Lifting a finger to release the part would make me shift its position most of the time. So I'd appreciate a reommendation!

a 3/2 solenoid valve and a footpedal?

[asmi]

I use a tee on the air hose which I can open and close with the thumb of my other hand without disturbing the hand piece.

The tool that I use releases small parts automagically once they touch the board. I'm not exactly sure how that happens, my best theory is that the tip is hard enough such that as soon as part touches the board, it changes it's spacial orientation slightly and this way a small hole opens between the tip and a part, which removes vacuum and so part is no longer held on a tip. Those tips is the biggest difference between handmade tools and the one I use, they are made from some special material which prevents parts from sticking to it (common problem when handling small parts with tweezers), it's soft enough such that it won't damage delicate parts, but hard enough to allow such "automagical" release.

[ebastler]

Great suggestions, thank you all!

I actually have a solenoid valve and footswitch in the drawer which I wanted to add to my homebrew vacuum tool. Ended up rigging up a little support fixture for the pipette instead, which was helpful for the BGA placement (where one has to position XYZ and three rotational axes quite precisely -- beyond my coordination skills, it seems... I love the simplicity of the T junction though, and might try that too.

And I am intrigued by the "automagical" release idea. The zeph.com/zt3web.htm page shows Delrin tips for small parts, I assume those are the ones? They do sell them separately, but at quite a hefty price, $34.50 (plus international shipping & customs for those outside North America). I will look around a bit; found several other US distributors of what looks like the same tips, at similar prices, but none in Europe so far.

[Microdoser]

I think I'll see how my normal method works on a test board. Use a pair of tweezers that have a little residue on them from the previous component's solder paste. Not a lot, just enough to pick up a tiny resistor/cap and which sticks slightly less than the solder paste on the board does.
 
I've already accepted some component loss as a part of working with things so small. I may as well get the extra board space, and reduce part costs at the same time.
 
I assume they are as reliable as 0603?

[c64]

I use a tee on the air hose which I can open and close with the thumb of my other hand without disturbing the hand piece.

I use exactly the same. Cheap $10 vacuum pump from China (running at half voltage - more than enough suction), hose with hole and tips from crap Chinese vacuum pickup tool. Never use tweezers any more