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Struggling with soldering PG-TSDSON-8

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T3sl4co1l:
That particular attempt looks fine, yes.  The solder balls aren't great, and it's not clear how much wicked into that via (evidently not much). That might just be process variation.  Doing another dozen or so would give, at least a starting point, as far as statistical samples go.

Tim

tooki:

--- Quote from: T_guttata on November 16, 2021, 08:00:14 pm ---I posted a picture where you precicely see, how much solder there is. Is this really too much???

--- End quote ---
I think so. But it’s easy to test: stencil it on, then use a curved scalpel blade to carefully remove some paste before placing the component. For example, try removing 1/3. Then see how it reflows.

Since you have a microscope, you don’t need to rely on a full fillet on each pin to ensure it’s connected: use the microscope to look at the joint from a diagonal. You should be able to see whether it’s flowed to the pad and pin.

T_guttata:
I tried again with a different solder paste, but unfortunately it does not really look better?

I don't have a scalpel blade to try to remove some solder. The stencil was way more expensive than the actual PCB and therefore I would assume, that it actually works.

What's usually the thickness of the stencil? Maybe jlcpcb does not a good job in this regard?

Anyway, I will certainly switch to a LFPAK56 footprint. I want to be able to solder it correctly with 99% chance, otherwise I only end up debugging.

Maybe I could also order a fully assembled PCB from https://www.eurocircuits.com/? I just did not find any price indication for assembly.

tooki:

--- Quote from: T_guttata on November 19, 2021, 07:19:03 pm ---I tried again with a different solder paste, but unfortunately it does not really look better?

I don't have a scalpel blade to try to remove some solder. The stencil was way more expensive than the actual PCB and therefore I would assume, that it actually works.

What's usually the thickness of the stencil? Maybe jlcpcb does not a good job in this regard?

--- End quote ---
Stencils are intended for precision application in multi-thousand-dollar paste printing machines. They were never intended for manual use. Chances are you think you’re using it properly, but aren’t. (Using stencils manually is HARD. I was just talking about that the other day with a guy at work — a literal graybeard who started working in electronics before I was born — because of some difficulty he was having with getting clean paste prints for some components. And that’s with expensive European-made boards and stencils. It’s very hard to support a stencil properly when using them manually. They need high rigidity by being mounted into frames under high tension, not flopping around.)

Tiny parts with tiny pads simply leave no room for error. The tiniest slip and you get paste under the stencil, which raises it up and increases the amount of paste applied.

Honestly, the last picture there doesn’t look bad at all. But yes, if a larger package is available and PCB space allows, use it, as it will make your process more predictable and easier to inspect.

FYI, with JLCPBC stencils, the vast majority of the cost is shipping, due to the dimensions of a whole stencil. But you can apparently ask them to cut the stencil down to size for manual use, allowing it to be shipped in the box with your PCBs.

T_guttata:
I was looking for very low Rds_on mosfets smaller than the TO220 package and ended up with this PG-TSDSON. The TO220 package would be too big, but the LFPAK56 is 5x6mm and totally fine. I will try it.


--- Quote from: tooki on November 19, 2021, 08:00:04 pm ---Stencils are intended for precision application in multi-thousand-dollar paste printing machines. They were never intended for manual use.

--- End quote ---

I doubt the package size of 3x3mm was designed for hand fabrication^^


--- Quote from: tooki on November 19, 2021, 08:00:04 pm ---
FYI, with JLCPBC stencils, the vast majority of the cost is shipping, due to the dimensions of a whole stencil. But you can apparently ask them to cut the stencil down to size for manual use, allowing it to be shipped in the box with your PCBs.

--- End quote ---

Yes, I already reduced the stencil size until it does not increase shipping chost. $2 for 5 PCBs, $7 for the stencil and approx $20 for shipping^^

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