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Struggling with soldering PG-TSDSON-8

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I'm struggling with soldering the PG-TDSON-8 package and wanted to ask for some tipps.

- I have a PCB designed in easyeda and ordered from JLCPCB.
- I use the solder paste SMDLTLFP (Chip Quik Inc. ), which only needs a low temperature
- I use a hot plate and monitor the temperature / time by hand

PG-TDSON-8 is a real pain. Spacings are tiny and you have no chance for visual inspection as there are no legs.Well, you see something, but only a small portion of the solder pads. There is no chance to use a DM for trouble shooting.

Soldering (in my case a mosfet) is just a lottery. I managed to get one right but with several items on the same board, chance for errors is huge.
I don't have a microcope yet, but if I inspect the footprint on the PCB by eye, I doubt that the spacing between the solderpads (0.3mm) is correct. At least the variation is obvious.
Is the PCB quality from jlcpcb not sufficiant for those tiny spacings? SOT23 and 0603 resistors work perfectly.
Should I try a different solderpaste?
Do I need a special coating of the PCB or for the solder pads?
What else can I improve?

Unfortunately the specs I need are mostly only available in tiny packages which are not ideal for prototyping.

Thanks for your help.

Are you sure that’s the right package designator? The PG-TDSON-8 is a pretty big SMD package (about 5x6mm) that’s easily measured with a multimeter, since it has exposed “stubs”, and whose legs are 0.5mm wide on 1.27mm pitch (0.77mm space between legs). Doesn’t sound like what you’re describing.

Please verify that, and provide more info like part number, image of the PCB etc.

Agree. Apart from the large pad (but should not be an issue if you're using solder paste and a hot plate), this is nothing special. Pin spacing is 1.27mm. How much bigger would you like it to be? ;D
And the pins slightly stick out, so you should be able to touch them with a small probe for testing.

Might you be getting incomplete wetting due to the extremely low temperature required?  Or conversely, you can cook that thing to high heaven before melting the plating (pure tin?), by which time whatever flux comes with that paste should be long gone.

The only thing special about DFN/SON is, you need x-ray to properly inspect the center pad.

For hand placement as in one-offs or rework, either:
- Tin the pads beforehand, being careful to apply a minimal amount to the center pad (or use solder wick to remove excess).  Do not tin the component (although in extreme cases, working with old stock components say, I suppose this might be necessary.  Be careful to remove excess solder.)
- Apply flux liberally.
- Preheat the board if necessary: copper planes rapidly spread heat away from the active area, so heat the general area, add blankets to trap more heat around the board, preheat it in an oven or with a proper preheater, etc.  Be patient: expect a heavy board to take some 10 minutes to heat by hot air alone.
- Place the component, freshening up flux if necessary, and apply hot air until the area melts.  The component will slump down and latch in place.  Give it a nudge to seat in place; push it down and around to confirm that it has an adequate volume of solder and that all leads are making contact.  (A toe fillet is sufficient for inspection purposes, but more the merrier.)  If excess solder squidges out when you push it down, try to remove the excess with an iron and wick, or push it aside with tweezers etc.

Or for reflow:
Without all the fiddling around (and perhaps without enough clearance from nearby components to be able to nudge and inspect it as above), you simply need clean surfaces, good paste and a proper heat cycle.  The above has hints at any reason it might fail: oxidized or poorly prepared surfaces, inactive or dry flux, uhh incompatible alloys I suppose (but, the bismuth stuff should be fine still, I mean it contains tin already and most component platings are tin), and too low (doesn't flow) or too high (cooks flux before it has a chance to work; oxidation accelerates) temperature for not enough time.

Note also that bismuth oxidizes faster than lead and tin, and at the much lower temperature you need a special higher-activity flux to keep it moving.  If you have joints going dry for some of the above reasons, you can't really reflow it by applying regular flux and giving it another go.


The package naming is confusing and not clear for me. The MOSFET i try to solder is only 3x3mm: https://www.infineon.com/dgdl/Infineon-BSZ0905PNS-DataSheet-v02_00-EN.pdf?fileId=5546d4626fc1ce0b016ff0a527b0515c

What I forget to mention is that I use a stencil to apply the solder paste.
I‘m currently in holidays, will read the thread again when I‘m back.


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