Lead Free Solder and Pad Sizes

[john12ax7]

Does anyone find it helpful to use larger pad sizes with lead free solder? I typically use 33mil hole with 80mil pad for 1/4w resistors. Anyone use bigger pads? Thinking bigger pads and bigger tip could improve heat transfer.

I have no issues with lead free for turret board construction, or even smd. It's the regular through hole that doesn't seem to wet properly. Which lead free solder has the best wetting action?

 

[Tubetec]

Ive tried lead free a few times , without exception it didnt make bright and shiney joints , more like a pile of oxidised crud .
You could try using a little extra flux paste to help it to flow .

 

[Newmarket]

Ive tried lead free a few times , without exception it didnt make bright and shiney joints , more like a pile of oxidised crud .
You could try using a little extra flux paste to help it to flow .

It doesn't make shiny joints like leaded solder. It's not a flaw. Your description of your results sounds like you didn't get it hot enough. What tip temperature did you set ? Assuming you used an iron rather than paste/hot air.

 

[Tubetec]

Im sticking with 60/40 ,

 

[gyraf]

I'm all in on SN99.3/CU0.7 - e.g from Stannol's "Kristall 511" series. I avoid the silver-content solders, as they tend to require much more heat and still look worse. They may be good for mechanic soldering though.

With the right iron temp (ca. 360C), the SN99.3/CU0.7 behaves really nice and predictable in daily production. I don't really miss 60/40 anymore

BTW: I don't like pads smaller than 2.3mm dia (some 91 thou) - I feel they loose grip on the substrate too easily

/Jakob E.

 

[JohnRoberts]

My contract manufacturer used lead free solder on my last run of drum tuners with zero soldering problems.

I have lead free and regular solder on my work bench. The lead free solder joints look different but work adequately.

JR

 

[Matador]

Does anyone find it helpful to use larger pad sizes with lead free solder? I typically use 33mil hole with 80mil pad for 1/4w resistors. Anyone use bigger pads?

Your size is very close to what I use by default (I think I use 40mil hole with 80 mil pad, or a 20 mil annular ring).

I imagine where there's a point of diminishing returns, as the bigger the pad, the more thermal mass (especially to planes), which means less probability that the iron can wet the entire surface of the pad. Plus, tiny annular rings I find lift from the board easier anyways, lead free or leaded alike. I have no proof, but I would guess the best pad size is the one that matches the diameter of the soldering tip you are using, so the entire surface of the tip actually touches the pads surface.

 

[john12ax7]

I'm all in on SN99.3/CU0.7 - e.g from Stannol's "Kristall 511" series.

Thanks, will give that a try. Been using the silver stuff, which also seems to eat tips due to the really high temperature needed.

BTW: I don't like pads smaller than 2.3mm dia (some 91 thou) - I feel they loose grip on the substrate too easily

I have no proof, but I would guess the best pad size is the one that matches the diameter of the soldering tip you are using, so the entire surface of the tip actually touches the pads surface.

Matching tip to pad does seem to be best practice. With 1.6mm and 2.4mm tips common, .080" pads are kind of awkwardly in the middle. Go smaller and the annular ring is too small, so larger would seem the logical step. Better solderability and less delamination issues. Seems like a win win.

 

[pucho812]

I have lead free kester and leaded kester.
Yes the lead free joints do not get shiny but at the end of the day they have never been an issue. Right tools, right temp and you are good to go.

 

[pucho812]

My hako hasn’t let me down in 20 years. Only the occasional tip replacement as needed.

What’s interesting is the number of duplicates on Amazon that are not name brand that work quite well.

I picked one up not long ago that my only complaint is the brightness of the led panel. Super bright. Can use it as a spare light should I need it.

 

[Newmarket]

My contract manufacturer used lead free solder on my last run of drum tuners with zero soldering problems.

I have lead free and regular solder on my work bench. The lead free solder joints look different but work adequately.

JR

Not a problem for professional reflow assembly with appropriate temp / time profile.
Hand work can be trickier. Basically hotter and quicker required.

 

[Newmarket]

Your size is very close to what I use by default (I think I use 40mil hole with 80 mil pad, or a 20 mil annular ring).

I imagine where there's a point of diminishing returns, as the bigger the pad, the more thermal mass (especially to planes), which means less probability that the iron can wet the entire surface of the pad. Plus, tiny annular rings I find lift from the board easier anyways, lead free or leaded alike. I have no proof, but I would guess the best pad size is the one that matches the diameter of the soldering tip you are using, so the entire surface of the tip actually touches the pads surface.

Thermal mass to planes is essentially determined by the number and thickness of the thermal relief spokes. I admit I have a habit of beefing them up to point where desoldering can be awkward