PCBs with solder pads on both sides - VS - one side

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PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Thu May 17, 2018 1:52 pm

Hi brainstrust :)

I have been working on a DIY project with 3 PCBs...
2 of these have solder pads on the back (green side of PCB)
and the power regulator PCB has solder pads on both sides

Now, greanted i'm a beginner, but i dont think i'm that terrible at soldering...
i'm using a 40W solder station from jaycar, not amazing but i figure it does the job like this one:
https://www.jaycar.com.au/40w-temperature-controlled-soldering-station/p/TS1620

When i solder the single pad PCBs...my wetting angle on my joins is woeful...
even when applying flux from a fluxpen. I've even tried lowering heat on the iron to see what difference it makes, and all that happens is my iron just sticks to parts or the solder pad rather than melt solder.

When i do the same technique on the double solder pad...wow...the difference is light and day...
my joins are perfect and solder flows through to the front of the PCB making an awesome connection.

How concerned should I be about wetting angle in general, and my circuits working as designed??
I guess if i test the project and it works as it should I'm guessing its OK...
but i moreso would like to know of others experience
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Re: PCBs with solder pads on both sides - VS - one side

Postby Gian » Thu May 17, 2018 2:39 pm

I find that lead free solder is harder to work with.
And have gone back to lead(ed) solder
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Re: PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Thu May 17, 2018 2:49 pm

yes so i've heard, i'm 90 percent sure i am using leaded though...i sure bloody hope.
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Re: PCBs with solder pads on both sides - VS - one side

Postby stosostu » Fri May 18, 2018 1:39 pm

The secret to good solder flow is the cleanliness of the pad and lead(s). Immediately prior to applying solder or inserting the component, clean the pad. The best thing for this is the old rubber INK type eraser that has some abrasive ingredient, but they're hard to find these days, so you can use a fine emery board, like the ones used for filing finger nails. Finally, wipe with a pad with isopropyl alcohol. Do the same with the component leads and insert the component. Apply a little liquid flux to the pad and lead(s), apply a little solder to the iron tip, put the iron tip at 45 degrees to the pad with the tip at the spot where the lead meets the pad to bring both the pad and the lead up to the melting temperature of the solder (this usually takes only 1 or 2 seconds), then apply a small amount of solder to the joint, close to the iron tip. Allow the solder to run around the pad and then remove the solder and the heat. The temperature setting is critical and must be enough to do the job without overheating the PCB area, especially with fibreglass boards, unfortunately, this only comes with practice, but you'll soon get the idea.

If you really want to get to a high standard of soldering I recommend the NASA Soldering Standard, which we were taught at the RAAF School of Radio, back in the 70s.

https://nepp.nasa.gov/docuploads/06AA01 ... 8739.3.pdf
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Re: PCBs with solder pads on both sides - VS - one side

Postby Wiz » Fri May 18, 2018 6:31 pm

stosostu wrote:The secret to good solder flow is the cleanliness of the pad and lead(s). Immediately prior to applying solder or inserting the component, clean the pad. The best thing for this is the old rubber INK type eraser that has some abrasive ingredient, but they're hard to find these days, so you can use a fine emery board, like the ones used for filing finger nails. Finally, wipe with a pad with isopropyl alcohol. Do the same with the component leads and insert the component. Apply a little liquid flux to the pad and lead(s), apply a little solder to the iron tip, put the iron tip at 45 degrees to the pad with the tip at the spot where the lead meets the pad to bring both the pad and the lead up to the melting temperature of the solder (this usually takes only 1 or 2 seconds), then apply a small amount of solder to the joint, close to the iron tip. Allow the solder to run around the pad and then remove the solder and the heat. The temperature setting is critical and must be enough to do the job without overheating the PCB area, especially with fibreglass boards, unfortunately, this only comes with practice, but you'll soon get the idea.

If you really want to get to a high standard of soldering I recommend the NASA Soldering Standard, which we were taught at the RAAF School of Radio, back in the 70s.

https://nepp.nasa.gov/docuploads/06AA01 ... 8739.3.pdf



I did that in the 80s at Wagga... :)
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Re: PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Fri May 18, 2018 6:42 pm

dont know what happened to my post!
Thanks so much for the detailed reply Pete :)

Ive seen that nasa doc in passing before, i guess i should look at it again

I didnt know if people cleaning resistors with alcohol an rubbing solder pads was being "ocd" or overkill...
i guess i dont really care if it avoids crappy joins!
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Re: PCBs with solder pads on both sides - VS - one side

Postby stosostu » Fri May 18, 2018 7:28 pm

I did that in the 80s at Wagga...


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Re: PCBs with solder pads on both sides - VS - one side

Postby stosostu » Fri May 18, 2018 7:37 pm

Jamil,
I didnt know if people cleaning resistors with alcohol an rubbing solder pads was being "ocd" or overkill...
i guess i dont really care if it avoids crappy joins!


The copper pads and tracks on PCBs will become oxidized, and even the tinned leads on components become contaminated, quite quickly and this is the main reason for poor solder joints. The worst thing is a joint that looks reasonable but contains contaminants, because it may work fine initially, but over time become intermittent or fail. Then you have the whole fault finding job to undertake to fix it. In my experience, a lot of faults in older amplifiers and audio electronics come from poor soldering, to the stage that, if I have a PCB that is intermittent, I will reflow every joint, it's quicker and easier than fault finding and fixes intermittent faults 90% of the time.
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Re: PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Sun May 20, 2018 5:47 pm

just to go back to a previous comment you made about the pads.
would going at each pad with a bit of suuuuper fine grit sandpaper be OK?
the idea of scratching away at a PCB wth emery board scares me a little

also, i sw somewhere online a millitary electronic circuit book i downloaded :)
its no RAAF but im sure it's no nonsense!
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Re: PCBs with solder pads on both sides - VS - one side

Postby stosostu » Mon May 21, 2018 10:01 am

Super fine sandpaper would be OK, but emery board has a softer abrasive as it is intended for use on finger nails which are softer than wood or metal. If you can find an ink eraser, they are by far the best.
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Re: PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Mon May 21, 2018 1:13 pm

great! I'm sure i can find something on ebay :)
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Re: PCBs with solder pads on both sides - VS - one side

Postby rob » Mon May 21, 2018 9:49 pm

clean the pcb with 1200 grit emery paper ( hardware store ) wetted with isopropyl alcohol, the clean off with a chux wetted with iso.
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Re: PCBs with solder pads on both sides - VS - one side

Postby jkhuri44 » Wed May 23, 2018 11:26 am

thanks for chiming in Rob!
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