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Discussion Starter #1 (Edited)
My son-in-law has me interested in trying a Eurorack module build for him.

The soldering instructions state...

"Your solder joints should have a neat conical shape on BOTH sides of the PCB. If they don’t look the same on both sides then stop! Work out why f and don’t continue until you are getting those results. This isn’t about perfectionism, you are very likely to end up with a destroyed, damaged or defective unit if you’re not hitting that standard."

I also found this in the net...

"I made this illustration to show how a good soldering joint should look on both single sided and double sided PCB’s. The O2 PCB is double sided and hence you need to let the solder run though to the other side. Sometime this isn’t happening and then you can solder the component from the other side instead. Good quality solder will run easier and avoid anything with silver in it, that’s just too hard to use and you’ll get a cold solder joint."




The following is about the best I have ever managed...


Thanks in advance for your comments and advice.

Cheers

Dave
 

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After previously failed attempts, this method seemed to work the best and most consistently for me.
  • Standard rules: Pre-heated/pre-tinned iron, decent solder (I find thinner easier to work with; 60/40 .032"/0.8mm, but that's just preference)
  • I also add flux to the leads (though many people don't)
  • Push the component through the board
  • I usually do a mental 2-2-2 count (straight 6-second count, no breaks)
    • Touch the iron to the lead & pad at the same time (count 2 seconds while heating)
    • Push the solder onto the lead/iron/pad (count 1-2 seconds of pushing; depending on the temperature of the iron and thickness of your solder)
    • Give the solder time to sink into the pad (count 1-2 seconds; depending on the temperature of the iron)
    • Remove the iron by quickly dragging straight up and off the lead
    • DONE!
  • Wait a few seconds for the joint to cool before clipping the leads (or pre-clip them, if that's your thing)
Not saying that's the "right" way, but it works for me. Hope that helps!
 

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To add to the above

- you won't get the perfect symetrical thing as pictured above on double-sided boards most of the time due to the component being in the way (e.g. box film caps). The component side solder gob will always be smaller and this is fine/to be expected. As long as you got the solder to flow through the hole to the pad on the other side it's good.
- clean yer tip, and then instead of tinning it, place the solder against the solder pad/component lead joint area, and put the iron on top of that (touching both as mentioned) - solder sandwich. You want to get just a drop of solder in there and then remove the unmelted solder wire and let the thing heat up. The solder acts as a "heat bridge" to heat up all the parts so they all accept solder. After a few seconds apply more solder - enough to make the joint. Remove the unmelted wire and keep the iron there - you want to see the solder flow down into the through hole. Then done, remove the iron. Basically same as the above, except for the Heat Bridge part, which has changed my life. Same principle applies when desoldering - put a little fresh drop of solder on there (the joint, not the iron - tinning is not as good because you smoke away the flux before you get the iron to the joint) for a heat bridge, and the old gobb will melt (nearly) instantly, vs just a dry or even tinned iron where you can hold the iron there for 10 minutes and nothing.
- use eutectic solder (63/37 Sn-Pb vs 60/40). The benefit here is that this alloy ratio maintains a single melting point, vs 60/40 where the 2 component elements keep their separate melting points and therefore has a 'pasty' lumpy phase which makes it much harder to use (especially desoldering and fine/small work like PCBs). It also does not work as well as a heat bridge due to the pasty phase. Eutectic solder lets you work faster and with less cussing once you get the workflow down. Also yes, thinner solders are better. Ideally a no-clean flux type (or you should wash your PCB off with 99% iso /phosphoric acid afterwards to remove all the flux - I use either with an old toothbrush).
 

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Discussion Starter #4
Thanks for the info and comments.
My soldering skills are reasonably decent.
How to consistently get a "cone" of solder on each side of the pad is the question. Sorry if I was not clear.

- you won't get the perfect symetrical thing as pictured above on double-sided boards most of the time due to the component being in the way (e.g. box film caps). The component side solder gob will always be smaller and this is fine/to be expected.
This is what I thought.
Thanks for the confirmation.
 

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Discussion Starter #5
My son-in-law found this on another forum...

As has been mentioned above soldering one side well should send solder to the other side as well if it is a plated through hole board. However, don't go crazy on checking both sides or do needless rework, sometimes a perfectly fine solder joint won't be visible on the other side, just check continuity and move on.

Agreed. In the old days you might occasionally get a board where the plated through hole didn't bond well with one of the layers, so for higher reliability you made sure the solder flowed out the other end. And even soldered into the vias to make sure they were connected on both sides. But I haven't seen a board like that in decades, so wouldn't worry about it.

Just use it as a way to get feedback on how well you are heating the joint when you solder it, but don't worry about it if there is no solder coming out the other end. It also depends a lot on how well the PCB was designed. If there is a lot of copper that soaks up the heat then you might have to overheat the joint to get solder to really flow out the other side. In that case the extra heat could cause more problems to the part than the lack of solder reaching the other side.

More on this topic here... MUFF WIGGLER :: View topic - Soldering both sides?
 

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Yeah to the immediately above - basically, your drawing fits that category. It's fine. I mean it's best if you at least see it come through, but once you get some confidence in your consistency (you'll see the solder go liquid and sink down into the hole; it's good even if not all the way through to the other side).

I can't stress how much easier/quicker it is with eutectic solder tho. I don't even know why they bother making 60/40 anymore.
 

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Discussion Starter #7 (Edited)
- use eutectic solder (63/37 Sn-Pb vs 60/40).
I will save others having to look up the defn...
eu·tec·tic
yo͞oˈtektik/
CHEMISTRY

adjective
  1. 1.
    relating to or denoting a mixture of substances (in fixed proportions) that melts and solidifies at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them.
This I will certainly keep in mind.
I didn't know that it made such a difference.
 

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The challenge I regularly face is that component leads can become oxidized over time, sitting in the parts bin, making solder flow "obstinate. Jon's recommendation to use flux (and a $10 bottle will likely last a hobbyist their whole life long), is a sound one. To that, I will also add that if your component leads aren't gleaming shiny, take your X-acto knife and just give them a light scraping to take the tarnish off, before applying any flux and soldering.

Is the "ideal" conical shape on both sides essential? Personally, I see it as a nice-to-have rather than a must-have. Certainly if one achieves a double-sided joint of that visible form, that pretty well confirms the quality of the joint and continuity from one side of the board to the other. But its absence does not mean there is NO continuity. Moreover, one really wants to apply as little heat to a board as is possible/reasonable/effective, to protect the integrity of the traces. So if the connection is good, move on to the next joint and leave the last one alone.
 
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