EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: tangelo on July 16, 2019, 01:49:19 am
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Hello community.
I did a few simple DIY kits at school when I was ~10 years old. Now 28+ years later I wanted to try this again (due to wanting to be able to fix some basic electronic stuff and not just throw it away).
Here is my first attempt. Any comments & criticisms about the solders joints is highly welcome.
Did I make any glaring mistakes? What aspect should I focus on honing more/next?
I used a T12 clone with D16 tip and a 63/37 0.8mm solder.
Cheers
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You’re gonna have to post some much better photos to get any kind of detailed critique, since the joints aren’t in focus and so there’s no way to evaluate them. The only thing I can see is that many of the small pads have too much solder — it should never be bulging. (The ideal shape is slightly concave.) A finer solder might help with those smaller pads.
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Looks fine to me and I have been soldering for 40 years !
I like to see plenty of solder on joints and not just a thin covering.
The biggest challenge these days is fine scale SMD components.
I recently had to try to hand solder a 64 pin TQFP PIC micro on 0.5mm pitch !
I found the trick in the end was blob loads of solder on all 4 sides with plenty of flux.
Then apply more flux and remove excess solder with copper braid.
I had added rows of via's next to the PIC so I could buzz out for shorts.
In about 5 pcb's I just failed on one where I had pushed too hard with the soldering iron and bent a couple of pins.
I couldn't straighten so it had to go in the bin. I just put it down to the cost of learning.
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Looks OK. As for tooki's comment about amount of solder, I agree you could use maybe 10-20% less solder, but it isn't too excessive to cause any problem.
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Thanks for the feedback guys.
I did a few more DIY-kits and used thinner solder and concentrated on using less of it and the results do look better and more of that "slightly concave"
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I recently had to try to hand solder a 64 pin TQFP PIC micro on 0.5mm pitch !
I've just (last week!) discovered drag soldering for those fine pitch parts. I was amazed how quick and easy it was. I've not done a big chip yet, but about a dozen tssop 0.65mm 28 pin parts without a single failure. I bought a gullwing tip for my Weller and a bottle of liquid RMA flux, and watched a few youtube videos that made it look ridiculously easy. It actually was.
I've been doing down to 0.5mm the hard way for years (like yours, or using a 0.1mm tip and doing a pin at a time under the microscope) but never again. Drag soldering for me!
Cleaning that flux off is a sticky pain though.
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I did a few more DIY-kits and used thinner solder and concentrated on using less of it and the results do look better and more of that "slightly concave"
The reason for the concave filets is that a bad joint that is overfilled might look kinda sorta like a good one. But if you have a good enough view of what you're doing/seeing as you do it (with good lighting and magnification if necessary, this is pretty moot, IME. You can watch how the joint fills and know it's fine, then overfill it all you want, no problem.
It you are making one single joint out of the blue and can't see what you're doing until after you set your iron down and take a macro picture, then yeah, you might accidentally mistake an overfilled bad joint for a good one.
Or when you are going along and one joint takes longer before it wets out, this could be due to thermal coupling to a plane or a large component... this is where you have to take more notice of not accidentally making a cold joint.
It's basically a rule for your workers. Do as I say, not as I do, because I don't trust any of you monkeys. So if you are applying for a job as a production solderer, then yeah, be a good boy and practice your concave filets.
That said, when you do let a cold joint get by, it can waste quite a bit of your time to debug, and it might not be today. It might be 3-4 years later when it causes a problem.
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KL27x has it spot on. To rephrase:
For successful joint, all of the following needs to be true at the same time:
Part A = PCB track
Part B = component leg
1) Part A must be clean and not too badly oxidized,
2) Ditto for Part B
3) Part A must heat up to the soldering temperature,
4) Ditto for Part B
Applying heat equally requires a bit of exercise. For example, when soldering a small component leg to a large copper plane, you keep the iron tip 90% at the plane, and 10% at the component leg. Or vice versa.
Now a typical mistake is that you mostly heat up only the component leg, and the iron tip doesn't touch the PCB track properly. Now the solder forms a ball to the component leg, which doesn't properly connect to the PCB. If you apply only a modest amount of solder, this ball is small and it's obvious it won't connect - especially if you visually compare it to the mental reference image of proper "concave" shape.
But if you apply a lot of solder, you create a large ball, which hides the PCB track under it. It looks quite similar to a successful joint with excess solder, but it looks different to a successful joint with modest amount of solder!