Hello Everyone,

I've uploaded a YOUTUBE video showcasing my soldering practice on a board and I'd love to get your insights:

• How would you rate my technique?
• Have I made any noticeable beginner mistakes?
• Can you offer any tips to refine my soldering approach?
• Given the video, do you think I'm ready to take on real FCs and ESCs on FPV drones?

Additionally, I observed a strange spill or residue on the board after soldering. I've been using a no-clean flux pen, so I'm wondering:

• Could the residue be from the flux pen or perhaps from the solder's flux (By the way, the solder i used is a 60 40 Sn/Pb and it got 2 % flux) ?
• Is such a residue common?
• I attempted cleaning with isopropyl alcohol, yet some shiny areas remain, appearing like leftover residue. Any thoughts on this?

Your feedback would be greatly appreciated.

Thanks in advance.

 

Difficult to say, as you have not actually soldered anything, you have just tinned the board.
I would recommend:
Get a 2.4mm "screwdriver" tip - it transfers more heat evenly to the board. Pointed tips damage tracks.
Read @Ya’akov 's blog
https://forum.allaboutcircuits.com/ubs/1-what-is-soldering.1807/
https://forum.allaboutcircuits.com/threads/new-blog-a-neophytes-guide-to-hand-soldering.191451/

 

Great, but you are not actually making any connections, try soldering some SMD resistors on those pads next.
Get some paste flux, drown that thing in flux, it's almost impossible to use too much, easy to use too little.

Watch some laptop repair videos, you'll see how much flux the pros use when working on those insanely tiny parts.

 

Difficult to say, as you have not actually soldered anything, you have just tinned the board.
I would recommend:
Get a 2.4mm "screwdriver" tip - it transfers more heat evenly to the board. Pointed tips damage tracks.
Read @Ya’akov 's blog
https://forum.allaboutcircuits.com/ubs/1-what-is-soldering.1807/
https://forum.allaboutcircuits.com/threads/new-blog-a-neophytes-guide-to-hand-soldering.191451/

Thank you @Ian0, for your insights and for sharing the resources. I'll check Ya’akov's blog.
Regarding the 2.4mm "screwdriver" tip, isn't that diameter a bit large for soldering smaller surfaces, especially those on the edges of the board?

 

Great, but you are not actually making any connections, try soldering some SMD resistors on those pads next.
Get some paste flux, drown that thing in flux, it's almost impossible to use too much, easy to use too little.

Watch some laptop repair videos, you'll see how much flux the pros use when working on those insanely tiny parts.

Thank you for the advice, @Sensacell. I appreciate the suggestion about practicing with SMD resistors. Regarding the flux, when you mention "paste flux", are you implying that it's better to use a flux syringe for precision instead of a flux pen, especially when dealing with those tiny parts?

 

Thank you @Ian0, for your insights and for sharing the resources. I'll check Ya’akov's blog.
Regarding the 2.4mm "screwdriver" tip, isn't that diameter a bit large for soldering smaller surfaces, especially those on the edges of the board?

I solder LQFPs with 0.5mm pin spacing using a 3.2mm bit. The flux will prevent the solder from bridging two pins. Use the iron to move the solder along the row of pins until it reaches the end (tilting it will let gravity help the process) then remove he excess with a desoldering pump or braid.

 

What type of flux does your solder have. Some types like "water washable" MUST be removed as they are very corrosive. I have found them very irritating to my throat and eyes as well.

 

What type of flux does your solder have. Some types like "water washable" MUST be removed as they are very corrosive. I have found them very irritating to my throat and eyes as well.

I use this one Electric Soldering Iron 60/40 100g 0.8mm Tin Fine Wire Core 2% Flux Welding Solder Wire with Rosin and Low Melting Point
No further details about the flux other than the title"s description.

 

How would you rate my technique?

You haven't soldered anything. Good technique is required to form joints between components and pads.

If you're going to use 60/40, you don't want the board to be able to move around before the solder solidifies.

Have I made any noticeable beginner mistakes?

There isn't enough magnification to see if you're actually tinning the pads or just applying blobs of solder. Blobs as in too much solder. A good joint would have a concave profile. Yours are all convex.

Can you offer any tips to refine my soldering approach?

You won't be able to tell if you're soldering unless you actually try to make joints between components and the pads.

Could the residue be from the flux pen or perhaps from the solder's flux (By the way, the solder i used is a 60 40 Sn/Pb and it got 2 % flux) ?

Is such a residue common?

All flux will leave a residue, even no-clean.

I attempted cleaning with isopropyl alcohol, yet some shiny areas remain, appearing like leftover residue. Any thoughts on this?

What is the water content of the isopropyl alcohol? If you're not submersing the board in it, you might need to start with 70% so it doesn't evaporate so fast and finish with 99%. It could take several passes to remove the residue. The longer it sits, the harder it'll be to remove.

 

You haven't soldered anything. Good technique is required to form joints between components and pads.

If you're going to use 60/40, you don't want the board to be able to move around before the solder solidifies.
There isn't enough magnification to see if you're actually tinning the pads or just applying blobs of solder. Blobs as in too much solder. A good joint would have a concave profile. Yours are all convex.
You won't be able to tell if you're soldering unless you actually try to make joints between components and the pads.
All flux will leave a residue, even no-clean.
What is the water content of the isopropyl alcohol? If you're not submersing the board in it, you might need to start with 70% so it doesn't evaporate so fast and finish with 99%. It could take several passes to remove the residue. The longer it sits, the harder it'll be to remove.

Thank you for the insightful feedback; it precisely highlights where I need to improve.

Regarding the isopropyl alcohol, I've been using a 99.99% concentration, so it contains just 0.001% water.

 

Regarding the isopropyl alcohol, I've been using a 99.99% concentration, so it contains just 0.001% water.

Are you using a short bristle brush to scrub the residue? Are you submerging the board?

I've found that 90%+ isopropyl alcohol evaporates too fast if you're brushing it on. I use 70% for the first pass then switch to 90%+ for final cleanup (if needed). For really stubborn cases, I use a commercial flux remover.

For brushing, I use horsehair acid brushes with the bristles cut to various lengths. For really stubborn flux, I cut bristles down to 1/32".


Isopropyl alcohol absorbs water, so your 99.99% won't stay that way.

 

Are you using a short bristle brush to scrub the residue? Are you submerging the board?

I've found that 90%+ isopropyl alcohol evaporates too fast if you're brushing it on. I use 70% for the first pass then switch to 90%+ for final cleanup (if needed). For really stubborn cases, I use a commercial flux remover.

For brushing, I use horsehair acid brushes with the bristles cut to various lengths. For really stubborn flux, I cut bristles down to 1/32".
View attachment 300065

Isopropyl alcohol absorbs water, so your 99.99% won't stay that way.

Thank you for your tips again.

I opted for a Qtip over a brush, but I've noticed it leaves white fibers on the board and doesn't seem very effective. I'm considering purchasing a brush for better results.

 

I opted for a Qtip over a brush, but I've noticed it leaves white fibers on the board and doesn't seem very effective.

For final cleanup, I use low lint Kimwipes (EX-L). 4.5"x8.5" rolled up with heat shrink around it for stiffness. I cut away the heat shrink from one end to expose some of the tissue and use it to wipe residue from the board.

 

Seeing all the smoke made with your soldering, I Knew your welding solder was cheeep Chinese junk from AliExpress.
I use North American Name Brand 63/37 solder with a flux core with a Temperature-Controlled Weller soldering station.
The temperature control and good quality flux guarantees that the flux does its job of cleaning properly without being incinerated into smoke.

 

Unknown solder from AliExpress is not your friend – I had some solder from one of the Chinese sources that was beyond crap. An inch or two would melt as expected at normal soldering temperature, then there would be a section that wouldn't melt even if I cranked up the iron temperature. I'm not sure how that can even happen other than the tin/lead alloy being inconsistent.

Get a quality name brand solder. The frustration you save will be worth it. Kester 44, 63/37 with a rosin core is my go-to solder. Not cheap but a spool will last a long time.

 

I only use Q-tips for spot cleaning after rework. When I do a whole board, I soak, scrub, blow the dirty alcohol off with compressed air, do the same with the brush, then apply some fresh isopropanol on the brush and blow that off, then apply fresh alcohol to the board and scrub some more to rinse it, and then blow it off again. It's good to have the isopropanol in a spray bottle for this.

 

Q-tips and an old tooth brush with Isopropyl alcohol works well for me. On smaller boards I often submerge the board in alcohol or use a spray bottle and saturate the PCB.