I've been doing a lot of PCB boards lately and I've found that the over-use of through holes can make some parts unsolderable. Namely parts that have many pins and don't give any access to the top side of the board, terminal blocks, relays, some tube sockets, etc. I've found that through holes make it real easy to do routing, but for parts that have many pins Its better to use one-sided bottom pads wherever possible. When you solder a through pad some of the solder "mushrooms out" on the opposite side under the part that has many pins and is tight against the board. So removing such a part later is nearly impossible even with a solder sucking iron, you cant wick that mushroom cap under the part either. And the solder sucker doesn't suck out the mushroom cap on the other side, so the pins are basically trapped. Adding to the unsolderability is that you can't pull one pin at a time, you'd need to melt all the pins and pull the whole part, try doing that with a 8 pin relay. Now this problem doesn't happen with unsoldering two leaded parts, you just melt and yank, easy, then clean the pads and install the new part.
I'm having to revise some of my boards to limit the use of thru pads under multi-pinned parts that hug the board, to keep them repairable in the future.
Just thought I'd pass along this observation.
I'm having to revise some of my boards to limit the use of thru pads under multi-pinned parts that hug the board, to keep them repairable in the future.
Just thought I'd pass along this observation.
yes was a pain with Lead (Pb) and Tin (Sn) soldering but with hot hair gun flux brahama help was possible unsolder multipin stuff
but wit green no lead sodering become quick a nightmare
but wit green no lead sodering become quick a nightmare
I've greatly improved my %successfulRepairs by doing 3 things:
Now the desoldering tool clears out everything, even topside "blobs", and the desoldered component falls out due to gravity alone.
1. Purchasing a Hakko FR-301 desoldering tool with electric vacuum pump
2. Enlarging all drill holes and annular rings in my PCB footprint library, so component leads don't fill up the hole and molten solder can freely flow to the vacuum nozzle
3. Quit bending component leads; leave them straight and perpendicular to the plane of the PCB
2. Enlarging all drill holes and annular rings in my PCB footprint library, so component leads don't fill up the hole and molten solder can freely flow to the vacuum nozzle
3. Quit bending component leads; leave them straight and perpendicular to the plane of the PCB
Now the desoldering tool clears out everything, even topside "blobs", and the desoldered component falls out due to gravity alone.
Yes, if you make the hole diameter about 20% larger than the lead diameter,
then soldering and desoldering will both work better.
then soldering and desoldering will both work better.
There are various methods unsoldering components. You can wrap a wire around the legs as a heat spreader. Add flux and lots of fresh solder and what makes it even easier is to use ChipQuik SMD removal solder with very low melting point 58°C (136°F). Then heat up with high power solder iron or a hot air gun. After the component is removed, you can remove the solder with solder sucker or flux and solder wick.
Welcome to the wonderful world of Board-Level Repairs!
I've spent 45+ years servicing video and audio products, along with other equipment, and indeed at times it's not much fun, even with all the right tools.
I suppose "air roasting" the whole relay or terminal block at once to the melting point is an option, but it may fry other parts. No access to the topside, multiple pins (not leads), and through holes is going to be a difficult repair.
Another option is to totally destroy the relay or terminal block with a pair of vice grips, crack it up, to get it to the point where the only thing that remains are the pins. But you may not have clearance on the sides to crack up the bakelite relay or terminal block. Judicious use of through holes under multi-pin / close-up parts really helps out the repair man, often you can avoid a through hole on the multi-pin part by just dropping a unused through hole along the trace outside the part to get the top-to-bottom connection. IOW I'm not going to put through holes on such parts unless its absolutely necessary and then only for one or two pins.
Another option is to totally destroy the relay or terminal block with a pair of vice grips, crack it up, to get it to the point where the only thing that remains are the pins. But you may not have clearance on the sides to crack up the bakelite relay or terminal block. Judicious use of through holes under multi-pin / close-up parts really helps out the repair man, often you can avoid a through hole on the multi-pin part by just dropping a unused through hole along the trace outside the part to get the top-to-bottom connection. IOW I'm not going to put through holes on such parts unless its absolutely necessary and then only for one or two pins.
Last edited:
Yup, I've done all three of those. Then I wanted to remove an Omron relay soldered into thru holes and found it impossible. It simply wont suck out the topside solder and heating all 8 pins to melting at once is impossible. They are not in a row so even my wide one inch chisel tip for unsoldering DIP's can only melt 4 at a time.
You can try wrapping a wire around them. Here is the idea shown (random video): Easy Multi Pin Through Hole Socket removal with just a soldering iron Using this Trick - YouTube
Oh boy that is crazy sick! Thanks, would have never thought of this trick. He specifically mentions they are through holes too.
Pretty crude, the solder splashes all over, and the board and pads are way overheated.
No pro would do this. One successfully reworked pcb pays for a real desoldering tool.
No pro would do this. One successfully reworked pcb pays for a real desoldering tool.
I have all the usual tools, but sometimes it doesn't work, for various reasons: too many, too thick layers, the large component to be desoldered makes an airtight contact with the PCB surface, preventing air from being sucked, etc.
In such cases, I often make an improvised tool from copper sheet (1mm or so).
It is soft, easy to cut with a shear, easy to form, stamp or punch with the tools of a small, basic mechanical workshop, and once adapted to the right shape, it is easy to tin and with a good thermostat-controlled iron, you can heat and melt one or two dozens of solders simultaneously, gently, and in a very localized way.
Tomorrow, I'll post some example pictures.
Some are used only once, but most can be used on different patterns.
Once all the solder points are melted, the component falls almost by itself, like a ripe fruit.
Bent pins are a nightmare though
In such cases, I often make an improvised tool from copper sheet (1mm or so).
It is soft, easy to cut with a shear, easy to form, stamp or punch with the tools of a small, basic mechanical workshop, and once adapted to the right shape, it is easy to tin and with a good thermostat-controlled iron, you can heat and melt one or two dozens of solders simultaneously, gently, and in a very localized way.
Tomorrow, I'll post some example pictures.
Some are used only once, but most can be used on different patterns.
Once all the solder points are melted, the component falls almost by itself, like a ripe fruit.
Bent pins are a nightmare though
Good idea to melt all the pins at once on parts where the pins might not be arranged all in a row (like relays). I have a bunch of copper plate that would work. What this guy did in the video is just way too much heat for me, he didnt need to cook it that much.
If the part is good and I don't care about the PCB all bets are off. I've used a propane torch to heat parts out of a board before. I've also used a toaster oven to "reflow" a video card - it actually worked BTW.
I have several strategies depending on the part and problem though.
In the case of the relay is bad and I want to change it, I'd probably break it to the point of individual pins like Windcrest.
I know I wanted to just retouch a relay board that I build and soldered a little crooked. 14 pin relay and no way for me to heat all pins except oven which would melt the relay too. So I lived with it.
For anything else I use wick.
I've also just cut out the part and attached the new one to the old ones lead stubs.
Making your boards with slightly bigger holes is a good idea, too.
I have several strategies depending on the part and problem though.
In the case of the relay is bad and I want to change it, I'd probably break it to the point of individual pins like Windcrest.
I know I wanted to just retouch a relay board that I build and soldered a little crooked. 14 pin relay and no way for me to heat all pins except oven which would melt the relay too. So I lived with it.
For anything else I use wick.
I've also just cut out the part and attached the new one to the old ones lead stubs.
Making your boards with slightly bigger holes is a good idea, too.
Loved it.
And it certainly won´t overheat board more than any hot air solution!!!!
Hot air is a turbulent hot gas and will heat **everything** around; while this method heats basically metallic solder only,by conduction, so only what we are interested in.
Good solution.
Here they are:
On the left, various examples made from copper sheet or tubing.
On the right, a spring-loaded gripping tool for DIP, through-hole IC's: before the heating, you install it on the components side, and it exerts a permanent traction on the component.
As soon as the last solder is melted, the component is extracted automatically.
On the top is a stripped coaxial cable having a silver-plated braid.
When it is freshly stripped, the braid acts as a "tin magnet", more effective than conventional solder wick, because of the affinity of tin for silver.
A drop or two of flux, and you can remove the tiniest remains of solder
Attachments
Congratulations, excellent ideas.
There are some off the shelf similar tips, but only in the most popular patterns, such as DIP16, etc.
Custom making rules!!!!
(Some call that DIY,go figure 😉 )
There are some off the shelf similar tips, but only in the most popular patterns, such as DIP16, etc.
Custom making rules!!!!
(Some call that DIY,go figure 😉 )
Great idea making custom footprint de-soldering tools. I use the Omron G2R series of relays a lot, I should make one for that footprint. Omron sells more G2R series relays than all their other products combined, so it would be useful. This is the relay I was trying to remove from through holes that started this whole thread!
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g2r.pdf
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g2r.pdf
With round pin components you can use hollow stainless steel tubes one pin at a time. (Assuming you have enough space around the pin.) You heat up the solder and push the hollow stainless steel tube over the pin between the pin and the pcb via hole. Then you let the solder cool. Next "gently" twist out the stainless tube. Then continue with the next pin.
The solder does not stick/wet to the stainless steel.
That obviously does not work with flat terminals. Only round and small square pins.
The solder does not stick/wet to the stainless steel.
That obviously does not work with flat terminals. Only round and small square pins.