Single and double sided boards

[saturated]

I remember G1 talking about this and it didn't really sink in until now.

I've been practicing removing DIP from cadaver boards.

Last night I was in one helluva dogfight trying to remove some

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I could get most of the stuff off of the bottom but it would still be stuck like chuck i made additional efforts like adding flux and new old kester but no joy. Also I used an iron and tried to bend all the legs to the center of the hole etc 

It was so bad I just had to assume they glued the chip to the board...but they didn't.

Here's a top side shot

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Now in contrast.....I got this IC off in two shakes of a lamb's tail

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But look (and you guys know this of course) there are no pads? on top

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So I was kinda like oh yeah maybe that's what he was talking about 

Pretty ugly but I even tried flowing solder from the top of the board and it didn't help

When I pried with a screwdriver it broke 

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Also I remember chipquick being mentioned I will check it out

 

[saturated]

Another example tried to remove another one

Got a bunch of stuff off of the bottom

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Flip it over....not even loose rocking or anything

Firmly entrenched 

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Tldr

No way Jose 

[Loudthud]

Removing a chip from a double sided board is very difficult as you have discovered. It is not practical to re-use chips that have been removed from a PCB. What many people do is cut the leads where they enter the plastic body of the chip so you can remove them from the board one at a time and not damage the PCB.

What is usually required is a soldering iron that can heat the solder and suck it out of the hole. Such a tool requires maintenance every time you turn it on so it's not practical unless you are removing many chips.

[J M Fahey]

A solder sucker is not enough, it only removes 85-90% of solder, some always remains inside the hole.
Solder wick makes for a far better job.

Absolute best is Chipquick, a low melting point alloy which stays liquid for almost a minute, so you can melt *all* pads at once and pull chip safely with pliers.
Expensive but .....

Pros use hot air desoldering heads, which melt all at the same time.

[tonyharker]

This might be just as good https://www.amazon.co.uk/Low-melt-Solder-Degrees-50g/dp/B08YH9B7SF/ref=sr_1_19?ow+melting+point+solder%2Caps%2C152&sr=8-19

[Jazz P Bass]

A 'double sided' board has a plating from the top of the board, through the component hole & on to the other side.
The hole itself is actually copper plated to connect the circuit paths on the two sides.
The real trick, other than getting the component out, is to not do any damage to the plating.

[galaxiex]

"Plated thru hole" board.

There can be plated thru holes that do NOT join one board side circuit with another on the other board side.

Also don't forget "Vias" that have a plated thru hole but NO component lead.
Usually much smaller (tiny) than a hole for a component.
Their purpose to join one side circuit to the other side.

[g1]

There can be plated thru holes that do NOT join one board side circuit with another on the other board side.

I guess you mean the thru hole does not connect to any traces on one side of the board?

[J M Fahey]

This might be just as good https://www.amazon.co.uk/Low-melt-Solder-Degrees-50g/dp/B08YH9B7SF/ref=sr_1_19?ow+melting+point+solder%2Caps%2C152&sr=8-19

Yes, that.

ChipQuik "should" be the same low temperature melting alloy.

It mixes with original solder:

[galaxiex]

There can be plated thru holes that do NOT join one board side circuit with another on the other board side.

I guess you mean the thru hole does not connect to any traces on one side of the board?

Yes.

[J M Fahey]

Yes.

Plated through holes were invented to join both sides, vias do that too even if no part legs go through them, but some manufacturers (Mesa Boogie for one) use plated through holes even if there is no pad or track at the other side.
Why?

Simply because PTH gets filled with solder and works "almost" like a pin or hollow rivet inserted in the PCB body, giving much higher mechanical strength.

I find it funny when people despise gluing parts in place but trust "soldering" on a PCB.

Surprise surprise, pads and tracks are GLUED    to the board surface by the impregnation varnish , say phenolic or Epoxy.

[Tom Phillips]

Also keep in mind that there are different quality levels of PC boards. The price point of musical instrument amplifiers only allow for a low to mid level PCB quality. The higher quality PCBs are easier to rework but still require good soldering tools and experience for best results.

In my experience, Mesa Boogie actually uses pretty good quality raw PCBs. The Mesa repair nightmares are mostly doe to other reasons.

[Loudthud]

One way I've seen to remove chips from a board is to heat the solder side of the board with a propane torch, then wack the board on a hard surface so the chip flys out before the solder cools. As you can imagine, this damages the board.

A similar way that works on small surface mount parts is to heat up a blob of solder big enough to cover the whole part and pull or pry the part off.

[J M Fahey]

When I was a poor Student teen I used that "burn and slap" method.
Transistors were still kinda expensive (earlier I had even bought OC71 germanium transistors, individually boxed like a tube and more expensive than them) so for experimenting I bought surplus IBM mainframe boards, by the kilo, go figure, and burn/slapped them against a newspaper covered table.


Lots of mystery transistors and switching diodes, alto many .1uF decoupling ceramic capacitors.
The rest was iffy, only a few resistors had useful values.
In any case, everything helps.