Not knowing the frailty of some circuit boards I have damaged them in the past during dis assembly, (to much heat to release the component) as a rule of thumb are electrolytic and film capacitors able to withstand a fair amount of heat as apposed to the contact points of a board when taking parts in and out numerous times, and how would this apply to the IC Chips as well? and last are there components that just will not tolerate over heating, other than the PSB? This may sound like simplistic questioning, but I have learned a few things in my time some by trial and error, some by asking. Asking is much easier and cheaper, even when embarrassing.
Thanks, Less Opinion
Thanks, Less Opinion
You need a good desoldering tool, here are some inexpensive ones. HAKKO | Desoldering / Rework | Desoldering tool
Down home hands on tricks.
Cut the legs off the op-amp and remove them 1 at a time. (push them through the hole with a tooth pick)
Use solder flux
Use braided solder wick.
Use a round wooden tooth pick to poke in the hole while the solder is still fluid to keep the hole open.
Yes you can do this 1 too many times.
DT
Cut the legs off the op-amp and remove them 1 at a time. (push them through the hole with a tooth pick)
Use solder flux
Use braided solder wick.
Use a round wooden tooth pick to poke in the hole while the solder is still fluid to keep the hole open.
Yes you can do this 1 too many times.
DT
(My instinctive response is to ask why a component needs to be removed and reinstalled several times. I suppose that in a particular design, a specific component may be especially prone to failure and consequently may be replaced several times during repairs. Even this scenario points to a design deficiency that is more properly addressed by modifying the circuit or substituting different components at some point(s) in the circuit rather than repeatedly replacing a component that fails on a regular basis.)
As a general rule of thumb, components - especially passive devices like resistors and capacitors - are orders of magnitude less costly than the printed wiring boards they mount to. Consequently the strategy in repair or rework situations is to avoid damaging the board at all costs, and scrap the component being removed. I think that de-soldering is a much more difficult task than soldering, and it certainly requires a much wider array of tools.
Typically, through-hole components (and many SMD semiconductors) are mechanically removed - using diagonal cutters, a draftsman's knife (Exacto et al), or a fine-pitch jeweler's saw - then the remaining bits of leads and solder are removed using soldering tools.
Physically larger components are generally more tolerant of heat stress than smaller components. I've never seen any serious attempt to salvage and re-use SMD components. As I indicated above, a component which has been subjected to de-soldering is generally assumed to be compromised, if not failed. Any semiconductor device - particularly IC's - are especially susceptible to heat damage. Even if the part doesn't show signs of electrical failure, the desoldering may have reduced it to a kind of "walking wounded" status with an increased probability of failure in the near future under normal usage.
To answer your specific question, resistors, ceramic and mica capacitors, and some inductors are probably the most heat resistant components. Leaded film capacitors are probably next in line - though damage to the internal dielectric film may not be apparent until the re-used capacitor fails prematurely. (By contrast, the SMT versions of film capacitors seem to be especially fragile when soldered or de-soldered.) Electrolytic capacitors are most susceptible to heat damage.
As a general rule of thumb, components - especially passive devices like resistors and capacitors - are orders of magnitude less costly than the printed wiring boards they mount to. Consequently the strategy in repair or rework situations is to avoid damaging the board at all costs, and scrap the component being removed. I think that de-soldering is a much more difficult task than soldering, and it certainly requires a much wider array of tools.
Typically, through-hole components (and many SMD semiconductors) are mechanically removed - using diagonal cutters, a draftsman's knife (Exacto et al), or a fine-pitch jeweler's saw - then the remaining bits of leads and solder are removed using soldering tools.
Physically larger components are generally more tolerant of heat stress than smaller components. I've never seen any serious attempt to salvage and re-use SMD components. As I indicated above, a component which has been subjected to de-soldering is generally assumed to be compromised, if not failed. Any semiconductor device - particularly IC's - are especially susceptible to heat damage. Even if the part doesn't show signs of electrical failure, the desoldering may have reduced it to a kind of "walking wounded" status with an increased probability of failure in the near future under normal usage.
To answer your specific question, resistors, ceramic and mica capacitors, and some inductors are probably the most heat resistant components. Leaded film capacitors are probably next in line - though damage to the internal dielectric film may not be apparent until the re-used capacitor fails prematurely. (By contrast, the SMT versions of film capacitors seem to be especially fragile when soldered or de-soldered.) Electrolytic capacitors are most susceptible to heat damage.
Hi dchisholm, Thank you for the input. This is a learning experience for me as you can most likely tell by the questions. As to why removal and re installment of components, it is a learning experience, a what if I did this instead of that thing. Given a specific repair or by the book build, once in all should be good right? well in a perfect world. I am for the most part new to amp etc. building and my questions are of curiosity in nature as much as anything else. I do have a specific question for you though, are you aware of a online electronics dictionary that is basic form and function, leaving theory aside for a more educated time. Thanks
To de-solder correctly, use plenty of flux and a very hot iron. Speed is the essence. The faster the better to avoid copper track damage or use a de soldering tool. I use a Metcal vacuum de-soldering machine, with assorted tips from 0.2mm to 3mm. The tip is at a constant 380C
This may be of interest to you; soldering - How do I work out what temperature to use when desoldering? - Electrical Engineering Stack Exchange
This may be of interest to you; soldering - How do I work out what temperature to use when desoldering? - Electrical Engineering Stack Exchange
As a general rule capacitors cannot stand too much heat. If you are applying enough heat to damage the board then you may be applying enough heat to damage component too. Desoldering is always harder than soldering.
Semiconductors are more sensitive to heat than caps. Resistors are less sensitive to heat.
If you want to avoid lots of frustration, learn to solder well and quickly.
Semiconductors are more sensitive to heat than caps. Resistors are less sensitive to heat.
If you want to avoid lots of frustration, learn to solder well and quickly.
Not knowing the frailty of some circuit boards I have damaged them in the past during dis assembly, (to much heat to release the component) as a rule of thumb are electrolytic and film capacitors able to withstand a fair amount of heat as apposed to the contact points of a board when taking parts in and out numerous times, and how would this apply to the IC Chips as well? and last are there components that just will not tolerate over heating, other than the PSB? This may sound like simplistic questioning, but I have learned a few things in my time some by trial and error, some by asking. Asking is much easier and cheaper, even when embarrassing.
Thanks, Less Opinion
Proper desoldering technique is generally the same, but the details depend on the nature of the part being removed.
The basic technique is to remove the solder from all the joints holding the part in place, and then undo any mechanical fastenings holding the part in place. Sometimes some heat is needed after that to soften up a thin layer of residual solder that holds the part in place.
The basic tools are:
(1) A proper tip temperature-controlled soldering iron.
(2) A manual or powered solder-sucker which may be based on a specialized soldering iron.
(3) A hot air soldering iron with a tip that lets you melt all the soldered joints that are holding the part in place at the same time for final removal.
For example you may be removing a classic wired-in-place component.
(1) Soften joints one at a time, sucking solder from each one as you go
(2) Remove/unfasten anything that holds the part in place mechanically
(3) As required, quickly melt all residual solder and pull component free
On a through hold PC board.
(1) Soften joints one at a time, sucking solder from each one as you go.
(2) If there are two leads holding it in place you can probably soften any residual solder on them and using a rocking motion, pull the component free.
(3) If there are more than two leads, A hot air soldering iron with a tip (hot air guide) that lets you melt all the soldered joints that are holding the part in place at the same time for final removal.
On a SMT board:
Use hot air soldering iron to melt all soldered joints at once and pull component free using tweezers or vacuum positioning tool.
Since resistors cost a penny, if I remove one, I replace it. I won't solder one back into a circuit, unless I lifted one end for some purpose.
Learn to solder with confidence. One rookie mistake is to solder a joint, then decide maybe it didn't have enough solder, then add more, and after that maybe it doesn't look as shiny as you'd like, so maybe reheat the joint, etc etc etc. And the next thing he knows, he has had a soldering iron on the joint for two minutes and the traces come off the board.
Use enough heat. far better to have a hot tip that heats the joint up quickly, than to use a lower heat requiring the iron stay there longer.
Keep your tips clean and well tinned.
The better your solder work is, the less likely you will damage anything with it.
Many small parts like resistors have almost no wire lead length, the part leads immediately go into holes. But on any part with a quarter inch or more of lead exposed, you can use heat sinks. They do make official heat sink clips for component leads, but alligator clips work too. If I clip a test lead to a resistor lead right by the body, it wicks away the heat as you solder. A hemostat or locking tweezer works too.
Google "solder heat sink" and see many types.
Learn to solder with confidence. One rookie mistake is to solder a joint, then decide maybe it didn't have enough solder, then add more, and after that maybe it doesn't look as shiny as you'd like, so maybe reheat the joint, etc etc etc. And the next thing he knows, he has had a soldering iron on the joint for two minutes and the traces come off the board.
Use enough heat. far better to have a hot tip that heats the joint up quickly, than to use a lower heat requiring the iron stay there longer.
Keep your tips clean and well tinned.
The better your solder work is, the less likely you will damage anything with it.
Many small parts like resistors have almost no wire lead length, the part leads immediately go into holes. But on any part with a quarter inch or more of lead exposed, you can use heat sinks. They do make official heat sink clips for component leads, but alligator clips work too. If I clip a test lead to a resistor lead right by the body, it wicks away the heat as you solder. A hemostat or locking tweezer works too.
Google "solder heat sink" and see many types.
If I want to remove a resistor to check it I actually cut the lead about 2mm from body and lift it up.
Then to put back I lower the leg and solder the resistor back together.
I remove IC's by chopping legs high up next to IC body.
I then heat a pin first then quickly pull it out with long nosed pliers.
I have to admit I was a failure at soldering in SMD IC's, I kept blowing them up with too much heat, so I stick to through hole now.
I use a hot air heat gun to remove SMD.
Then to put back I lower the leg and solder the resistor back together.
I remove IC's by chopping legs high up next to IC body.
I then heat a pin first then quickly pull it out with long nosed pliers.
I have to admit I was a failure at soldering in SMD IC's, I kept blowing them up with too much heat, so I stick to through hole now.
I use a hot air heat gun to remove SMD.
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