How does this affect lifespan, especially surface mounted solder joints? I suspect it does increase it, as automotive devices as often potted, but how much? Can it be predicted roughly? Does potting help increase the lifespan of solder joints?
Judging by potted Altec XOs from the '40s, I'd say indefinitely, though guess it depends on the potting compound. Altec's appeared to be basically a thicker version of the same honey/gold tinted goop that ~encased the transformers/windings destined for the tropics, ships, etc..
edit: Wasn't paying close enough attention, no experience with Polyurethane
edit: Wasn't paying close enough attention, no experience with Polyurethane
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Most vehicle pcboards have a conformal coating. Looks like polyurethane.
This coating stops/reduces any ingress of moisture.
Potting is to place the pcb in a box and fill it with potting compound, this is normally epoxy based and renders the item, 'no longer serviceable' but vibration and moisture resistant.
This coating stops/reduces any ingress of moisture.
Potting is to place the pcb in a box and fill it with potting compound, this is normally epoxy based and renders the item, 'no longer serviceable' but vibration and moisture resistant.
<<Potting is to place the pcb in a box and fill it with potting compound, this is normally epoxy based and renders the item, 'no longer serviceable' but vibration and moisture resistant.>>
Full encapsulation is also used for design security. I have not observed any operational life time changes with my potting but note that most if not all potting compounds are excellent thermal insulators and will shorten the life of heat producing components.
But the most important issue is selecting the appropriate compound. Some have an acid cure (gives off ascetic and other acids when cure chemicals are added or when exposed to air) which will rapidly eat solder and copper. Must make sure you select a neutral cure. I speak from embarrassing professional experience.
Spray on conformal coatings (that are designed for PCB use) are used to protect the PCB from moisture and dust etc and minimise leakage currents. They do therefore extend the operational life.
Full encapsulation is also used for design security. I have not observed any operational life time changes with my potting but note that most if not all potting compounds are excellent thermal insulators and will shorten the life of heat producing components.
But the most important issue is selecting the appropriate compound. Some have an acid cure (gives off ascetic and other acids when cure chemicals are added or when exposed to air) which will rapidly eat solder and copper. Must make sure you select a neutral cure. I speak from embarrassing professional experience.
Spray on conformal coatings (that are designed for PCB use) are used to protect the PCB from moisture and dust etc and minimise leakage currents. They do therefore extend the operational life.
Thank you for adding these points to the topic of discussion. I'm using a specialized potting compound for electronics, Sepur 116 by Demak, which I previously tested with transformers and it has a filler somewhat with good heat transfer capabilities. It is rated with a thermal conductivity of Thermal conductivity of 0,65 W/M.K
https://www.demakgroup.com/resins/
The circuits I think of potting are modern low power consumption DAC converters, which should not have highly heating parts, including the local regulators. Yes, the idea behind the potting is mostly design security, but if it extends life, it can be taken as a bonus.
What about the electrolytic capacitors? I believe one should design the PCB with long lasting capacitors in the first place.
https://www.demakgroup.com/resins/
The circuits I think of potting are modern low power consumption DAC converters, which should not have highly heating parts, including the local regulators. Yes, the idea behind the potting is mostly design security, but if it extends life, it can be taken as a bonus.
What about the electrolytic capacitors? I believe one should design the PCB with long lasting capacitors in the first place.
Acetic acid liberation during cure is a feature of moistured cured acetoxy silicone systems, as used in bathroom sealants, not electrical potting compounds.
Poyurethane based systems do not liberate acids, but can be more hazardous to handle, particularly the clear, colourless, and non-yellowing, types - be sure to read the safety instructions carefully, esp. any references to breathing protection.
Poyurethane based systems do not liberate acids, but can be more hazardous to handle, particularly the clear, colourless, and non-yellowing, types - be sure to read the safety instructions carefully, esp. any references to breathing protection.
There are hundreds if not thousands of compounds used. Each with its own pros and cons. But what I use is a special epoxy made my Araldite. CY106
My application is high voltage. So I need the best dielectric epoxy I could find.
It for sure protects my automotive circuits. Even after 20 years there is zero oxidisation or changes to any solder or component.
I did try various conformal coatings. But they all seemed to conduct some voltage. Esp high voltage.
For more info chk this link.
https://www.generaladhesivos.com/proveedor-pegamento/885hoja-tecnica-AW 106-HV 953 U.pdf
My application is high voltage. So I need the best dielectric epoxy I could find.
It for sure protects my automotive circuits. Even after 20 years there is zero oxidisation or changes to any solder or component.
I did try various conformal coatings. But they all seemed to conduct some voltage. Esp high voltage.
For more info chk this link.
https://www.generaladhesivos.com/proveedor-pegamento/885hoja-tecnica-AW 106-HV 953 U.pdf