A friend offered me a PCM2704 USB DAC board and I thought of potting the board into a nice enclosure. I shared the idea of potting, however he warned me that some ICs as this one could be sensitive from leftover solder rosin flux increasing the capacitance between high frequency traces, probably bringing malfunction to the circuit operation. Now, a potting compound would do the same, with a dielectric constant of at least 3.
What do you think?
What do you think?
Chips on your DAC board need to dissipate heat no matter how small the amount. If you fully cover them with potting compound they are likely to fail in a short time.
What advantage did you think potting would provide?
What advantage did you think potting would provide?
Is this used for military and industrial to protect components from excessive vibration? In these cases the equipment is disposable and replaceable.
Ages ago a DAC was being sold online for hundreds of dollars when it was actually cheap $50 Chinese PCM1798 board. The seller tried to hide the identity of the DAC but people who owned and bought the Chinese original spotted it and called them out. Very shady.
A company I worked for made and assembled PCBs for fire alarms to be used in wet/damp conditions and we vacuum shrink wrapped the boards in a mylar covering, it could be removed easily enough after being in an oven. Think we stopped doing it to reduce assembly costs and it was unnecessary once the enclosure had been uprated to IP68 or whatever.
Do not use potting compound.
Ages ago a DAC was being sold online for hundreds of dollars when it was actually cheap $50 Chinese PCM1798 board. The seller tried to hide the identity of the DAC but people who owned and bought the Chinese original spotted it and called them out. Very shady.
A company I worked for made and assembled PCBs for fire alarms to be used in wet/damp conditions and we vacuum shrink wrapped the boards in a mylar covering, it could be removed easily enough after being in an oven. Think we stopped doing it to reduce assembly costs and it was unnecessary once the enclosure had been uprated to IP68 or whatever.
Do not use potting compound.
If you're concerned about corrosion, clean the board thoroughly of flux and let it dry. Then use a conformal coating to seal it. Use a coating that is intended for electronics and that can be removed if you ever need to repair the circuit.
Tom
Tom
Hi folks,
The intention was to use the DAC outdoors, hence the idea for protection. But even if potting is excluded and replaced with a layer of conformal coating, what about the dielectric constant change?
The intention was to use the DAC outdoors, hence the idea for protection. But even if potting is excluded and replaced with a layer of conformal coating, what about the dielectric constant change?
There exists potting material especially designed for encapsulating sensitive electronic assemblies. It remains widely specified for use in almost all aerospace and aviation platforms. It is however specialized and therefor expensive. It guarantees resistance to shock, anti-vibration, ingress of liquids inert to temperature fluctuation, does not stress any components while curing, etc. etc. The potting can be removed by a chemical processes if needed.
Do not use off-the-shelf epoxies they are not suitable for this purpose, you would end up throwing your circuit away. If used outdoors rather place the equipment into a suitably IP rated enclosure with wiring entry and exit glands for the required environment.
Do not use off-the-shelf epoxies they are not suitable for this purpose, you would end up throwing your circuit away. If used outdoors rather place the equipment into a suitably IP rated enclosure with wiring entry and exit glands for the required environment.
You said the right word, conformal coating, it conforms to some specification for application. Not any varnish painted onto it. Even conformal coating done should follow the application guidelines, such as dipped while vibrating the liquid and oven drying.... Why make your project difficult. Just make a spare PCB board should it fail one day.
How do you see dielectric constants changing? Will you measure capacitance over a unit area and calculate dielectric constant then analyze the circuit performance mm by mm? Would this affect the circuit overall performance at all? Probably not.
Would ingress of water and other contaminants such as fingerprints, solder flux and so on deteriorate performance on the long run? Probably yes.
Would ingress of water and other contaminants such as fingerprints, solder flux and so on deteriorate performance on the long run? Probably yes.