Stop potting. Based on my 35 years experience in electronics it is difficult to make it work properly without causing quality issues. It is also a nightmare for the factory processes.
And it brings you no benefits - only costs you reliability!
I think your stated reason was to stop your competitors reverse engineering your designs. It won't. One person (on his own) has managed to reverse engineer the PA5 module to enable people to repair their own amplifiers.
I won't add what I think about toppings CS that made that necessary.
Thanks for saying this, so true.
Examples:
When encapsulating, if there is any manufacturing residue (like solder flux), the encapsulation will typically cause the residue to be an early time to fail.
Also, if there are any electromechanical marginalities in the manufacturing (like bad solder process), encapsulation will typically accelerate/exacerbate the fail. This will show up in early life fails.
Even if the manufacturing process is flawless, encapsulation puts additional thermal and mechanical stress reducing the useful life time. If the manufacturing flow leaves behind stuff like solder flux, then add chemical degradation and new sources of gasses and defects and other insidious mechanisms to degrade your product.
Things get 'potted' for various reasons.
@JohnYang1997 mentioned power supplies... High Voltage power supplies are potted or encapsulated in dielectric materials that prevent a range of behavior, but those materials are often gel or even liquid. And most of the encapsulated devices aren't a bunch of surface mount parts stuffed onto a board. And some HV encapsulations are designed to improve thermals, not degrade.
Other things get encapsulated for environmental reasons, like when seawater or corrosive stuff is the main enemy. In this case, encapsulation makes sense even though the encapsulated component is going to cost much more and almost assuredly will have a shorter maximum service life compared to an equivalent component that is not encapsulated. Of course, the non-encapsulated component fails quickly in the corrosive environment, but it almost always pays a penalty in maximum lifetime. And of course costs much more. And many of these manufacturers have a pre-production model of the encapsulation, and test that model prior to production qualification, and plan on making changes prior to production release, and even include test structures to monitor fail modes in that pre-production reliability run.
Topping
@JohnYang1997 appears to be doing the encapsulation for IP. I understand the reasons, and am a bit heartbroken. But to be serious, any competitor can de-lid your encapsulation and reverse engineer in a few hours (
@gamerpaddy did just for fun
). So you don't protect yourself one bit, sorry to say. And you pass reliability onto the customer, double-sorry to say... And I see you are even trying to do some extended life testing to figure out what is going on, which is commendable. If you feel you have a handle on the interaction of the manufactured component with the encapsulation, fine. But even a change in vendor of potting compound, or change in board design, or change in board manufacturing process, or a tool or process running out of spec... all will introduce customer returns... where a non-encapsulated device would be fine.
I have some pain on this. I was one of the early PA5 buyers. I also bought a D30Pro and A30Pro. Sadly, the PA5 succumbed to
the defect. I had a very bad experience with one of the resellers, I think you helped get that resolved, and I appreciate. I also had the A30Pro go bad, and I think you may have directly or indirectly helped since the reseller refunded my money after first dragging me out... Much of my frustration is with the resellers so thanks for your
recommendation. But, for sure some of it is with the intrinsically unreliable PA5.
In summary:
I would ditch the potting.
I would enforce discipline on the resellers since they play a role in your Brand.
