Encapsulating with EVA

[Mike90250]

do we really need EVA sheet in front of solar cells?

I don't know for sure. You could read the post just before yours, and see if the answer is more clear.

[bcroe]

do we really need EVA sheet in front of solar cells?

Silicon semiconductor devices are always in an airtight package, because otherwise moisture would
destroy them in a fairly short time. This includes solar cells. Bruce Roe

[littleharbor]

I would think , besides fully encapsulating the cells, the front EVA sheet would cushion the cell and prevent it from cracking while under vacuum. With the soldered tabbing and inter cell connections there is no way the cells would lay perfectly flush against the glass.

[foo1bar]

Silicon semiconductor devices are always in an airtight package, because otherwise moisture would
destroy them in a fairly short time. This includes solar cells. Bruce Roe

Many many semiconductor devices are not in airtight packages.
Most likely the CPU you're using to read this (and the web servers' CPUs ) are not in airtight packages.

Most server CPUs have packages that the back side of the die is directly exposed - the heat sink for the system directly contacts the back side of the die.
Even for older CPU packaging where there is a metal slug as part of the package the package isn't air-tight. The air inside it goes significant temperature increases (ex. 20C to 70C in minutes) So I think even small amounts of trapped air could create enough force to force things apart. Those types of packages usually had a built-in air hole/channel to equalize pressure inside and outside.
If you go back even further to 386/486 timeframe, those packages were probably air-tight - they had a cavity that would be filled in with an encapsulant after the wirebonding was finished.

But the general idea that you don't want moisture on semiconductor devices (including solar cells) is true.

[bcroe]

Many many semiconductor devices are not in airtight packages.
Most likely the CPU you're using to read this (and the web servers' CPUs ) are not in airtight packages.

Some devices have what is called glass passivation. This protects what appears to be a bare
die. No doubt there are other methods I have not kept up with. Protection is necessary.
Bruce Roe

[Mike90250]

EVA is a VERY special plastic hot melt glue / sealant. It's special property is that is impervious to water vapor (and quite UV resistant). Water vapor is not stopped by paints, or most epoxies. Water vapor zooms right through silicone sealant (it's a cure agent for most silicone in a tube products)