The method of potting in a vacuum
This method works
Unlike than a technical vacuum with its strong negative pressure, vacuum potting of electronic components only reduces pressure to a maximum of 1 mbar. And with good reason: Reducing the atmostpheric pressure any further results in a longer evacuation time and higher energy costs. The vacuum should therefore be specifically adapted to the particular task.
Even the size of the chamber to be evacuated (the component size is a factor in this case) affects the evacuation time: the greater the volume of air, the longer the evacuation cycle.
With a view toward ever shorter cycle time requirements, the use of high-performance vacuum pumps today allows for optimal evacuation times. The greater the volume of air, the longer the evacuation cycle. With a view toward ever shorter cycle time requirements, the use of high-performance vacuum pumps today allows for optimal evacuation times.
A slight negative pressure also has its advantages in terms of component stability. Not every component can handle a sharp drop in pressure. While coiled material is for the most part unaffected by such conditions, air trapped in a capacitor can cause the component to crack under external negative pressure. Usually the negative pressures during vacuum potting are between 2 and 100 mbar.
This alone is not enough to be completely free of air bubbles. At these pressures, traces of air trapped by the potting material can still be found in the component.
This air must be eliminated through the potting sequence and must be displaced completely by the rising potting material.
What happens inside vacuum chamber?
The potting process always takes place in a vacuum chamber – particularly in case of coiled material – in 3 steps:
1. Initial filling with potting material in a vacuum
2. Intermediate venting to press material deeped into the coil
3. Finishing layer in a vacuum
1. Filling in a vacuum
The potting material starts to fill the small gaps between the wires.
Notice - The process steps in the example of potting a coiled product
2. Intermediate venting/pressurization
Intermediate venting increases the pressure inside the chamber. This drives the potting medium deeper into the small spaces.
3. Finishing layer in a vacuum
The finishing layer ensures that the component is evenly coated with the potting medium.
These finely coordinated substeps are controls by cutting-edge system controllers. The intuitively operated system controllers visualize all relevant machine data (for example, target and actual vacuum values, good and bad parts, processing times, machine availability). The metering and dispensing system can also be connected to higher-level customer controllers (customer server), for example to exchange data and to control multiple system components centrally using one system. For optimum quality assurance and traceability, all relevant control data is documented and, if required, exported.
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