FFU and EFEM/Mini-Environment Status and Exception Alarming
Our custom engineered FFU on an EFEM or on the tool itself provides the necessary volume of ULPA filtered air to pressurize the space to what is typically a 0.005”-0.01” WG. differential pressure when compared to the surrounding environment. IF anything happens to the differential pressure it is critical that the tool owner is informed immediately, otherwise the “alarm signal” ends up being bad wafers down the line. The following section details some of the many ways that we report the status of both the FFU itself, and the EFEM/Clean Zone/Mini-Environment. Please keep in mind that this is just a short list of the typical ways we report the status, and we are happy to work directly with you to meet your needs if you find they are different than what is detailed here.
Note: The listed below starts with the simplest/least expensive option and continues with options that offer more and more information.
- The simplest status reporting option is a green light comes on when the fan is powered on via the analog on/off speed control. The most common form of FFU failure (hard to imagine, but true!) is someone simply deciding to turn the FFU off as often the on/off speed control is in plain sight. Without the presence of a green power light being lit they may in fact not even know they turned the FFU off.
- Often the green light as shown above can be matched with a sensor that measures the pressure that each normally operating fan develops, and the red light illuminates if fan failure is sensed.
- Same as above, however the lights are remoted for installation by the customer to a place on the tool of their choosing. On the FFU are labeled connectors that correspond to the RED/Green lights
- The most common sensor in our FFU products is a simple switch that changes state when the pressure at the inlet of a normally functioning fan develops enough negative pressure relative to ambient to make the switch change state. When a fan failure is to be reported red light, as above, the switch is of the Normally Closed variety. It then switches to open when the fan spins up and only returns to the closed state if a fan fails. This completes the circuit and the fan failure light illuminates. Alternately, the status of the fan failure sensor can be run to a connector on the FFU body for monitoring by the tool. We apply one of these sensors per fan in the FFU.
- For more expansive reporting we feature a module that can be face mounted on the FFU or a panel on the tool, or surface mounted in its own cosmetic case. With this product you can report and display temperature, relative humidity, differential pressure and (with a caveat of how it is displayed) fan failure.
Panel mount (on FFU or on a tool location):
High and low warning and alarm levels can be programmed directly into the unit for all monitored parameters. When all parameters are in specification the display is green, as shown below. When a warning or alarm is detected the screen turns red and then based on the customers preference, the unit can be programmed to audibly alarm and/or close a dry contact.
ALARM LOW LIMIT
Sets the low pressure alarm limit
- With our digital control solution, the Variphase from our controls partner Air-Care Automation, lots of system status data can be exported via Ethernet, DeviceNet, BacNet ModBus RTU, ModBus ASCII, and others. These include fan speed, RPM, system pressure, temperature, relative humidity. This typically involves a lot of customer involvement in developing an interface in the GUI of the tool so please contact us if you are interested in developing this sort of capability