Dr. Bruce Scruggs, Product Manager Micro-XRF, EDAX
We recently received an order for an SMX-ILH unit and I thought this would be a great topic to blog about having been involved for many years in XRF laboratory instrument installations and now participating in the planning phase for integration of an SMX-ILH into a manufacturing process control setting.
The SMX-ILH unit is an XRF measurement tool capable of measuring layer thickness and layer composition of multi-layer stacks on treated panels, printed circuit boards and spooling sheets of metal. Typical applications include photovoltaic layers on solar panels, electrical contacts on printed circuit boards and metal finishing treatments on sheet metal. In this particular case, we will be integrating an SMX-ILH unit into a solar panel manufacturing facility and we have to deal with a number of issues involved in making measurements on glass panels anywhere from nominally 0.5 to 1.5 m on each side during an automated manufacturing process.
To start, the solar panels are transported from the coating process to the SMX unit via a conveyor system. We need to integrate the SMX into the manufacturing conveyor line to coordinate the flow of the panel in and out of the measurement unit. The panels are serialized as well; so, before loading the panel, we need to read a barcode to identify the panel and tag the measurement results with the panel’s serial number. Once the panel is loaded, we need to account for the temperature of the panels coming out of the coating process as they are typically at elevated temperatures above ambient. Given general requirements on measurement throughput, there’s no time to let the panels cool. In this situation, we equip the XRF measuring head with a patented thermal shield to reduce temperature fluctuations around the measuring head detector which could affect the stability of our measurements.
Next, we need to account for the planarity of the glass panels. Panels of this size are not perfectly flat. There is always a certain amount of bow and warp which would affect the distance between the sample and the measuring head and, consequently, the measurement results. We handle this by adjusting the position of the measuring head with an automated, laser-based auto-focus. This also accounts for the flatness of the conveyor system. We can level off the conveyor but we also have to account for tolerances in the concentricity of rollers of the conveyor inside of the SMX unit. Once the measurements are completed on a particular panel, the results can be uploaded into the factory’s MES system.
This covers the aspects of getting the panels into the SMX, measuring them and getting them out of the SMX. But, we also need to control the SMX unit. The SMX’s SW is tiered for 3 levels of users. The Supervisor level allows for measuring recipe development and calibration. The Operator level allows the general SMX operator to load and run measuring recipes but protects these recipes from unauthorized alterations. Finally, there is a Service level in the SW to allow maintenance engineers and applications experts to check and calibrate the operation of various instrument components.
Having developed and calibrated the initial recipes for measuring these photovoltaic formulations on a benchtop unit, the SMX-BEN, using small sections of glass test panels, it’s really interesting to see all of the various aspects that have to be covered in making the same measurements on “life-size” panels in a process control/manufacturing environment.