Dr. Patrick Camus, Director of Research and Innovation, EDAX
You may have heard of a new breed of SDD that has an ultra-thin Silicon-Nitride (Si3N4) window. Its main advantage over traditional polymer windows is its significantly higher low-energy sensitivity. In addition, it is both moisture and plasma-cleaning tolerant which permits the true vacuum sensor environment to persist for the lifetime of the detector.
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.
Dr. Katherine Rice, Applications Scientist at CAMECA Instruments, Inc.
Dinner at the top of the Park with a view of the Wisconsin State Capitol
The Terrace at the University of Wisconsin
Last week was a great week up here in Madison for our bi-annual users’ meeting, with about 90 atom probe enthusiasts making the trek to Madison, WI to discuss the finer points of atom probe tomography (APT). There were plenty of great sessions involving, for example, correlative microscopy, cryo-atom probe, and new ways to detect evaporated ions. Lest anyone think that we are too serious up here in Wisconsin, we also enjoyed talks on atom probing rodent teeth and even beer, as well as having several social events where our attendees could sample local brews.
Demo attendees watching a map being taken
Many of the users have been implementing transmission EBSD (or TKD, as some folks prefer) on their needle-shaped atom probe specimens which are typically shaped by a focused ion beam (FIB) microscope. This allows for identification of any grain boundaries present, and also helps position a grain boundary close to the specimen apex so there is a good chance it will be captured in an APT analysis. Atom probe specimens usually have a radius of ~100 nm which makes them ideally sized for transmission EBSD at SEM voltages between 20-30 kV. The users’ group meeting also marked another special event: the debut of Atom Probe Assist (APA) mode in the TEAM software. Transmission EBSD can be challenging, but APA mode makes the analysis faster and easier by implementing recipes for background subtraction developed by EDAX and by skipping mapping of areas not intercepted by the specimen. We had about 20 users at the Tuesday demos of APA mode and another few at an additional demo on Friday. CAMECA’s Dr. Yimeng Chen manned the FIB and quickly targeted a grain boundary for FIB milling while our EDAX friend Dr. Travis Rampton took maps after each milling step to make sure the grain boundary was contained in the specimen.
Yimeng Chen and Travis Rampton present a poster.
Sample holders that work well for t-EBSD and FIB were also on debut at the meeting. Many of CAMECA’s atom probe users mount up each specimen to our Microtip coupons, which are 3 mm X 5 mm pieces of Si that hold 22 flat topped posts. Our Microtip Holder (affectionately nicknamed the Moth) was developed to do transmission EBSD on each of 22 mounted specimens, and then transfer the stub portion directly into the atom probe. Even if you don’t do APT, these microtip posts are a convenient way to mount multiple thin samples for transmission EBSD.
The moth sample holder containing a microtip coupon
It was incredible to see the explosion of transmission EBSD for atom probe, and the cool things that many LEAP users are discovering when they try it out on their atom probe samples. Perhaps the greatest strength of this technique is how easy and integrated it is in the atom probe specimen preparation process. You don’t even need to move your sample or the camera between steps when you are shaping a liftout wedge into a specimen that is atom probe ready. I look forward to hearing about the new applications that are being discovered when combining t-EBSD and APT!