What is the release behavior of a solder paste? And what happens if it stands for a longer period of time? Application team leader Robert Miller at Heraeus Electronics deals with questions like these in order to carry out precise tests on the solder and sinter application materials.
What is the perfect recipe for solder and sinter pastes? Which one prints better on which material? And if the print is good - which soldering profile is required? The developers at Heraeus have several laboratories in which the complete SMD process can be simulated: "We use various test methods to test the solder pastes and their behavior in all process steps," says Robert Miller. In order to be able to analyze the printing process, the Heraeus development center in Hanau purchased a 3D solder paste inspection system (SPI) from the Korean supplier of inspection solutions for electronics production Koh Young in 2023.
During the selection process, Robert Miller completed several tests at SmartRep, Koh Young's German distributor. He was impressed by Koh Young's measurement technology: "We have exact 3D values and know the exact volume of solder paste on each pad." Together with Benjamin Blank from SmartRep, he configured an SPI system with a very high camera resolution: "The aSPIre3 has a resolution of 10 µm, so we can evaluate the wetting tests in great detail." The piezo strip grating technology used is supplemented by four projectors, so that absolutely shadow-free measurements are possible. Because the accuracy of the measurement results is crucial, the automatic compensation of PCB warping during each measurement is also an important aspect of Koh Young technology. The system can even take into account height differences between the pad and the solder resist.
Statistical analysis
"While SPI systems are primarily used for pass/fail testing in the SMD process and are controlled via process windows, SPI has a different function in the development department," says Benjamin Blank, who accompanied the benchmark. The error messages are a source of knowledge here. This is why the SPI system is set very sharply so that the smallest deviations are detected and compared with each other: How does a solder paste behave on gold, tin and copper pads? "This goes far beyond the usual IPC specifications and shows how precise Koh Young technology is."
In addition to the simple software interface, it was important that the SPI data could be used for further evaluations. Blank: "We naturally carry out repeatability tests and examine the scatter. With the 'SPC Plus' tool, Koh Young offers real-time evaluation options and a large database. This is because many values are recorded: surface wetting, volume, coplanarity, etc. However, it was also important for us to be able to easily integrate this data into other statistical tools, where we can combine it with other data."
Robert Miller from Heraeus drew a positive balance after a few weeks of testing. The support and fast response from SmartRep were excellent, so the decision was made to invest in the device.
Heraeus Electronics develops and produces materials for assembly and connection technology in the electronics industry. Heraeus Electronics is a provider of material solutions for the automotive industry, power electronics and the semiconductor market. Its core competencies include metal-ceramic substrates, bonding wires and tapes, solder and sintering materials as well as thick film pastes. They are produced at eight production sites in six countries.
www.heraeus.com
www.kohyoung.com
www.smartrep.de
