In general, relatively smooth surfaces with R a < 5 µm and R z < 20 µm can be obtained by eutectic-bonding, active-metal-brazing (AMB), and metal-casting-direct-bonding (MCB) method etc. The surface roughness is typically characterized using arithmetical mean surface roughness ( R a) and maximum roughness depth ( R z). The Cu surface could have a wide range of surface roughness due to the various processing techniques for bonding Cu sheets on ceramic insulation layer during DBC substrate manufacturing,. It has been reported that the strong die-attach on low-cost copper (Cu) surface can be obtained by pressureless silver-sintering in air, which has great significance in power electronics. With the development of wide-band-gap devices targeting for high-temperature and high-power applications, die-attachment by low-temperature sintered-silver was increasingly used as an alternative to solders or epoxies, due to its high-performance and high-reliability,. This work could help to prepare DBC substrates with optimized surface roughness to accommodate the viscosity, the particle size, and the sintering shrinkage of the silver paste for well using the sintered-Ag die-attach technology. When the surface roughness ( R a of 0.65 μm) is slightly larger than the silver nanoparticles (diameter of 0.6 μm), the high shear strength in excess of 50 MPa was achieved, likely due to both strong metallic bonds and mechanical interlock. In this study, we did die-attach on Cu substrates with surface roughness R a = 0.15–8.41 µm and R z = 1.22–50.97 µm by pressureless sintering of nanosilver paste in air. It is crucial to find out how the surface roughness influences the bonding strength of the sintered-silver (Ag) die-attachment. The Cu surface in direct-bond-copper (DBC) substrates could have a wide range of surface roughness due to the various processing techniques. Laser Gold came to the attention of the Academy of Motion Picture Arts and Sciences, and this hard, pure, space-qualified gold plating has been "dressing" the Oscars for the last three award seasons.It is significant to attach power devices on low-cost copper (Cu) substrates by pressureless silver-sintering in air. NASA is currently using Laser Gold because of its peerless heat reflecting properties and has specified this process for thermal control on countless spacecraft instruments beginning some 35 years ago to the early GOES weather satellites as well as the Hubble camera housing and more recently, on both the near- and mid-infrared cameras aboard the James Webb Space Telescope. That effort culminated in this NIST designation." After a successful sample, Xerox tooled our company with a $60,000 infrared spectrophotometer which gave our engineers the 'eyes' to inspect the reflective performance of the gold plating and continuously tweak the process to achieve higher and higher reflectivity. That's why Xerox copies come out of the machine warm.Įpner continued, "They were having difficulty finding a supplier whose plating could withstand the extreme heat of the lamp without blistering the plating off the aluminum while also meeting their reflective requirements. "Xerox needed a gold-plated aluminum reflector behind a quartz infrared lamp which generated the heat that fused the toner onto the paper. "It all started with a chance meeting with a Xerox engineer at a 1972 trade show which took our 65-year-old company into the world of high technology electroplating for infrared reflectivity," said David Epner, president of Epner Technology. The new gold standard entered the NIST catalog of Standard Reference Material as SRM #1929. The result was an astounding 99% throughout the mid-infrared range of 2 to 14 microns. The specific instrument used to measure the standards is the "Infrared Reference Integrating Sphere (IRIS), which is described here. The Gaithersburg, MD laboratory in which the reflectance measurements are preformed is the "Fourier Transform Infrared Spectrophotometry (FTIS)" facility, which is described here. NIST calibrated some 20 copper mirror substrates that had been single-point diamond fly cut to a surface roughness of 50 Angstroms by the Kugler Group (Salem, Germany) and then plated, first with pure nickel followed by Laser Gold, each about a micron thick. The process is unique in that it is both ultrapure (.9999), while also three times harder than any other 24 Kt. Laser Gold is a proprietary electroplated process developed by the hundred-year-old New York precious metals plating firm, Epner Technology (Brooklyn, NY). The National Institute of Standards and Technology (NIST) has once again selected Laser Gold as the new gold standard for infrared reflectivity.
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