Alpha has developed advanced alloys for improved thermal stability and reliability for high temperature operation and higher thermal fatigue and vibration resistance, the first of which is known as the ALPHA MAXREL alloy.
Available in solder paste, preform and wire format, the ALPHA MAXREL alloy has proven very effective for LED Chip-on-Board (COB) Assembly applications, where high CTE mismatch can exist between the die stack and substrate, and creep fatigue properties of the solder material are important.
“It has been shown that the ALPHA MAXREL alloy maintains excellent shear strength even after 1000 thermal cycles under high CTE mismatch conditions,” said Ravi Bhatkal, Vice President, Energy Technologies at Alpha. “In the case of high power LED assemblies, such as for outdoor lighting or automotive applications, the CTE mismatch is quite high, causing significant strain energy build-up during thermal cycling, in the solder joint between the LED die and the Metal Core PCB. This can cause micro-cracking and eventually failure of the joint. It is therefore important to use alloys that will create strong solder joints with improved thermal fatigue/creep and vibration resistance to ensure long-term reliability.”
A variety of die attach materials, including solder, conductive adhesives, or sintered materials can be used to bond LEDs to the substrate, depending on requirements. In addition, Alpha offers ALPHA Lumet P39 Solder Paste with MAXREL Alloy to enhance reliability for high-power LED COB assemblies.