Reliability Of Die Bonding Layers In High Power Diode Laser Packages

High power laser diode(HPLD)have been widely used in many areas including solid-state laser and fiber laser pumping,medical cosmetology,projection display,material processing,and infrared lighting due to small size,light weight,high efficiency,high reliability,large wavelength range and low cost,etc.As an intermediate structure connecting chip and bottom heat sink,the die bonding layer not only functions as a mechanical connection and an electrical connection,but also buffers the stress-strain relationship between the chip and the heat sink caused by the CTE mismatch.Thermal shock,vibration impact,and electrical pulse cycling can cause creep and plastic deformation inside the interconnect interface material,which lead to voids and cracks,and ultimately affect HPLD's output laser power,spectral beam quality,storage lifetime as well as operation lifetime.Therefore,studying the reliability of high power laser diode's interconnection interface,especially the reliability and effective life of the interconnection interface under thermal shock and extreme ambient temperature conditions,has very important theoretical and practical application value.This paper mainly studied the failure mechanism of the die bonding layer under thermal shock and extreme temperature operating conditions,established the fatigue failure process and life prediction model for interconnected interfaces of high power laser diode arrays under different conditions,different material compositions,and different temperatures.The specific research work is described as follows:(1)Completely simulated the fatigue failure process of the CS device encapsulated in In material at-55°C~125°C(228 K~398 K)cycle thermal shock based on the unified visco-plastic Anand constitutive model and Darveaux life prediction model.By analyzing the distribution and variation of the stress and strain in device's interconnection interface,the position of the“most dangerous unit”has been located at the edge of the interconnected interface away from the center position.Meanwhile,the interconnected interface's failure mechanism under conditions was summarized according to the prediction result of crack generation and diffusion.(2)The lifetime of interconnected interfaces at different light-emitting positions of CS devices under the condition of-55°C~125°C cyclic thermal shock is predicted.The results show that the interconnected interface region located at the position of edge luminescent point is the most prone to fatigue failure and has the shortest lifetime reaching 3006 cycles;the lifetime of the interconnect interface located at the central luminous point is the highest which reaches to 171131 cycles.It is calculated that the lifetimes of the three different CS devices'interconnection interface materials including In,80Au20Sn and nanosilver pastes of under cycle thermal shock conditions from-55°C to 125°C is 3006,4080,and 4911 cycles respectively.The result indicates 80Au20Sn and nanosilver paste have superior reliability and stability in a thermal shock environment with a large temperature gradient compared with In,and are more suitable as interconnection interface materials.(3)The working process of quasi-continuous(QCW)808 nm MCC semiconductor lasers with a peak power of 700 W,a pulse width of 500?s,a frequency of 60 Hz,and a duty ratio of 8%was simulated in normal temperature(25°C)and cryogenic environments(-70°C),respectively.The stress and strain distribution of the laser interconnect interface after 15 pulses was established.The failure criterion of the interconnect interface of the semiconductor laser was established,and the interface life criterion of the high power semiconductor laser interconnect required in the actual project was compared and analyzed.The results show that the working life of the interconnect interface of the quasi-continuous MCC semiconductor laser can reach 1.36×10~9 pulses at room temperature,which is higher than 1×10~9 pulses of the engineering application standard;meanwhile the lifetime of the interconnect interface of the quasi-continuous MCC semiconductor laser at-70°C is only 6.55×10~8 pulses and cannot satisfy the working requirements under extremely low temperature conditions.The established quasi-continuous working life prediction model provides valuable data for HPLD fatigue testing experiments conducted in cryogenic environments in the future.