Bonding of laser diode chips onto substrates
Lasers in general show a poor wall plug efficiency. Due to its principle of directly converting electrical energy into photon energy semi conductor lasers have the best electrical to optical efficiency of its kind. However, still a vast amount of energy is not converted into light but into heat instead.
The life time of such elctro-optical products like laser diodes or high power LEDs is negatively influenced by the operating temperature of the semiconductor chip disproportionately where a none cooled chip immediately dies. A good heat dissipation therefore is mandatory for a working laser diode. Furthermore the emitted wavelength is a function of the chip temperature. One can easily imagine that the individual emitters of a laser bar will have different wavelengths if the bar is not cooled homogeneously.
For those reasons the brazing or soldering process to bond the die to its heat sink is extremely crucial. The more attention is brought to this production step the longer the life time and the higher the quality are adding more value to the assembled product.
For the quickest and within the best heat dissipation the bond line thickness should be as small as possible. Furthermore, a bond line which is not evenly thick will lead to unwanted effects such as wavelength broadening and needs to be prevented.
ficonTEC’s BondLine machines control the parallelism of the chip to its heat sink by a clever interaction of high precision metrology and offset actuators. The process is computer controlled so that each pair of chip and heat sink gauged and adjusted individually. Similar metrology is used to adjust the overhang leading to a bonding process with six degrees of freedom. The bond tool can provide a force to the die and within precissely controls the bond line thickness. To account for different material combinations, component geometries, soldering philosophies, etc. the temperature profile is freely programable. The ideal machine for this is the ficonTEC BondLine.
Most significant machine modules:
Flip Chip Station