the ceramic surfaces an ultrasonic transducer thermosonic metal to metal interdiffusion process may be used to apply a downward pressure to the dies 125 and rapidly vibrates the dies 125 with respect to the submount 130 so that the atoms from the opposing bonding metals merge to create an electrical and mechanical connection between the die 125 and the submount 130 other methods for led die to submount interconnection can also be used such as using a soldering layer during die attach process e g with an au u2014 au interconnect the substrate temperature is maintained above e g 40 50 u00b0 c the glass transition temperature tg which causes the underfill material to be in the elastic stage to soften and comply with the leds and to prevent the formation of voids subsequently the underfill layer is permitted to cure at approximately the glass transition temperature e g 200 u00b0 c for 1 2 hours in order to harden the submount 130 can then be scribed and singulated to form leds 140 as illustrated in fig2 e in another embodiment the growth substrate 102 is not removed until after the wafer is separated into separate dies and mounted to the submount 130 as illustrated in fig5 a 5 b and 5 c as shown in fig5 a the sapphire substrate 102 with led gan layers 104 are scribed and separated into individual dies 150 the scribing.