Improved Thermal Performance Of 3D Opto-Electronic IC Assembled on Multiple Interposers Through Design Optimization

In this work a Co-Packaged Optics-FPGA-Memory-Power supply 3D module, “LightSiP™, a System-in-Package is presented. The paper focuses on the critical issue of Thermal management and Warpage encountered in the LightSiP™. The paper presents the issues created by run-time temperature increase and deformation and how to overcome these obstacles. A multi-interposer hexagonal System-in-Package called LightSiP™ has been developed, integrating optical transceivers and programmable logic devices within a single package. The interposer layer contains two Intel Arria 10 FPGA silicon dies surrounded by twelve optical interconnects, known as LightKonnect™, each supporting 192 Gbps of data bandwidth distributed spatially. Layer-2 (Digital Layer) includes 32 GB DDRAM, an MAX10 as the system controller, and clock generators. Layer-3 (Analog Layer) houses all the power micro-modules. The power dissipation of the entire LightSiP™ is 174 watts and power distribution starts from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3^{\text{rd}}$</tex> layer to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1^{\text{st}}$</tex> layer. The transfer of electrical power occurs from the 3rd layer to the 2nd layer via Board-to-Board (B2B) connectors, and from the 2nd layer to the 1st layer via solder bumps. An intense research and multiple thermal and warpage simulations are performed for different Thermal Interface Material (TIM), solder bumps, pins, and stiffeners. The component's temperature has been reduced by 25% - 30% from the initial values. The deformation has been reduced to a minimum which is less than the smallest component present in the LightSiP™. The material study is paramount for both thermal and warpage analysis as the material's mechanical properties decide the structural integrity of LightSiP™ and heat transfer of the components. The temperature control of components with heatsink and forced convection and the optimization of deformation of LightSiP™ with stiffeners along with the help of proper material selection is presented.