SYRCAPE

Driven by innovative and miniaturization needs for future missiles and smart ammunitions, the thermal management of on-board electronics will have to overcome some of the drawbacks related by traditional cooling solutions currently used in such systems. Based on microsystem technologies, new solutions embedded as close to the electronics, directly into the printed circuit boards (PCB) provide interesting solutions as they meet both reliability, cost and integration requirements especially in harsh military environments (wide temperature range, vibrations, high acceleration). Fluidic cooling systems, also called heat pipes, demonstrate outstanding performances in terms of thermal conduction. Even if direct integration of them in PCBs seems possible as related by different patents, they are still commonly used as external cooling solutions. Despite their high cooling performances, heat pipes also exhibit some challenging weaknesses. First, they are highly sensitive to acceleration due to their working principle based on the capillary pumping of the coolant fluid. Furthermore, implementing such devices requires the use of heavy and cumbersome interface plates so as to make relevant efficient thermal exchange. These constraints, in addition of costly operator-dependent assembly steps, confirm that the use of heat pipes for on-board electronics is not trivial. However, improvements are still possible in this domain and we propose to investigate some of them in this project. As part of this project, a consortium involving C2N (University Paris-Saclay), MBDA Group and EGIDE Company was being set up. The aim is to design, realize and characterize an innovative cooling system, providing both high performances, compactness and reliability, with a targeted TRL of 4. The proposed fluidic cooling device can work using monophasic mode and two-phase mode even if it is not optimized for at first sight. Here, most parts of the fluidic system are embedded in the bulk of the PCB without increasing the thickness of the electronic board. The pumping mechanisms is ensured using an innovative MEMS pump. This device, in the form of a module, will be soldered as the other components at the PCB surface. So, in this way, the pumping will not be ensured by capillarity but will be electrically assisted and will not be subjected to acceleration limit. Most parts of the system are realized using an innovative thermocompression (Cu/Sn/Au/Cu) technique during PCB manufacturing without any modification of the process. This technique allows the realization of thin metalized free shape cavities and so an efficient way to create a perfectly sealed fluidic loop. Based on a THALES patent, this process is provided using a license for exploitation owned by the MEREDIT consortium in which MBDA is a partner. Apart from the fluidic aspect, one of the main challenges is highly linked to the pumping system. In order to set in motion the cooling fluid meeting both, high efficiency and harsh environments needs, we plan to use a micro-pump based on the Electro-Hydro-Dynamic (EHD) phenomena. Such devices are known to be non-mechanical pumping systems, offering extremely high robustness compared to traditional mechanical ones. The innovative 3D module, in ceramic, is manufactured using a well-known Temperature Co-fired Ceramic (HTCC) process thanks to the EGIDE expertise. The pump is then mounted at the PCB surface as a classical component by brazing, allowing a long term hermeticity of the whole fluidic loop. In addition to a heater and a Peltier TEC to mimic the chip to be cooled and the cold point, the final demonstrator envisaged, as close as possible from the industrial solution, will include a set of temperature sensors. This test strategy will allow us to characterize as finely as possible the whole system, in an automated manner over a long period of time.