Solid State Relay Thermal Analysis And Research

Solid state relays have unique advantages in a wide range of applications in the fields of av iation,aerospace,and weaponry.However,when the solid state relay is working normally,there is a certain power loss of the internal components and chips.This power loss is mainl y determined by the output voltage drop and the load current,and is consumed in the form of heat,thus increasing the power consumption of the solid state relay.At the same time,it causes damage to components,which reduces its own life and reduces reliability.In order t o extend the life of the products and improve its reliability,this topic is intended to conduc t thermal analysis and research on solid state relays.This paper analyzes the metal casing bulging and bursting phenomenon of the solid state re lay during assembly,test and user use,and confirms that it is caused by overheating inside the product.Therefore,the 4JG7-1B DC solid state relay,1JG60-4 DC solid state relay(Cl ass I solid state relay,assembled by discrete devices)and JGC-3031 optical-MOS solid stat e relay were studied and analyzed respectively.Conclusion as follow.1)The Ron(on-resistance)of the Field effect transistor(FET)can determine the thermal e nergy generated by the solid state relay;the smaller the Ron,the smaller the heat energy ge nerated.Therefore,if the conditions permit,the FET Ron should be as small as possible.2)The resistivity of the lead rod material can determine the thermal energy generated by th e solid state relay.The smaller the resistivity,the smaller the heat energy generated.Theref ore,if the conditions permit,the smaller the resistivity of the lead rod material is selected,t he better.It is recommended to use high-conductivity oxygen-free copper as the inner core material and 4J29 alloy composite material as the outer skin material to replace the 4J29 ex panded alloy wire.3)The diameter of the bond wire can determine the thermal energy generated by the solid s tate relay.The larger the diameter of the bond wire,the smaller the heat energy generated.Therefore,the larger the bond wire diameter selection,the better,if conditions permit.4)The external environment cannot determine the thermal energy generated by the solid st ate relay,but it can determine the heat dissipation of the solid state relay.Therefore,if cond itions permit,it is recommended to control the temperature of the solid state relay.5)When the external auxiliary heat is dissipated,the output capability of the solid state rela y can be improved.6)The smaller the thermal resistance of the heat sink,the better the performance and the better the heat dissipation of the solid state relay.7)The thermal stress fatigue life of the solder joint formed by the eutectic solder joint is un iform and consistent throughout most of the solder joint(the fatigue life is basically 106 ti mes);and the conductive silver paste is cured at a high temperature.The thermal fatigue lif e distribution of the formed bonded body is uneven,and the fatigue life cycle is large.In th e field of missiles and arrows,it is recommended to apply the eutectic bonding process to b ond bare chips to ensure the thermal reliability of the product under high temperature and l ong-term work.8)For the simulation model with multiple identical unit modules,the whole simulation mo del can be simplified by the minimum model method,so as to reduce the calculation amou nt and calculation time while ensuring the correct and consistent calculation results of the s imulation analysis.