Design And Implementation Of The Miniaturization Of Class 2 Solid Relay With Double Structure

Solid relay is a contactless relay which composed of electronic components,integrated circuits and hybrid integrated circuits.It is a kind of power electronic switching circuit which applicated in the fields of automation control widely,such as aerospace,weapons and ships,computer control and motor control,etc.Class-2 solid relays are assembled with discrete components,film fixed resistors and chips via hybrid processes,and the chips and leads are bonded.Generally,solid relay is switched on at about 30?s.If pulse with interference is input,error operation is easier for liable to be activated.Therefore,anti-interference function should be added.Two-layer structure is commonly used in domestic Class-2 solid relays,but this structure will increase height of solid relays,so it is urgent to optimize internal structure of solid relays.According to requirements to technical index and volume restrictions of Class-2 solid relays,this thesis determines framework of main circuit,which is consisted of threshold circuit,anti-interference delay circuit,oscillation circuit,isolation circuit,rectification filter circuit,release circuit and output circuit.Anti-interference delay circuit is designed to prevent the input of pulses with interference of microsecond or millisecond level.Anti-interference delay circuit adopts structure of RC circuit,which can filter the transient interference signal within 5ms to ensure reliable operation of solid relay,and the anti-interference filtering time can be adjusted according to the requirements of users.In order to miniaturize Class-2 Solid relays,optimizing the double-layer structure,that the upper layer is a drive circuit and the lower layer is an output circuit.The high-power chip is mounted on the bottom plate of the base group for enhance thermal dissipation performance.The input drive using circuit board structure with a double-sided holes and metallized thick film,and reflow soldering with the printed board,in order to increase the fixing strength and reduce connection leads.The magnetic isolator is installed on the back of the printed board,installed via blind hole(sinking style)and designed staggered layer with the lower structure,which makes full use of the structure space and realizes miniaturization of product.Analyzing of the structure of Class-2 solid relays with double-layer structure,protected in association with characteristics of bare chips,and the process flow is optimized.According to the requirement to integral eutectic forming of the lower structure,a special high-temperature resistant fixture is designed to realize one-time eutectic welding and fixed forming.When welding the upper and lower structure together,the bare chip is protected integrally,clamps for welding and cleaning protection are designed to expose only the area to be welded,and the rest are protected and wrapped by clamps,so as to protect the bare chip.The baking of Class-2 solid relays is also deliberated.Two steps are adopted: 24 h vacuum bake out of the whole piece at 120?,48 h vacuum bake out at 120? before the enclosure are executed to meet the internal atmosphere control requirements,water vapor content is not more than 3000 ppm,oxygen content is not more than 2000 ppm,hydrogen content is not more than 4000 ppm and carbon dioxide content is not more than 5000 ppm.Analyzing sufficiently for the six abilities of Class-2 solid relays,including reliability,maintainability,safety,testability,supportability and environmental adaptability.Finally,a test plan is made according to technical indexes,and a full set of identific ation tests are done.And the test results comply with the requirements of technical indexes comprehensively.