| Recently,with the continuous development of electronic technology,military avionics equipment is also developing.In the past,the situation of relying on imports is gradually improving.The flow standard module developed in this paper is the key component of a key type of fuel control system in China,which mainly realizes the function of signal conversion.Because of the high requirements of performance,reliability and volume in the complex and harsh environment of the aircraft,the module has been dependent on imports in the past,so the independent research and development in this paper eliminates potential unsafe factors and embargo risks It has certain research value.The flow standard module developed in this paper mainly realizes two functions:one is to generate the oscillation signal to the external circuit as the carrier,the other is to demodulate and amplify the amplitude modulated signal of the external circuit and convert it into the standard square wave signal.In this study,the thick film hybrid integrated circuit technology is used to greatly reduce the area of the circuit board and improve the reliability of the module,so that the module has the characteristics of small size,high precision,high reliability,wide working temperature range,light weight and so on.Specifically including the following three aspects of work:Firstly,the design scheme of the whole circuit is determined according to the requirements and functions of the technical indexes.The whole circuit is divided into two parts according to its functions,the lower part is the oscillation circuit and the upper part is the detection amplification circuit,wherein the oscillation circuit is composed of the sine wave oscillation circuit and the voltage comparison circuit;the detection amplification circuit is composed of the signal amplification circuit,the detection circuit and the square wave conversion circuit Part composition.Through theoretical analysis and Multisim Simulation,the device parameters of each circuit are determined to meet the design requirements.According to the design specification of multilayer thick film,the layout of multilayer thick film substrate is designed,including the selection of the number of layers of substrate and the layout of each layer,the selection of device package,the design of thick film resistance,etc.The layout of multilayer thick film substrate is designed and fabricated.Secondly,the:flow standard module is processed and prepared.The main process steps include packaging structure design,substrate shell bonding process,component mounting process,cleaning process,gold wire bonding process,parallel seam welding process,etc.And the key optimization of metal bonding process,through the parameter test to select the appropriate bonding parameters,improve the bonding strength,so as to improve the overall reliability of the module.At the same time,the process complexity is low,meeting the requirements of mass production.Finally,the weight of the module is 9.34g and the size is 29.4mm x 19.4mm ×5.0mm.Finally,the electrical performance of the flow standard module is tested.The output amplitude of four pins is 29.0v,the frequency is 4.0khz square wave signal,the voltage error is less than± 0.3V at 25℃,± 1V at-55℃ and 125℃,the frequency error is less than± 0.04khz at 25℃,± 0.1 Okhz at-55℃ and 125℃;the input amplitude of 12 pins is 550mvpp,the internal frequency is 4kHz,and the external frequency is 3.3hz,When the modulation depth is 83%,the output amplitude of 6 pins is 5.0V and the duty cycle is 50%,the voltage error is less than±0.04V at 25℃,less than± 0.12v at-55℃ and 125℃,less than± 0.5%at 25℃,less than± 1%at-55℃ and 125℃.All of them are far less than the error requirements in the design index.At the same time,the reliability test of the module,after the test results are qualified,can fully adapt to the harsh airborne environment.The technical design and process research of the thick film hybrid integrated flow standard developed in this paper is expected to have certain reference value for the design of small size and high reliability related airborne equipment. |
