Research On Solder Paste Printing And Detection Methods For Military Electronic Products

In the production of military electronic products,it is often faced with the mixed assembly of electronic components with greatly different package sizes.Therefore,how to ensure that the solder paste coating amount of all components meets the requirements has become an urgent issue for military units.This article addresses this problem through two scenarios: The first solution is that selecting the thickness of the stencil for mature and mass-produced military products to solve the problem.And proposing a method for setting the solder paste detection parameters of fine pin package components.The second solution is aimed at experimental,small-volume production of military industrial products,which solves this problem in the way of solder paste coating.And designing a solder paste spray printing shape that can reduce the generation of solder beads.The article first briefly introduced the development history of surface mount technology,performance parameters of test equipment and preparation of test materials.Designed the experimental process flow,including printing process,inspection process,placement process and reflow soldering process,analyzed and controlled key parameters in each process.The process of optimizing the reflow temperature curve of Sn62Pb36Ag2 solder paste in the reflow soldering process is emphasized.The SPSS software is used to analyze the test data to obtain the relationship between the PWI value(Process Window Index)and the temperature in each temperature zone.Then the article describes the test contents of solder paste printing and solder jetting printing test.Comparing the relevant standards for reflow solder joint inspection in the IPC and the National Military Standard,the specific requirements of solder joint inspection for current military units are described.In the solder paste printing test,the solder joints of the test circuit board printed with 8 thicknesses of stencils were tested according to military requirements,and the thickness range of stencils suitable for printing of various packaging components was given.Based on this,the exploration of the SPI solder paste detection parameter threshold of the LQFP32 package components.In the solder jetting printing test,the solder joints of the test circuit board printed with different volume parameters are tested according to the military requirements,and the optimal volume parameters suitable for the printing of various packaging components are given.And optimizing the print shape of RC elements that their Encapsulations are 0805 and larger.Finally,the test circuit board was subjected to temperature cycle experiments and vibrationexperiments.X-RAY inspection of the BGA package components after the experiment,And metallographic tests on the solder joints of BGA and QFP package components,The reliability of the military electronics products produced by Sn62Pb36Ag2 solder paste was verified by analyzing the voids of the BGA solder joints and the topography of the solder joint profiles of BGA and QFP package components.