水置换型缓蚀剂对印制电路板腐蚀行为的影响及作用机理

Effects of Water-displacing Corrosion Preventive Compound on Corrosion Behavior of Printed Circuit Board and Mechanism

目的研究Super CORR-A水置换型缓蚀剂对典型印制电路板腐蚀行为的影响及其作用机理。方法基于实测的舰载机电子设备舱环境数据,考虑印制电路板腐蚀敏感的湿热、盐雾和酸性大气等因素,编制了加速腐蚀试验环境谱,针对喷涂和未喷涂缓蚀剂的无铅喷锡印制电路板开展了14个周期的加速腐蚀试验,以宏观和微观腐蚀形貌、腐蚀损伤尺寸、接触电阻以及绝缘电阻为指标参数,表征了印制电路板腐蚀行为,分析了缓蚀剂对印制电路板腐蚀行为的影响,运用扫描Kelvin探针技术和红外光谱技术揭示了缓蚀剂腐蚀防护作用机理。结果未腐蚀时,缓蚀剂使得印制电路板接触电阻增大0.077%~0.224%,绝缘电阻降低1.99%~4.21%,缓蚀剂对其电气性能影响很小。对于未喷涂缓蚀剂的印制电路板,第3周期,呈典型局部腐蚀现象,焊盘有1/3的面积发生腐蚀;第5周期,发生明显的均匀腐蚀,焊盘80%的面积发生腐蚀;第14周期,基材全部失去原有的光泽度,焊盘完全腐蚀,表面覆盖有一层较厚的腐蚀产物,通孔被红棕色腐蚀产物覆盖。对于喷涂缓蚀剂的印制电路板,腐蚀程度明显较轻,第14周期,插接件出现轻微的腐蚀,内部附着有浅绿色腐蚀产物。第14周期,喷涂缓蚀剂的印制电路板焊盘最大腐蚀深度和宽度分别为未喷涂缓蚀剂试样的52.5%和24.3%。第0~5周期,喷涂和未喷涂缓蚀剂印制电路板接触电阻差值较小;第5~14周期,喷涂和未喷涂缓蚀剂的印制电路板接触电阻差值逐渐增大,第14周期时,缓蚀剂使得印制电路板接触电阻变化量降低了57.20%~82.87%。第14周期,喷涂缓蚀剂印制电路板绝缘电阻大于12.5 GΩ,仍具有较高的绝缘性能;而未喷涂缓蚀剂的印制电路板绝缘电阻变化幅度较大,降低了2个数量级,仅为0.66~1.75 GΩ,基本达到失效状态。结论Super CORR-A缓蚀剂对印制电路板初始电气性能的影响很小,缓蚀剂中含有多种官能团,具有良好的水置换能力、渗透能力和成膜能力,能有效抑制和减缓印制电路板的腐蚀,可以有效延长其使用寿命。

The work aims to analyze the effect and mechanism of Super CORR-A water-displacing corrosion preventive compound(CPC)on the corrosion behavior of typical printed circuit board.Based on the measured environmental data of electronic equipment cabin of shipboard aircraft,the environmental spectrum of accelerated corrosion test is compiled,considering the humidity,heat,salt fog and acid atmosphere sensitive to PCB corrosion.Fourteen cycles of accelerated corrosion tests are carried out for PCB which are not sprayed or sprayed with corrosion preventive compound.The corrosion behaviors of printed circuit boards are characterized by macroscopic and microscopic corrosion morphology,corrosion size,contact resistance and insulation resistance.The effects of corrosion preventive compound on the corrosion of printed circuit boards are analyzed.The mechanism of corrosion protection is revealed by scanning Kelvin probe technique and infrared spectroscopy.The results show that,without corrosion,the corrosion preventive compound increases the contact resistance of PCB by 0.075%~0.224%,and decreases the insulation resistance by 1.99%~4.12%.The corrosion inhibitor has little effect on its electrical performance.For the PCB without corrosion preventive compound,in the 3rd cycle,the typical local corrosion phenomenon occurs;in the 5th,80%of the pad area is corroded;in the 14th cycle,the original gloss of the substrate was lost,the pad is completed corroded.The surface is covered with a thick layer of corrosion,and the through-hole was covered by reddish brown corrosion products.For the PCB sprayed with corrosion preventive compound,the corrosion degree is obviously lighter.In the 14th cycle,the connector appears obvious corrosion,and there are light green corrosion products inside.In the 14th cycle,the maximum corrosion depth and width of PCB pad sprays with corrosion preventive compound are only 52.5%and 24.3%of that of the untreated one.In the 0~5th cycle,the contact resistance difference between spraying and not spraying corrosion preventive compound is small;in the 5th~14th cycle,the contact resistance difference between spraying and not spraying corrosion preventive compound gradually increases.And at the 14th cycle,the corrosion preventive compound makes the change of contact resistance of PCB decreases by 57.20%~82.87%.After the corrosion test,the insulation resistance of PCB sprayed with corrosion preventive compound remains above 12.5 GΩ,which still has good insulation performance.However,the insulation resistance of PCB without spraying corrosion preventive compound changed greatly.After 14th cycle of corrosion,the insulation resistance decreased by 2 orders of magnitude compared with the 0 cycle,being only 0.66~1.75 GΩ,and basically reached the failure state.Therefore,the Super CORR-A corrosion preventive compound has little effect on the initial electrical performance of PCB.The corrosion preventive compound contains many functional groups,and has good water displacement ability,permeability and film-forming ability.which can effectively inhibit and slow down the corrosion of PCB and effectively extend its service life.