Study On Co-firing Behavior Of Gold Conductor Paste With LTCC Green Tape

Gold conductor paste is one of the key raw materials for low temperature co-firing ceramic?LTCC?which is mainly used for producing high-reliability military electronic components.Its composition and properties greatly affect the electrical conductivity,solderability and co-firing compatibility of the sintered thick film.This paper focus on the research of preparation of gold powder as the functional phase of conductor paste,and sintering and co-firing properties with the green sheet.The research work has great theoretical significance and application value for promoting the performance of gold conductor paste used for LTCC.Aiming at the regulation of particle size and morphology,the effect of reaction conditions,such as the type of reductant,the type and amount of dispersant,the pH value and temperature of the reaction system,on the morphology and particle size of gold powder was investigated.The results show that the crystal structure and symmetry of the reductant affect the morphology of the gold powder.The particle size increased with the increaseing of the amount of dispersant,the pH of the reaction system,the temperature and the increase of the reaction system.It was found that the optim?m reaction condition was concentration of gold solution is 20g/L,concentration of ascorbic acid is 40g/L,weight ratio of dispersant to gold is 2,pH value of reductive system is 4,and the reaction temperature is 50?.Under this condition,spherical gold powder with average size 1.7?m was generated,the size distribution of the powder was0.8⁵?m,the surface area of the gold powders was 0.184m²/g,the tap density was more7.46g/cm³ and the loose density was 4.76g/cm³,the liquidity of the gold powder was good.The effects of the particle size,glass softening point and glass frit content on the sintering behavior of the gold powder were investigated.It is found that the sintering of gold powder begins when the temperature is between 300 to 400?.The degree of crystallization of the gold powder increased with the increasing of the gold particle size,and this increasing lowered the sintering activity,as well as lowered the initial sintering shrinkage temperature and sintering shrinkage rate.Addition of glass frit could change the sintering behavior of the gold powder,higher the softening point of the glass frit was,higher the initial sintering shrinkage temperature of the gold paste was.The gold powder with average size 1.7?m shrank sharply at 420?,will the shrinkage rate decreased with the softening point of the glass frit increasing,When increasing the amount of glass frit,the initial sintering shrinkage temperature of gold powder increased,sintering shrinkage rate increased,will the shrinkage decreased.In order to achieve the low shrinkage rate of gold conductor used for fill hole,two schemes were proposed as add high silica glass powder and SiO₂ powder plus low melting glass powder.The research showed that when the content of high silica glass powder increased,the initial sintering shrinkage temperature of gold powder did not change,will the sintering shrinkage rate changed little,but the sintering shrinkage rate decreased significantly.Adding the SiO₂ and low-melting glass,as the amount of SiO₂increased,the initial sintering shrinkage temperature of the gold did not cha nge,but the sintering shrinkage rate and the sintering shrinkage rate of the gold paste decreased,and the density after sintering was greater than adding the same amount of high silica glass.Through the research on the consistency,conductivity and welding performance of gold paste co-firing with the Dupont 951PT green sheet.The conductivity test results showed that the gold paste with high melting point glass is better than the gold paste with low melting point glass.The section of thick film after sintering showed that the glass and the gold powder mixed uniformly.When the solid content of the gold paste is88.5%,the co-firing of the filled hole gold paste and the green tape is good.The conductivity of the thick film made by the gold powder with the average diameter of1.7?m is much better than 1?m.When increasing the content of the glass powder,the resistance of the fired thick film is raising.The average diameter of the gold powder did not affect the resistance of the fired thick film.Adding Cu₂O cannot advance the welding performance of the gold paste.