Research On The Construction Of Conductive Patterns And The Soldering Interconnections In Printed Circuits

The current new generation of electronic circuit products tends to be more and more lightweight,integrated,and intelligent,which promotes the continuous iterative update of printed electronics technology.The additive construction of metal conductive patterns on any surface and the integrated interconnection of electronic devices is the key to meet the requirements of advanced packaging manufacturing.It is of great significance to develop the surface metallization processes on different substrates,as well as the law of soldering interconnection technology for the development of fully additive manufacturing technology in printed circuits.This work focuses on the technical characteristics of copper conductive pattern construction and soldering metallization interconnection in printed circuits.Studying the plasma modification mechanism of polyimide（PI）surface,and proposes a new method for catalytic deposition of copper conductive lines.Under laser soldering conditions,the surface soldering of different metal modified pads was explored.Besides,the influence of intermetallic compounds（Intermetallic Compounds,IMC）and voids in the soldering structure on the reliability of the interconnection area was studied.Specifically include the following.A new method for constructing copper conductive patterns by full addition on the modified PI surface was proposed.Infrared spectroscopy results show that the H·radicals in the H₂/Ar plasma could attack the imide structure,causing it to open the ring to generate a reductive aldehyde group（R-CHO）.XPS and SEM data further confirmed that after Ag（NH₃）₂⁺’s treatment,the newly formed R-CHO on the PI surface reacted with it to form a catalytically active silver element.Then,electroless copper plating was performed on this basis,and the thickness of the copper layer deposited after 50 min was about 4.20μm,it was combined with the PI and the bonding strength reached 5B level.The test showed that the copper layer crystallizes well,and surface was smooth,and the resistivity was as low as 3.83×10^-6Ω·cm.Besides,the anti-fatigue test and LED lighting experiment were passed,combined with graphic printing to prepare flexible conductive graphics with good electrical conductivity and mechanical properties.Based on laser soldering technology,the conditions of Sn-3Ag-0.5Cu（SAC305）solder on Cu,Sn,and ENIG metal-modified pads,and the differences in IMC growth behavior under isothermal aging condition tests were investigated.The results showed that the IMC layer formed by laser soldering is generally thin at the beginning,and the growth of the Cu₆Sn₅ layer will be accelerated under a long-term thermal environment.Compared with the ENIG pad,the IMC layer of the SAC305/Cu or Sn solder joints was easier to thicken,which because of the Ni layer inhibits the excessive diffusion of Cu-Sn atoms.The thrust test showed that the excessive growth of the IMC layer will weaken the bonding strength of the solder joints,and the solder joints formed by laser soldering enter the brittle failure stage later.For the common visible voids inside solder joints,the microscopic melting process and its influencing factors were analyzed.It was found that the smaller the particle size of the solder paste,the more flux content,and the higher the flux activity,the fewer voids formed by the solder layer.Using simulation tools to compare the transmission loss difference of the signal inside the transmission line with voids or no voids.Therefore,demonstrated the importance of reducing soldering voids to ensure the quality and signal transmission performance.