Study On Spectral Analysis And Preparation Of UV Cured Surface Coating For Fingerprint Module

With the vigorous development of the digital economy,fingerprint recognition technology has been widely used in fields such as mobile phones,tablets,secure access control door locks,and mobile payments.The currently used module assembly process uses high-temperature solder to weld the chip and the FPC board together,but the high temperature of wave-soldering(245℃)will cause cracks in the surface coating,affect the appearance and using effect.The existing fingerprint recognition module surface coating has insufficient hardness and high temperature resistance.In order to develop coating glue with better performance,it was commissioned by a company in Guangdong to carry out spectral analysis on a module surface coating in use.Then understand its basic composition and structure,and design,compound and improve on this basis.First,the existing unknown UV-curable coating was comprehensively analyzed by infrared spectroscopy(FT-IR),thermal pyrolysis gas chromatography mass spectrometry(Py-GC/MS)and nuclear magnetic resonance spectroscopy(NMR)and other methods.The results show that the unknown sample contains reactive diluent monomers isobornene acrylate(IBOA),pentaerythritol tetraacrylate(PET4A),photoinitiator1-hydroxycyclohexyl phenyl ketone(184)and polyurethane acrylate prepolymer.The isobornyl acrylate in the sample was quantitatively analyzed by ~1HNMR,and the relative content of it was about 25%.Secondly,on the basis of spectral analysis,with urethane acrylate resin as the main body,the influence of the type and content of photoinitiator,the type and content of diluent,and the effect of oxygen inhibition on the UV curing process were studied.Experiments show that the cleavage free radical initiator 1-hydroxycyclohexyl phenyl ketone(184)and the hydrogen abstraction free radical initiator benzophenone(BP)are used in a ratio of 1:1,and the system is at a concentration of 4%.The light curing reaction rate is the fastest.The greater the functionality of the reactive diluent monomer and the more reactive groups in the system,the easier the photo-curing reaction will proceed.The curing rate of the system is the fastest when its dosage is 50%.Finally,based on the results of sample analysis and photo-curing reaction research,the UV curing coating formula for fingerprint modules was designed and optimized.The variable factors in the formulation were investigated:the influence of diluting monomer,prepolymer type and content,leveling agent,etc.on the coating performance.The tensile shear strength,viscosity,tape abrasion resistance,hardness,and wave solder resistance temperature of the surface coating adhesive were characterized by universal tensile machine,rotational viscometer,paper tape abrasion tester and other methods.The optimized basic formula is:30%polyurethane acrylate resin,70%reactive diluting monomer,4%photoinitiator,and 0.5%leveling agent.The on-site coating test was done in a company in Guangdong,Conducted on-site coating test in a company in Guangdong.The coating hardness is 3H/1000g,the adhesion is level 1,and the coating is baked at a high temperature of 260℃for 10 minutes,the appearance of the coating is good.The abrasion test of the paper tape is more than 200 cycles.These can satisfy the process requirements.