Preparation Of Halogen-Free Flame Retardant Epoxy Molding Compounds And Research On The Thermal Latent Behavior

Epoxy molding compounds(EMCs)is one of the important materials for integrated circuit(IC)chip packaging.With the continuous development of IC packaging towards miniaturization,thinningness,high-integration and high-input/output,the performance requirements for EMCs are also continuously improved.Conventional EMCs are facing many technical challenges in curability,moldability,melting flowability and reliability.The purpose of current work is to solve these technical problems by developing new types of thermally latent curing accelerators(TLCs)instead of the conventional curing accelerator,which usually has high reactivity and easy to induce the undesirable polymerization of epoxy resin and phenolic curing agent in the initial mixing stage.The derived EMCs might be endowed with good comprehensive performance.For this purpose,several works were carried out in the current paper.(1)Molecular design,synthesis and characterization of new types of TLCs.A series of tetraphenylphosphine-bisphenol charge transfer complex types of TLCs,including TLC-1~TLC-6 were first designed,synthesized and characterized.(2)Catalytic activity evaluation of new TLCs.The catalytic activity of the developed TLCs in the curing of epoxy/phenolic systems was evaluated by differential scanning calorimetry(DSC)and rheological analysis.And the thermal stability of TLCs was evaluated by thermogravimetric analysis(TGA).The measurements showed that TLC-1(tetraphenylphosphine-2,3-dihydroxyl naphthalene complex)and TLC-6(tetraphenylphosphine-hexafluorobisphenol A complex)exhibited the best combined properties,including good thermal latency and thermal stability.(3)Applications of new TLCs in EMC formulations.The behaiviors of the developed TLCs in the EMC preparations were investigated by using the developed TLCs were used as the curing accelerators,and the conventional triphenylphosphorus(TPP)accelerator as the reference.The results indicated that the use of TLCs can significantly improve the comprehensive performance of the EMCs.Taking TLC-1 as an example,the melting flowability of the EMC-1 using TLC-1 as the accelerator was apparently increased compared with the EMC-0 using TPP as the accelerator.The spiral flow length increased from 75 cm to 89 cm,the melting viscosity decreased from 19.55 Pa s to 9.54 Pa s,respectively.Meanwhile,the bonding force between the cured EMC and copper matrix increased from 652.4 N to 913.7 N and the flexural strength of the cured EMC increased from 90.2 MPa to 137.5 MPa,respectively.However,the EMC-1 showed a flame retardant grade of UL 94 V1,which is inferior to that of the EMC-0.(4)Applications of new TLCs in halogen-free flame retardant EMC formulations.Halogen-free flame retardant EMCs were prepared by using TLC-1 and TLC-6 as accelerators and phenoxyphosphazene oligomer(FP100)as the flame retardant,respectively.Experimental results showed that the flame retardant grade of EMC-a with TLC-1 can reach UL 94V0 grade by addition of only 0.3 wt% FP100,while for EMC-b with TLC-6,addition of 0.6 wt% FP100 was needed to achieve the UL 94V0 grade.