Abstract
It is of great interest and challenge to simultaneously improve the storage stability and bond strength of one-component addition-cure liquid silicone rubber (OLSR) coating for electronic circuit board. In this work, we proposed an efficient approach to address this issue by incorporating both cyano-modification platinum catalyst (CN–PT) and urethane-containing poly(hydromethylsiloxane) (N-PHMS) into OLSR coating using a mechanical mixer. The CN–PT and N-PHMS were synthesized through thermal polymerization reaction and hydrosilylation reaction, respectively. The OLSR coating containing 0.3 phr CN–PT and 3 phr N-PHMS showed the best properties, with a tensile bond strength of 1.63 MPa, a storage period > 180 d at 25 °C, and a curing rate < 2 h at 80 °C. The salt-spray resistance and continuous power-on performance of OLSR coating were also improved, compared with pure OLSR coating. The synergism of CN–Pt and N-PHMS on the enhancement of both the storage stability and bond strength of OLSR coating was also explored. Our findings exhibited great potentials for fabricating OLSR coating with excellent long-term stable service performance including high storage stability and protective ability.
Highlights
Printed circuit boards (PCBs) are the heart of the communication and electronics industry
We proposed an efficient approach to address this issue by incorporating both cyano-modification platinum catalyst (CN-PT) and urethane-containing poly(hydromethylsiloxane) (N-PHMS) into one-component addition-cure liquid silicone rubber (OLSR) coating using a mechanical mixer
The cyanide group in acrylonitrile was grafted onto the platinum catalyst in order to improve the storage stability of the OLSR coating material
Summary
Printed circuit boards (PCBs) are the heart of the communication and electronics industry. One-component addition-cure silicone rubber (OLSR) coating has the advantages of low shrinkage, the ability to adjust reaction speed and conditions over a wide range, and the fact that no byproducts or degradation products are formed[14,15,16,17,18] It can obviously solve the problem caused by the released solvents and small molecules for solvent-based condensation-cure silicone rubber. Many functional groups including propargyl[20], amine[21], 1-phenylethylisocyanide[22], isocyanide[23] often caused the poison of the platinum catalysts Most of these thermal-latent hydrosilylation catalysts are used at a high curing temperature for addition-cure liquid silicone rubber (the curing temperature > 100 °C), and a low storage temperature (< 10 °C). The properties including storage stability, bond strength, surface morphology, protective performance of the OLSR coating will be tested to evaluate the advantages of this combination designed OLSR coating for PCBs
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