Low-Energy Driven Ring-Opening Behavior of Benzocyclobutene Derivatives

It's urgent to develop benzocyclobutene(BCB)-based polymers with low curing temperature for temperature-sensitive applications such as liquid crystal displays(LCDs)and flexible electronics.Herein,the effect of substituents on the ring-opening behavior of BCB derivatives was investigated.The ring-opening activation energy barriers(ΔGA)of BCB derivatives with one or two substituents on the four-membered alkyl ring were systematically calculated using the B3LYP function.Both mono-and di-substituted BCBs adopted the conrotatory ring-opening process,obeying the Woodward-Hoffmann's Rules upon heating.The mono-/di-substituted BCBs exhibited 8.2%—69%lowerΔGA compared with BCB,attributed to the electronic effects of the substituents.Disubstituted BCBs with both electron-donating and electron-withdrawing groups,e.g.,1-NH_(2)-8-NO_(2)-BCB,demonstrated the lowestΔGA.In addition,BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules,and their ring-opening temperature can be decreased by 20℃ compared to the unsubstituted one,also consistent with our calculation results.This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next-generation BCB functional packaging materials with low ring-opening temperature.

A wafer-level 3D packaging structure with Benzocyclobutene as a dielectric for multichip module fabrication

A new wafer-level 3D packaging structure with Benzocyclobutene（BCB）as interlayer dielectrics（ILDs） for multichip module fabrication is proposed for application in the Ku-band wave.The packaging structure consists of two layers of BCB films and three layers of metallized films,in which the monolithic microwave IC（MMIC）,thin film resistors,striplines and microstrip lines are integrated.Wet etched cavities fabricated on the silicon substrate are used for mounting active and passive components.BCB layers cover the components and serve as ILDs for interconnections.Gold bumps are used as electric interconnections between different layers,which eliminates the need to prepare vias by costly dry etching and deposition processes.In order to get high-quality BCB films for the subsequent chemical mechanical planarization（CMP）and multilayer metallization processes,the BCB curing profile is optimized and the roughness of the BCB film after the CMP process is kept lower than 10 nm.The thermal,mechanical and electrical properties of the packaging structure are investigated.The thermal resistance can be controlled below 2℃/W.The average shear strength of the gold bumps on the BCB surface is around 70 N/mm^2.The performances of MMIC and interconnection structure at high frequencies are optimized and tested.The S-parameters curves of the packaged MMIC shift slightly showing perfect transmission character.The insertion loss change after the packaging process is less than 1 dB range at the operating frequency and the return loss is less than –8 dB from 10 to 15 GHz.

Synthesis and thermal polymerization of perylene bisimide containing benzocyclobutene groups

Fourfold benzocyclobutene-functionalized perylene bisimide（PBI 4） has been synthesized and its structure was characterized by FTIR,MS and NMR.PBI 4 can react either with itself,or the appropriate dienophiles to form the corresponding products under appropriate temperature.The polymer film obtained from the reaction of PBI 4 with methyl vinyl silicone rubber possessed excellent film forming properties including flatness.The optical properties of PBI 4 and polymer film obtained from the reaction of PBI 4 and methyl vinyl silicone rubber have been determined by UV/vis and fluorescence spectroscopy.

Heterogeneous integration of GaAs pHEMT and Si CMOS on the same chip

In this work,we demonstrate the technology of wafer-scale transistor-level heterogeneous integration of Ga As pseudomorphic high electron mobility transistors（p HEMTs） and Si complementary metal–oxide semiconductor（CMOS） on the same Silicon substrate.Ga As p HEMTs are vertical stacked at the top of the Si CMOS wafer using a wafer bonding technique,and the best alignment accuracy of 5 μm is obtained.As a circuit example,a wide band Ga As digital controlled switch is fabricated,which features the technologies of a digital control circuit in Si CMOS and a switch circuit in Ga As p HEMT,15% smaller than the area of normal Ga As and Si CMOS circuits.

Cycloaddition reactions of benzyne with olefins

Some novel cycloaddition reactions based on benzyne and olefins have been developed.These reactions were performed in the absence of a transition metal catalyst,and they displayed good yields.These cycloaddition reactions of benzyne with olefins provide effective routes for synthesizing benzocyclobutenes,biaryl compounds and 9,10-dihydrophenanthrene derivatives.