Electroneutral Quaternization/Sulfosuccination for Alleviating the Adverse Effect of Paste Aging on the Properties of Corn Starch Film

For the purpose of alleviating the adverse effect of paste aging on the properties of corn starch film, a series of electroneutrally quaternized/sulfosuccinylated starches（EQSS） with different degrees of substitution（DS） were synthesized via the quaternization/sulfosuccination of acid-thinned corn starch（ATS） by varying the amounts of N-（3-chloro-2-hydroxypropl） trimethylammonium chloride, maleic anhydride, and sodium hydrogen sulfite. The influence of paste aging on the properties of starch film cast from heat-induced starch paste was investigated and the properties were explored in terms of tensile strength, elongation, work at break, degree of crystallinity, and flex-fatigue resistance. The experimental results showed that the paste ageing generated adverse influence on the elongation, work at break, and flex-fatigue resistance of starch film. Further experiments showed that electroneutral quaternization/sulfosuccination of starch were able to alleviate the negative effect of paste ageing on the elongation, work at break, and flex-fatigue resistance, thereby obviously enhancing the elongation, work at break and flex-fatigue resistance, and thus reducing the drawback of brittleness. The enhancement depended on the amounts of the substituents introduced. With the increase in DS value, the elongation and work at break as well as flex-fatigue resistance continuously rose, whereas the tensile strength gradually reduced.

Interfacial enhancement of Ag and Cu particles sintering using(111)-oriented nanotwinned Cu as substrate for die-attachment

The electroplated(111)-oriented nanotwinned-Cu(nt-Cu) film was utilized as substrate for Ag and Cu sinter joining to improve the weak interface connection between the metal paste and the substrate.It was found that both Cu and Ag sinter joints using(111)-oriented nt-Cu film exhibited a higher bonding strength than that using traditional random-oriented Cu film.Especially,the joints sintered with Cu paste on(111)-oriented nt-Cu film possessed a higher bonding strength of 53.7 MPa at the sintering condition of 300 °C,0.4 MPa in N2 atmosphere,compared to that on random-oriented Cu film with a value of 31.3 MPa.The results show that as metal substrate layer,the(111)-oriented nt-Cu film can improve the connection performance of Ag and Cu sinter joints,which could further promote their application in dieattachment technology for the next-generation power semiconductors.

Development of anti-oxidation Ag salt paste for large-area(35×35 mm^(2))Cu-Cu bonding with ultra-high bonding strength

In this paper,by proposing a novel and low-cost Ag salt paste,a robustly and large-area(35×35 mm^(2))bare Cu to Cu bonding was realized under a low sintering pressure of 0.8 MPa and a low sintering temperature of 300℃ in air atmospheric conditions.The relationship between the bonding strength and microstructure changes of sintered Ag under various bonding conditions was investigated in detail.The large-area bonded plate exhibits low porosity about 10%and low percentage of voids,which result in ultra-high bonding strength over 58 MPa.More importantly,the introduction of reducing agent formic acid(CH_(2)O_(2))and the low porosity successfully improve the anti-oxidation of novel Ag salt paste during sintering process,result in pure Cu-Ag-Cu bonding.The cross-section of the Ag joints was obtained to explain the bonding pattern,in which Cu was oxidized only at the edge of the sintering interface,and no Cu oxide generated in middle bonding section.The development of novel Ag salt paste successfully addresses the energy-intensive process and low bonding strength faced by large-scale sintering,which greatly promotes the high-temperature applications of power device.