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Synthesis and characterisation of a nano-silver soldering paste obtained by NaBH4 reduction in presence of PVP

Dupont C., Sobota J., Głuchowski W., Wrona A.

Archives of Materials Science and Engineering

2013

Vol. 64, nr 2

237--242

Purpose: In this work, a new synthesis has been investigated to obtain a nano-silver soldering paste capable of sintering at low temperature. Design/methodology/approach: The nano-silver soldering paste has been obtained by chemical reduction, with sodium borohydride (NaBH4) in presence of polyvinylpyrrolidone (PVP). The paste has been used for bonding two Cu plates. The Cu-Ag-Cu joint was obtained by sintering the nano-silver paste at a temperature ranging from 200°C to 400°C, in air, under a normal load of 5 MPa. The shear strength of the joints has been measured. Findings: The Ag particles obtained by this method are spherical, with an average size of 100 nm which allow sintering at low temperature. A sintering temperature of 250°C is sufficient for bonding two copper plates and the paste with an Ag/PVP weight ratio of 2.45 offers the best results. However, a maximum shear strength of 51 N is measured which is lower than the literature reference for large Cu chips bonding. Research limitations/implications: Other Ag/PVP ratio should be investigated in order to minimise the presence of impurities introduced by the reactant. Investigations concerning the Cu surface treatment, for improving the shear strength of the bond, should also be realised. Practical implications: The nano-silver soldering paste cannot be applied, yet, in electronic industry. Further improvements are required. Originality/value: The synthesis of nano-silver soldering paste by chemical reduction with NaBH4 in presence of PVP can be realised in one-step, at room temperature, which is important to minimise the synthesis costs.

Mechanical and thermal properties of SiC : ceramics substrate interface

Kisiel R., Szczepański Z., Firek P., Guziewicz M., Krajewski A.

Elektronika : konstrukcje, technologie, zastosowania

2012

Vol. 53, nr 1

48-50

In this paper, we present the realization of assembly of SiC samples to DBC substrate (Direct Bonding Copper Substrate with 200 µm Gu metallization Au covered] by low-temperature sintering of micro scale Ag powder. In the preliminary experiments DBC test samples size 3 × 3 mm (in place of SiC die) were assembled to DBC substrate size 10 × 10 mm using following methods: a) sintering by Ag powder with Ag microparticles in air by applying temperature and pressure, b) sintering by Ag powder with Ag microparticles using temperature, pressure and high vacuum. Methods "a" and "b" permit to obtain very good adhesion range 8...10 MPa after sintering. However after ageing test at temperature 350°C in air the adhesion fall down dramatically. By increasing sintering temperature up to 500...550°C and sintering in vacuum range 1.3 Pa the adhesion is satisfactory. The results of these experiments will be presented in paper.

W artykule zaprezentowano proces realizacji montażu struktur SiC do podłoży DBC (ceramiki alundowej dwustronnie pokrytej warstwą Cu o grubości 200 µm) przy zastosowaniu niskotemperaturowego zgrzewania mikroproszkiem Ag. W badaniach wstępnych, zamiast struktur SiC zastosowano struktury DBC o wymiarach 3 × 3 mm montowane do podłoża DBC 10 × 10 mm (obie łączone części miary metalizację Au). W montażu wykorzystano mikroproszki Ag, a łączenie wykonywano przez: wygrzewanie w powietrzu pod naciskiem oraz przez wygrzewanie w próżni pod naciskiem. W obu metodach uzyskano dobrą adhezję tuż po łączeniu (z zakresu 8...10 MPa). Przeprowadzone próby starzeniowe w temperaturze 350°C wskazały, że adhezja próbek łączonych w powietrzu dramatycznie spada po 24 godzinach wygrzewania Natomiast adhezja próbek łączonych pod naciskiem w próżni 1.3 Pa w temperaturach z zakresu 500...550°C po procesach starzeniowych wtemperaturze 350°C przez kilkaset godzin jest dobra (powyżej 10 MPa).