Decrease in the camber degree of Au/ceramic co-fired structure for LTCC technology
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Decrease in the camber degree of Au/ceramic co‑fired structure for LTCC technology Tingnan Yan1 · Xingyu Chen1 · Weijun Zhang1 · Fenglin Wang1 · Zhuofeng Liu1 · Kaili Zhang1 Received: 31 March 2020 / Accepted: 17 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract To relieve the camber of Au/ceramic co-fired structure, investigation on the sintering of gold paste with different constituent material properties was performed in this study. The sintering initial temperature of gold paste was correlated with the gold particle size, the glass softening point and the glass content closely. By adjusted the gold paste sintering shrinkage behaviour the camber evolutions were obviously changed, including the camber direction and the camber degree. When glass content in gold paste was 3 wt% and the softening point was 730 °C, the Au/ceramic co-fired structure exhibited the minimum camber, of which the ht/ho value was 0.96. The results of this work have shown the relationship between the camber evolution of Au/ceramic structure and the sintering shrinkage behaviour of gold paste, which would give an avenue to solve camber in the LTCC application.
1 Introduction The microelectronic packages are exhibiting the development tendencies of three-dimensional (3D) high density integration, high signal-transmission speed and excellent reliability [1]. Low temperature cofired ceramics (LTCC) meet above-mentioned demands due to its own excellent dielectric properties, well cofiring with copper, silver and gold circuit and 3D packaging characteristics [2–7]. Considering the printed fine circuits and embedded small electronic components in the LTCC modules, the size and shape of the products must be accurately controlled during the production process to maintain their availability. However, camber is one of the most common defects that may occur during the sintering process, and will damage the effort in controlling the size and shape of LTCC module. The mismatched sintering shrinkage rate between metal paste circuit and green tapes will lead to the camber in metal/ceramic co-fired structure [8, 9]. Currently, engineering approach, such as constrained sintering, is often applied to minimize the camber of metal/ceramic co-fired structure * Xingyu Chen [email protected] * Weijun Zhang [email protected] 1
College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
[10–13]. During the constrained sintering process, cofiring defects like cracks, porosity and delamination can be observed because of the tensile stress of ceramic substrate caused by constrained sintering [14, 15]. It is clear that constrained sintering is only a flawed method to relieve the camber of metal/ceramic co-fired structure during cofiring. One of the better methods to solve the camber problem of Au/ceramic co-fired structure is to modulate the sintering shrinkage behaviour of CaO–B2O3–SiO2 (CBS) green tapes and gold paste circuit. However, the narrow sintering window and h
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