Consider a ceramic package where the solder glass used has the following properties; E(g) = 0.7 × 10^6 kg/cm², v(g) = 0.27, α(g) = 6.8 × 10^-6 °C^-1. Similarly, for the alumina ceramic, E(c) = 3.5 × 10^6 kg/cm², v(c) = 0.25, α(c) = 7.2 × 10^-6 °C^-1. If the seal processing temperature is 450°C,

Question

Consider a ceramic package where the solder glass used has the following properties; [latex]E(g) = 0.7 × 10^6 kg/cm^2 , v(g) = 0.27, α(g) = 6.8 × 10^{-6} °C^{-1}[/latex]. Similarly, for the alumina ceramic, [latex]E(c) = 3.5 × 10^6 kg/cm^2 , v(c) = 0.25, α(c) = 7.2 × 10^{-6} °C^{-1}[/latex]. If the seal processing temperature is 450°C , what stress can be expected in the glass at 25 °C?

Accepted Answer

It is assumed that all stresses are relieved at 450°C. Therefore, by Eqn (8.25)

[latex]\sigma=E(g)[\alpha(c)-\alpha(g)](T-T_{o})[/latex] (8.25)

the thermal stress produced in the glass at 25 °C is [latex]\sigma =0.7 imes 10^6/(1-0.27)[7.2 imes 10^{-6}-6.8 imes 10^{-6}](450-25)=163kg/cm^2[/latex]. This value should be compared to the [latex]5500 kg/cm^2[/latex] compressive (fracture) strength of the glass. The undesirable tensile stress that develops underscores the need for high-toughness solder glasses.

Question 8.1: Consider a ceramic package where the solder glass used has t...