PC test does not reveal degradation. Thereby it can be concluded |
shift of the critical degradation from below the chip to the edges |
that bond failure will not be an issue for the new joint technology |
of the DCB. |
. XT. |
On the other hand, a further reduction of t on is expected to result |
The degradation pattern in the baseplate solder can be analyzed |
in significantly higher lifetime – independent from ΔT – as the |
by means of scanning acoustic microscopy( SAM). Figure 4 depicts |
stress in the substrate-to-baseplate solder is reduced significantly. |
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the results and underlines the impact of ton. For t on= 2 s, the degradation of the solder starts directly below the chip( Figure 4 a). Increasing t on from 2 to 5 s leads to a higher ΔT at the edges of the substrate-to-baseplate solder joint which in turn manifests itself in additional shear forces and a more dominant degradation at the edges compared to the beginning of the test( Figure 4 b). It has to be underlined, that the sample from Figure 4a afterwards reached more than 6∙106 cycles.
When ton is increased even further to 60 s, this effect becomes even more apparent as degradation is strongly accelerated at the edges of the baseplate-solder( Figure 4c). For this load, the degradation pattern bears strong resemblance to that obtained after passive thermal cycling. With the findings from it can be expected that a further increase of t on would lead to a complete
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Summary
In contrast to standard joining technology, the wire-bond related failure loses importance as bond failure can be excluded with. XT.
By increasing t on, the degradation of the baseplate solders joint shifts from below the chips toward the substrate ´ s edges and becomes the most prominent EOL mechanism. The. XT lifetime is still dependent on T vjmax and t on but is shifted to much higher numbers of cycling.
Based on this and in comparison to EOL mechanism of standard joining technologies, aluminum wire-bond and soft-soldering die attach, the. XT joining technology provides a major advantage with respect to lifetime. The described results of the lifetime research will be implemented in new lifetime models of the innovative. XT interconnect technologies.
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