14.7.2Electricallyand thermally induced failure images
illustrates electrical failure images.
shows a failure image
significant for over-voltage and
one significant for over-current. The over-
voltage has caused a section of the chip metallisation in the cell field of the IGBT to
melt. While on the other hand, the over-current shows a fault pattern located directly
near the bond contactswhere largemoltenareas can be found.
Failures caused byover-voltage (a) over-current (b)
shows a fault image caused by high operating temperatures. Themelted chip
metallisation is clearly visible on the top. Further, solder has oozed out at the upper
edge of the chip. This became liquidwith the high operating temperatures andwas thus
able to protrude from under the chip.
Failures caused byhighoperating temperatures
14.8 Cosmicparticle radiation
The voltage blocking capability of IGBTs is a function of the junction temperature as
The higher the temperature, the higher the voltage blocking
capability. Accordingly, when designing the application, the operating point at low
temperatures requires special attention.
The second factor determining the voltage blocking capability is the cosmic radiation,
which was briefly mentioned in chapter
Since cosmic radiation is of great