Leading expert in reliability of solder joints Jean-Paul Clech has presented a webinar on knowledge gaps in lead-free soldering reliability technology at the IPC MidWest in September.

He highlights a list of knowledge gaps in reliability modelling and testing including lack of data and weaknesses in some models.

The continuing proliferation of new lead-free alloys makes this situation more complex. For each new alloy a new dataset is required, There is a particular lack of thermal cycling data. The new alloys have different microstrcutures and intermetalics. Data on interface behaviour is required as well as bulk properties.

Investment in reliability studies should be up-front in any new development and not when there have already been expensive field failures. Development has been too much on a 'trial and error' basis. A more fundamental understanding would have reduced the costs of lead-free soldering implementation.

There has been too much emphasis on increased strength of lead-free solders. In fact it is ductility that is important. Solders should absorb stresses and strains and not resist.

Jean-Paul describes knowledge gaps in detail including lack of cold temperature creep data, lack of low stress data, hysteresis loops, CTE measurement and development of thermal cycling models, for example.

There are some interesting comments and questions from the audience at the end of the presentation.

The webinar is available from the IPC website on the reference link below.