European study casts doubts on current SIR testing
European study casts doubts on current SIR testing
Keywords NPL, Testing
A three year European collaborative project, partnered by NPL-National Physical Laboratory, UK; Siemens Research Centre, Berlin; NMRC-National Microelectronics Research Centre, Cork; and Lares Cozzi-a PCB manufacturer based in Milan; recently reported initial results of their SIR study at a meeting held on 8 March, in Berlin. Encouraged by the Project Officer in Brussels, the purpose of the meeting was to disseminate and discuss results with invited suppliers.
The aim of this project is to generate a new test method for SIR testing which is used in flux validation. The outcome of a limited study shows that we should be using finer pitches and lower voltages, which, if implemented, would generate SIR results that are an order of magnitude lower than using existing standards.
One of the participants, Siemens, says that this work is incredibly important and could result in the re-qualification of fluxes by both users and flux suppliers, Dr Chris Hunt at NPL recommends caution until further work is carried out. "Certainly, should this work prove conclusive, then it will have far reaching effects on our industry. A better, more accurate test method could certainly invalidate all existing test methods". So far the project has only included generic fluxes and further work is being carried out on commercial fluxes.
As well as the improved accuracy, other failures can be seen when one gets to fine pitch, e.g., SIR testing can also be speeded up from seven days to three days or less. The IPC Working Group have been made aware of these conclusions by Dr Hunt, in his presentation to them at the recent APEX Conference. IPC also has SIR testing under review and will draft a new standard for circulation. IPC and ISO are responsible for the global SIR testing standards.
Further information: Dr Chris Hunt, National Physical Laboratory. Tel: +44(0) 20 8943 6065; Fax: +44 (0) 20 8614 0429; E-mail: chris.hunt@npl.co.uk
