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Development of surface insulation resistance measurements in electronic assemblies

Objective

The four project partners:
Lares Cozzi (Italy),
the National Microelectronics Research Centre (Ireland),
the National Physical Laboratory (UK) and
Siemens (Germany)
have developed a new SIR test.

The new test reflects the improvements made in modern instrumentation and the advances in flux technology. This three-year project has now been completed. The project has made a number of significant advances in the SIR method, which has been encapsulated in a new test method.roducti
State of Progress
The first major part of the experimental programme in WP2, 3 and 4 to develop a new SIR method produced some very exciting results which have very important implications for the practitioners of SIR testing. The project moved on to verify the method, via an internal intercomparison, in WP5, and this was successfully completed. The industrial demonstration and development of the test in WP6 was successfully completed. The work of WP6 evaluated the new SIR method with commercial fluxes following a range of industrial soldering processes. The test method was reviewed and modified as a result of WP6 and the tested in WP7. In WP7 boards prepared at Siemens and by the individual partners were tested by all the partners. The results from this intercomparison proved very successful, and completely validated the test method.

The project overall has come out with some fundamental changes to the existing SIR test. A major change in the method is with the SIR pattern itself, which is two interdigitated comb patterns used to measure the resistance across the circuit board service. The existing standard uses a pattern with a 500?m gap between the two combs, whereas this work has shown that a 200?m gap should be used. The test is sensitive to the change in gap, which does affect the response from the test. The finer gap has been selected, as it is more sensitive and, importantly, reflects current circuitry dimensions. The other major factor is the reduction of the test voltage from the existing 50 to 5 volts. This work has shown that using 5 volts is far more discriminating and difficult to pass. Again the majority of circuitry today is running voltages of around 5 volts and not 50 volts. Hence, these values are chosen in the new test and backed up with data.

The project partners organised a second workshop at a European conference in the UK. The workshop was again attended by flux suppliers and equipment manufacturers from across Europe, as well as assemblers of electronic equipment. The workshop was very effective at disseminating the research outputs. The participants were again keen to see a strong SIR standard that would be accepted internationally.
Work Programme
An interim eighth meeting was held in May at Siemens in Berlin to discuss results from WP6. A large amount of data was presented which had been analysed using a design of experiment approach. From this work a final method was defined for a final intercomparison between the partners. The intercomparison was very successfully carried out. A final meeting was held at the NMRC in Cork where the preparation of the final reports was discussed. Following the completion of the work a workshop was organised at a European conference in the UK.d

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

National Physical Laboratory (NPL)
Address
Queen's Road
TW11 0LW Teddington
United Kingdom

Participants (3)

Lares Cozzi SpA
Italy
Address
Via Roma 88-92
20037 Paderno Dugnano
National University of Ireland, Cork
Ireland
Address
Prospect Row
30 Cork
Siemens AG
Germany
Address
50,Siemensdam 50
13629 Berlin