Strain gage measurement History and experiences(,36页).ppt

* Strain gage instrument Supplier: Vishay Machine: system 5000 Model type: 5110A Features: measurement of strain force * 1. Stick sensors on the corners of U55 Steps of measurement 1/3 * 2. Place the tested board on ICT fixture Steps of measurement 2/3 * 3. Run the ICT test program and collect data from measurement instrument Steps of measurement 3/3 Bend degree and Spec. Unit: με Usage: With BGA mounted: * Above 900 High Risk 601 ~ 900 Acceptable Under 600 Excellent USI Specification: | Max. - Min. | 600 με Condition: All measured values at the same time * Gage The gage functions on the principle that when it undergoes strain, its electrical resistance changes. And if the relationship between the relative change in resistance ( ) and the strain ( ), (which is defined as the Gage Factor), is known, then the strain can be determined. * Strain Measurement * * Strain gage measurement History and experiences * History Product : Cordoba When : 03/20, 2002 Where : TW PD4 Symptom : Many power-up defects found at PFT CSA Cause : U55 (Northbridge) -- Intel Brookdale chip open Since 03/20 USI produced Cordoba-1N, the FPY rate of Cordoba product in PFT test stations is 70.4% (from 03/20 to 03/31). From the analysis, The proportion of U55 fail rate to PFT total fail boards is about 70%. After preliminary analysis and discussion, we suppose the pressure of ICT fixture may cause U55 (Brookdale) defect. As for the details of steps, conditions and results of trials will be described in the following paragraphs. * 1. First trial 1-1. Steps SMT-pass2 ICT 50 times PFT MFT X-Section Trials for root cause 1/12 * 1-2. Condition Original ICT fixture plate Trials for root cause 2/12 * 1-3. Results There is a gap Trials for root cause 3/12 * 1-4. Analysis ＊The solder joint in the PCB is well. ＊ There is a crack between the substrate and solder ball. ＊ The defect was found af