Electronics subjected to shock and vibration may experience strain rates of 1-100 sec -1 . High strain rate data is scarce for leadfree solders at strain rates in the range of 1-100 sec -1 , typical of drop-impact, shock and vibration.A new experimental method has been developed to achieve constant strain rate in the neighborhood of 1 to 100 sec -1 during the entire deformation history. SAC105 and SAC305, which are two of the widely used leadfree alloys, have been tested at strain rates of 10, 35, 50 and 75 per sec. Effect of aging on the high strain rate properties has also been quantified by subjecting the test specimen to thermal aging for varied periods of time at various temperatures. The leadfree solders have been exposed to constant temperatures of 25°C, 50°C, 75°C, 100°C and 125°C for 1 day, 30 days and 60 days prior to high strain-rate test. Full-field strain in the specimen has been measured using high speed imaging at frame rates up to 75,000 fps in combination with digital image correlation. The cross-head velocity has been measured prior-to, during, and after deformation to ensure the constancy of cross-head velocity. Experimental data for the unaged and the aged specimen has been fit to the non-linear Ramberg-Osgood model using two methods.

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Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted in proliferation of a wide variety of solder alloy compositions. Few of the popular tin-silver-copper alloys include Sn1Ag0.5Cu and Sn3Ag0.5Cu. The high strain rate properties of leadfree solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the Split Hopkinson Pressure Bar (SHPB) can be used for strain rates of 1000 per sec. However, measurement of materials at strain rates of 1–100 per sec which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. High speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, and SAC305 solders. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25°C and 125°C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of leadfree interconnects. Test assemblies has been fabricated and tested under JEDEC JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.