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40 The PCB Magazine • March 2014 manageable, thermal cycling and water absorp- tion coupons were not tested. However, HATS coupons were added to the panel design. The stackup used is shown in Figure 1. Material for test was supplied free of cost by each material supplier. Materials were given a code name for the study. Each material supplier will have cross reference to their material only. Table 1 gives the detail of the material proper- ties as published on technical data sheets. All material tested are rated by their manufacturers as lead-free assembly compatible material. Ma- terials ranged from a Dk of 3.7–4.7 and were in T g range of 1700–2100°C. All samples were produced using the same equipment and within a close time frame win- dow. No process abnormalities were seen dur- ing processing period. Test parameters selected are given below. HATS Preconditioning and Test Parameters Test Conditions • Six coupons for each material type to be cycled through 6x @ 260°C assy. simulation • Test temperatures for cycling to be -40°C temperature to 145°C, 15 minutes @ temperature and transition time is 30 seconds • Test cycles to be 1,000. Cycles or a change of 10% in resistance, whichever comes first • Testing done by Integrated Reliability Test Systems, Inc. (IRTS) HATS Test Analysis All coupons showed no signs of delamina- tion after preconditioning. During HATS test- ing all materials met the set criteria of 1,000 cycles without the exception of material 'RA' which had an average of 941 cycles for net 2 and 900 cycles for net 4. Material 'B' had an anomaly where there were spikes of 6% change in resistance between 600 and 800 cycles and after that the coupon went back to less than 0.2% change. Below are the charts for material 'A' (showing change in resistance for a typical good coupon), material 'RA' and material 'B'. BEHAVIOR OF MATERIALS IN THE MANUFACTURING ENVIRONMENT continues Figure 1: stackup for modified hdpug design (as shown in Figure 2). Figure 2: modified hdpug design.