Dynamic materials testing and modeling of solder interconnects

Abstract

Accurate material models are necessary to obtain meaningful results in computational simulation. The results of materials testing and the process of developing a material model for solder under impact loading are presented in this paper. The material model will be used in the simulation of electronic packages under drop impacts. As such, it is necessary to incorporate the effects of strain rate sensitivity in the model. Dynamic materials properties of Sn63Pb37 solder were obtained by testing the solder using the Split Hopkinson Prt:ssure Bars. The accuracy of the material models was evduated by subjecting single solder balls to impulsive loads on the SHPB and comparing the test results with finite element simulation.During Split Hopkinson Pressure Bar tests on cylindrical solder (eutectic) specimens, it was found that the stress to achieve 2% strain increases from 79 to 112 MPa when the strain rate increased from 450 to 2720 s-'. Examination of the fractured surfaces showed that there is a transition from ductile to brittle fracture as strain rate is increased. SHPB tests on single solder balls also showed that the stiffhess of the solder balls is strongly dependent on rates of deformation. For example, when solder balls (eutectic) of diameter 0.76 mm were compressed at a rate of 2.35 d s , a force of 36 N was required to achieve 0.2 mm compression. For a deformation rat(: of 8.83 d s , the force increased to 50 N to achieve the same compression. 0*7803-836!L6/04/$20.00 02004 IEEE I * COLOR I ~~ Your accompanying CD-ROM contains a version of this paper with color images.httpYhwv.cpmt.org/proceedings/

Reliability of lead-free interconnections under consecutive thermal and mechanical loadings

“…This is due to the increased strength of tin-rich solder alloys by strain-rate harden-ing. 11,12,[17][18][19] Therefore, good mechanical properties of intermetallic compounds are especially important, when interconnections are subjected to mechanical shocks.…”

Board‐Level Reliability of Lead‐Free Solder under Mechanical Shock and Vibration Loads

“…Many different high-strain-rate methods ranging from the classical split Hopkinson pressure bar [34][35][36][37] and miniature Charpy testers [38][39][40] for single solder balls to sophisticated drop testers for populated component boards have been proposed for studying the impact reliability electrical components and assemblies (see Fig. 2).…”

“…When the component boards are loaded with a shock impulse, several natural bending modes are excited simultaneously and, as a consequence of their simultaneous vibration, the bending of test assemblies can be highly complex and the mechanical analysis by the Figure 2 Some high-strain-rate methods developed for shock impact testing of surface mount devices and assemblies: (a) split Hopkinson pressure bar [34][35][36][37]; (b) miniature Charpy test [38][39][40]; (c) single bump shear or pull test [38][39][40][41][42][43][44][45][46][47][48][49]; (d ) die/package shear [51]; (e) die/package double shear [52]. finite element method (FEM) can become challenging.…”

Dynamic Mechanical Properties and Microstructural Studies of Lead‐Free Solders in Electronic Packaging

“…Wang et al [25] and Siviour et al [35] obtained strain rates reaching up to a maximum of 3000 sec −1 from SHPB experiments on solder material. However, numerical simulation by Ong [59] shows that certain parts of the solder balls will experience higher strain rates (close to 10,000 sec −1 ) when the solder balls are compressed at a deformation rate of approximately 5 m/sec. Different striker bar velocities ranging from 5 to 15 m/sec were used with the different specimen lengths to attain strain rates ranging from 10 2 to 10 4 sec −1 .…”