Interaction Effect of Voids and Standoff Height on Thermomechanical Durability of BGA Solder Joints

Abstract

This paper documents simulation studies on the interactive effect of standoff height and void volume on the thermomechanical durability of ball-grid-array solder joints using a 3-D viscoplastic finite element analysis. Surface Evolver software was used to find the optimized shape of the solder joints and standoff height by minimizing the surface energy as voids with different sizes were placed in solder balls. A global-local modeling approach was then utilized to model the thermomechanical durability of voided solder joints. Void-area-fraction ranges of 14%-40% were analyzed. A nonmonotonic behavior of durability versus void area fraction was observed. The results showed that, if the void is completely inside the solder ball and has no interface with the boundaries of the joint, it does not have a detrimental effect and even improves the durability as the void size increases. However, voids located at the interface of the solder joint and copper pads were found very detrimental to durability. Factors such as load bearing area, stress concentration factor, and overall compliance of the structure were found responsible for the nonmonotonic behavior of the joints. An analytical micromechanics approach was used to calculate the compliance of the structure, and a nonmonotonic trend in phase with the durability trend was observed. The stress concentration factor also showed the same nonmonotonic trend. The rise of these two factors for the void interfacing with copper pads in addition to the decreased-load-bearing-area effect resulted in a drastic decrease in durability.

Demonstration of electrical connectivity between self-assembled structures

“…44 It has previously been used to simulate the folding process for hollow and patterned polyhedra that rely on liquid solder hinges 45 and has been applied to predict the standoff height of ball-grid array solder joints. 46 In our work, surface tension and gravity were modeled to determine the ultimate shape of the pyramid. In determining the surface energy, one takes into account surface tension and gravitational forces.…”

Effect of component standoff height on thermo-mechanical reliability of ball grid array (BGA) solder joints operating in high-temperature ambient

“…Factors which include geometric parameters and operating ambient conditions have been widely reported by [1][2][3][4][5][6] to interact and influence the damage mechanism of the solder joints. Based on this report, the authors are motivated to harness this knowledge and use change in component standoff height (CSH) to improve the thermo-mechanical reliability of ball grid array (BGA) solder joints which are usually subjected to thermal cycling.…”

Polymer Core BGA Stress Analysis at Minimal Vertical Loading

“…Ball grid array is an interconnection method used in the semiconductor industry to produce miniature electronic devices [1].The BGA is a form of solder ball. The functions of these solder balls are to conduct electrical signals and also power supply from the integrated circuit to the printed circuit board [2].Ball grid array and flip chip technologies have many advantages in terms of smaller form factors and better thermal and electrical performance [3].Reliability of the solder balls are being improved for its best performance and also to withstand frequent usage of the device [4]. At industries, the expectation of a device have longer life cycle upon high usage and working on critical environment is becoming high.…”