Analyzing SAC, SnAg, and Other Solder Bumps
Solder bumps (or solder balls) are tiny balls of solder used in integrated circuit packaging to provide contact between chip packaging/substrate and PCBs. Solder bumps are often used in BGA (ball grid array), CSP (chip scale packaging), flip chips and microBGAs. Traditionally, tin-lead (SnPb) has been the material of choice for solder bumps. However, restrictions on the use of lead in consumer electronics have driven the development of lead-free alternatives, including tin-silver (SnAg), tin-silver-copper (SAC), and gold-tin (AuSn).
Since the solder's mechanical properties require specific composition ranges, it is critical that manufacturers across the supply chain can precisely determine solder ball composition. Higher concentrations of silver can lead to intermetallic compounds that form large, brittle grains that can cause reliability issues; lower concentrations can increase the melting temperature and make re‑flow more difficult.
Additionally, solder bumps are becoming increasingly smaller to meet demands of current semiconductors and new technologies. The need to determine the composition of solder bumps is critical. While there are many methods to do some, many, such as cross-sectioning, atomic absorption (AA), and inductively coupled plasma (ICP) are destructive and impractical for individual bump inspection.
Bowman optics systems are specially equipped to measure composition of fine solder bumps with X-ray focus from 80µm down to 7.5µm FWHM spot size. These systems produce the small spot size required to measure small solder bumps without sacrificing total counts/flux, while increasing the sensitivity for targeted elements. The M and W series offer a dual camera optics systems that makes it easy to locate small bumps with table view, low-mag and high-mag camera with 140x magnification. Use the tableview to take an image of all samples on the measurement stage, then click on the image to automatically move to that point under the high-mag camera and pinpoint the exact measurement location.
Bowman XRF optics systems are versatile analytical tools for compositional analysis of small solder bumps, as well as plating thickness and composition and plating solution analysis. The reduced costs of time, personnel, and instrumentation required by other methods make Bowman XRF an excellent alternative.