X-rays vs. Cross Sections to Measure Voids

Authored By:

Transcript

As complex electronic assemblies become faster and faster, power with associated heat dissipation, signal integrity and reliability become more important than ever.

Solder joint voiding can potentially impact all of these. With cost pressures on companies producing these types of products, it's important to be able to properly diagnose and characterize voiding in a non-destructive fashion.

Proper characterization allows for adequate troubleshooting and process development needed to minimize or eliminate voiding. In addition, non-destructive void analysis can be used in failure analysis cases.

The resolution of x-ray tools has continued to advance along with the software required for automated analysis. Use of these tools has allowed identification and measurements of the voids in solder joints.

Software has allowed for automated inspection of solder joints to quickly identify and measure up 100 % of the solder joints per component and per assembly in a timely manner.

While many improvements have been made in these tools, smaller voids and true position of these voids has been difficult to see without actual cross sectioning.

Now with the latest advancements in X-Ray technology, a full high resolution 3D image is available using Cat Scan technology. Cat Scan technology allows for infinite cross sectioning in a non-destructive fashion.

The first objective of this work was to correlate the most common X-Ray technologies used by the electronics industry. Each technology was correlated, not only to the newest Cat Scan technology, but also to actual cross sections on a variety of void examples.

The second objective of this work was to identify and characterize a variety of voids from incoming components through the SMT reflow process. Incoming components identified with solder voids were subjected to a variety of reflow profiles to determine what happens to them relative to size and position.

Images and measurements were taken before and after reflow using all the traditional X-Ray tools along with Cat Scan. After all imaging was completed; actual cross sections were taken for comparison. In addition, components with incoming voids were subjected to reflow under vacuum in an attempt to remove the voids prior to assembly

So what were the conclusions?

1. 3D AXI is necessary to screen out significant quantities of components as data points, prior to further characterization.

2. A combination of available void detection technologies are needed for complete characterization of process and components, especially for increased complexity.

3. PCB and component design, reflow profile parameters ,as well as chemistry can all affect growth and positioning of voids.

4. High resolution Cat Scan imaging allows for a complete analysis of components before and after assembly in non-destructive manner.

And 5. A clear joint industry specification needs to be considered to create better linkage between component manufacturing and PCB assembly and inspection.

Summary

Conclusions

Comments