Global Sourcing Spotlight: Tariffs—The New Reality
Knocking Down the Bone Pile: Gold Mitigation for Class 2 Electronics
Punching Out: Your Financial Preparation for a Sale
Evaluating the Tripod as an Alternative Cross-Sectioning Method
February 25, 2016 | Steve Ring, Foresite Inc.Estimated reading time: 1 minute
The electronics industry has been using the epoxy puck to process the vast majority of electronics micro-sections since the 1970s. Not much has changed in that cross-sectioning method, which is now used for precision micro-sections of PCBs, PCBAs, and device packages.
Encapsulating samples in a cylindrical "puck," using either thermal-cure or room-temperature-cure epoxies, has been the standard operating procedure for cross-sectioning electronic samples for years. However, this method can be somewhat limiting in the preparation of specimens to be analyzed where there is a need for a specific angle of attack and/or a requirement to stay parallel to a datum plane. Additional disadvantages or weaknesses in this method also exist.
One particularly advantageous alternative is the tripod method. Cross-sectioning using a tripod micro-section fixture dates back to the late 1980s, but has primarily been used for silicon wafer analysis. Considering the degree of control needed for wafer and die cross-sectioning, we wanted to bring the advantages of this method to our analysis of SMT and PCB sections. Those advantages include the following:
- Easier specimen positioning and repositioning, if desired
- Reduction of bulk material (epoxy), resulting in the following:
- A faster rate of removal/less processing time
- Less grit and polish consumption
- Less removed material (less waste and reduced potential to affect the specimen)
- Minimal light distortion
- Advantages during SEM imaging
Although this manual method limits the size of the specimen and requires dedicated fixtures throughout the analysis, we find that using the tripod fixtures, in most instances, proves beneficial.
Other cross-sectioning considerations
For other cross-sectioning considerations, Foresite lead investigator Manuel Solis presented a technical article titled "Alternative Methods for Cross-Sectioning of SMT and PCB-Related Architectures" at last year's SMTA International conference. In that paper, he outlined more details on cross-sectioning techniques, including hints and recommendations related to:
- Bulk material removal
- Sample encapsulation (pre, micro and mini)
- Handling of flux residues and conformal coatings
- Grinding and lapping
- Sample cleaning
- SEM imaging
Share on:
Suggested Items
Residues Can Cause Low Voltage Electronics to Ignite
07/20/2015 | Steve Ring, Foresite Inc.This article dispels the myth that low-power devices such as remote controls have insufficient energy to be a source of ignition. It also discusses why leakage current, even in low voltage/low power applications, can be sufficient to eventually ignite proximate fuel and lead to sustained fire in PCBA surfaces.