Stencil Printing Yield Improvements
Overcome Nodules and Scratches on Wire Bondable Plating on PCBs
Solder Paste Selection for Bottom Termination Components Attach
Jetting Solder Paste Opens Up New Possibilities
Advances Autonomous Driving V2X Technologies
Surface Insulation Resistance of No-Clean Flux Residues
Jetting Conductive Adhesives with Silver Coated Polymer Particles
Residues on Probing PCBAS-Consistent Connections Across No-Clean Fluxes
Latest Industry News
Applying Strategic Sourcing Principles to Modern Procurement
Should You Trust Apple's New Blood Oxygen Sensor?
Cobalt demand for 5G technology to challenge electric vehicles
S. Korea to launch supercomputer for biotechnology in 2023
China needs first mover advantage in digital currency race
Top 10 Digital Transformation Trends For 2021
Chinese leaders split over releasing blacklist of U.S. companies
It's getting harder for tech companies to bridge the US-China divide

Engineered Tin-Copper Alloys in Selective Soldering

Engineered Tin-Copper Alloys in Selective Soldering
The performance with one alloy under design conditions that make soldering difficult demonstrate the need to evaluate the performance differences.
Production Floor


Authored By:

Jason Fullerton and Chris Colindres
Alpha Assembly Solutions
South Plainfield, NJ, USA


This paper details an experiment that compares the hole fill performance of two engineered tin-copper alloys in a selective soldering process. The test vehicle design incorporates features that are optimized for the selective soldering process. Two experiments are performed - one uses no preheat and no inner layer connections at the hole and the second uses preheat and thermally challenging inner layer connections. Hole fill is measured via X-ray software algorithm and the relative performance of each alloy is compared. The performance advantage observed with one alloy under design conditions that make soldering difficult demonstrate the need to evaluate the performance differences of even similar alloys due to the effects of small additives to standard alloys.


Soldering Without Preheat
This experiment demonstrated that neither alloy was able to produce acceptable hole fill performance under the conditions tested in this experiment. Further investigation would be necessary to determine the main factor(s) that need to be optimized to ensure acceptable hole fill performance under these conditions, including the control factors of solder pot temperature and contact time but also potentially including aspects that are out of scope for the project as planned (flux, PCB finish, alternate alloys).

Selective Soldering With Preheat
The contour plots comparing the two alloys demonstrate a significant performance advantage when selective soldering with the SnCuBiNi+P alloy over the SnCuNi+Ge alloy under conditions that are thermally challenging.

With 1.6 mm thick boards, the performance of SnCuBiNi+P was consistent across a wide range of solder contact times. For the tested range of 280 Celsius - 310 Celsius solder temperature and 2.0 - 5.0 solder contact seconds, any preheat temperature between 70 Celsius - 100 Celsius is expected to provide complete hole fill. Even the best results for the SnCuNi+Ge alloy, at the highest solder temperature of 310 Celsius, was only expected to provide complete hole fill at preheat temperatures between 70 Celsius - 90 Celsius.

In addition, the SnCuBiNi+P alloy was predicted to provide acceptable hole fill at consistently higher preheat temperatures than the SnCuNi+Ge alloy under similar solder temperature conditions, particularly with low solder contact times.

The 2.4 mm thick board results, as expected, showed a reduced window of conditions that are predicted to provide acceptable hole fill results. With 2.4 mm thick boards, the SnCuBiNi+P alloy had a wider range of conditions that are expected to produce acceptable hole fill results when compared to the SnCuNi+Ge alloy under all solder temperature conditions tested.

For all solder pot temperature conditions tested, the SnCuBiNi+P alloy was predicted to result in acceptable hole fill when solder contact time was between 3.0 - 5.0 seconds and preheat temperature was between 70 Celsius - 100 Celsius. With the SnCuNi+Ge alloy, the only conditions that resulted in acceptable hole fill over all solder temperatures tested are those with preheat temperatures between 70 Celsius - 80 Celsius and solder contact time between 4.0 - 5.0 seconds.

Initially Published in the SMTA Proceedings


No comments have been submitted to date.

Submit A Comment

Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name

Your Company
Your E-mail

Your Country
Your Comments

Board Talk
Solder Pallets With Titanium Inserts - Yes/No?
What Rate is World Class for SMT Machines?
Selective Solder Pot Temperatures
Top Side Reflow Causing Solder Balls
Trends for Printing Ultra Miniature Chips
Should We Measure Solder Paste Thickness?
Cleaning R.F. Circuits - Aqueous or Vapor?
Why Should We Consider Smart Feeders?
Ask the Experts
SMT Target Component Placement
Problems With Large Voids
Stainless Steel Benches and ESD
Exposed Copper Defect
What's Causing Cloudy Conformal Coating
Channels To Reduce Voids in Large Pads
Options for Reballing BGA Components
Aluminum Trays and Rapid Static Discharge