Combing Automated Advanced Process Control with Feedback to Revolutionize the Printed Circuit Board Assembly Process
Reliability of No-clean and Water-soluble Solder Pastes
Design and Fabrication of Ultra-Thin Flexible Substrate
Vapor Phase - Improvement Under Oxidation Free Soldering Conditions
The Perfect Copper Surface
Atmospheric Plasma Surface Engineering of Printed Circuit Boards
Stencil Aperture Design for Next Generation Ultra Fine Pitch Printing
Hybrid Conformal Coatings Used for Mitigating Whisker Growth
Latest Industry News
The Other Risk of Using Toxic Materials
Germany Leads the Autonomous Vehicle Regulation Race
China is kicking out more than half the world’s bitcoin miners – and a whole lot of them could be headed to Texas
The Development of Hybrid Therma-EMI Solutions for Electronics
Detect PCB Stack-up Error with Machine Learning Methods
Rocket men: Bezos, Musk and Branson scramble for space supremacy
Billionaire Alibaba founder Jack Ma spending his time on philanthropy and hobbies like painting
World Wide Web code that changed the world up for auction as NFT

Effects of Mixing Solder Sphere Alloys with Bismuth-Based Pastes

Effects of Mixing Solder Sphere Alloys with Bismuth-Based Pastes
In this paper, the effect of mixing solder sphere alloys with Bi-based solder pastes on the component reliability in accelerated thermal cycling is studied.
Materials Tech


Authored By:

Francy John Akkara, Cong Zhao, Mohammed Abueed, Sinan Su, Sa’d Hamasha, Jeffrey Suhling, Pradeep Lall, Ph.D.
Department of Industrial and Systems Engineering
Auburn University


Reliability of the new solder alloys has been a serious concern, especially in the harsh environment. Aging at elevated temperature alters the structural and mechanical properties of the solder joint and leads to the coarsening of the precipitates in the bulk solder and growth of the intermetallic compound layer, which in turn deteriorates the solder joint. Various new elements such as bismuth, antimony, and nickel are micro-alloyed into the SnAgCu based alloys to slow down this deterioration process and improve the reliability. There haven’t been many studies about the effect of solder sphere alloys with bismuth pastes on the harsh thermal reliability. In this paper, the effect of mixing solder sphere alloys (SAC105, SAC305, matched solder sphere - paste) with Bi-based solder pastes on the component reliability in accelerated thermal cycling is studied.

Two surface finishes, namely OSP (Organic Solderability Preserve) and ImAg (Immersion Silver) are considered. The test vehicle consists of 15mm and 6mm Ball Grid Array (BGA) components. The assembled test boards were isothermally aged at 125oC for 12 months, which are then thermally cycled between -40oC to +125oC for 5800 cycles. Two-parameter Weibull analysis is done for all combinations. ANOVA is done to observe the main effects and interaction effects. Representative cross sections are also presented with IMC (intermetallic compound) layer thickness measurement.


The effect of using different solder spheres with different solder pastes and surface finishes were studied in the paper. In most of the cases, the failures were due to recrystallization and precipitate formation. It was observed that solder spheres, indeed had a significant effect on the reliability than the surface finish. This fact was clear from the ANOVA analysis and from the observation that the cracks, which led to failure were on the component side and not much cracks were found on the board side. EDX analysis needs to be done in order to understand more about the precipitates.

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
Component Moisture Question?
5 vs 8-Zone Ovens
How To Verify Cleanliness After Rework and Prior to Re-coating?
BGA Components and Coplanarity
Demise of the Plated-Through Hole?
What is Solder Paste Working Life on a Stencil?
Simple Test for Flux Penetration
Step Stencil Setup
Ask the Experts
Double sided SMT
Is lead contamination during cleaning of PB-free stencils possible?
BGA re-balling process
Using Solder Paste Beyond the Expiration Date
Conformal Coating Recommendation
Matte Black Solder Mask Defects
Oxidation of Solder Balls During Secondary Reflow
Rise of Bismuth Levels in our Solder Pots