-
-
News
News Highlights
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueSilicon to Systems: From Soup to Nuts
This month, we asked our expert contributors to weigh in on silicon to systems—what it means to PCB designers and design engineers, EDA companies, and the rest of the PCB supply chain... from soup to nuts.
Cost Drivers
In this month’s issue of Design007 Magazine, our expert contributors explain the impact of cost drivers on PCB designs and the need to consider a design budget. They discuss the myriad design cycle cost adders—hidden and not so hidden—and ways to add value.
Mechatronics
Our expert contributors discuss the advent of mechatronics in PCB design, the challenges and opportunities this creates for circuit board designers, and the benefits—to the employee and the company—of becoming a mechatronics engineer.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - design007 Magazine
Book Excerpt: The Printed Circuit Assembler’s Guide to... Low-Temperature Soldering, Vol. 2, Chapter 3
August 7, 2024 | I-Connect007 Editorial TeamEstimated reading time: 1 minute
Mechanical Shock and Thermomechanical Reliability of Low-temperature Solder Hybrid Joints
HRL3 uses the individual and combined effects of solid solution strengthening, precipitate and dispersion hardening, grain refinement and diffusion modifiers to balance strength, toughness, stiffness, and ductility in their respective alloy compositions. Electronic systems under normal operating conditions are exposed to a diverse range of temperatures and mechanical loads, depending on operational environment and usage. Proxy tests such as mechanical drop shock and thermal cycling are often used to predict thermal and mechanical reliability performance of solder joints in actual devices.
Solder joints are cycled between cold and hot zones during thermal cycling tests and the materials forming the solder joint—the package, the solder, the interfacial intermetallic layer, and the substrate—will expand and contract at different rates. This is generally known as coefficient of thermal expansion (CTE) mismatch, in which these variations in CTE generate shear stresses at the interfaces between these materials and potentially lead to thermomechanical fatigue. Failures through fatigue can be divided into three stages: crack initiation, crack propagation, and sudden fast failure. There are competing mechanisms promoting crack growth and closure. While stronger materials resist crack initiation better, crack propagation depends on the plastic zone ahead of the crack tip, i.e., the alloy microstructure. Thus, the need to achieve a balanced alloy composition combining strength and microstructure optimization is required for improved fatigue life and optimal performance.
A solder paste formulated with HRL3 was evaluated for drop shock and thermal cycling performance using a Cu-OSP test vehicle and SAC305 CTBGA84 packages. Therefore, upon using the low-temperature solder paste to attach these packages to a PCB, a hybrid (or heterogeneous) LTS/SAC305 solder joint is formed. The solder paste was screen printed on a PCB by using two stencil apertures, 11 and 14 mil. Table 3.1 shows the corresponding paste volume to ball volume ratios (0.6 and 0.8) that enabled investigating the effect of paste volume on the mechanical and thermal reliability of their solder joints.
These PCBs were reflowed using the profiles shown in Figure 3.1. The HRL3 alloy was evaluated using two peak temperatures, 165°C and 175°C, while SAC305 was reflowed using its typical 245°C (all within +/-5°C) peak profile.
Suggested Items
Circuit Technology Center Announces Expanded Tinning Services Capacity
09/16/2024 | Circuit Technology CenterCircuit Technology Center announces it has expanded its electronic component tinning services capacity. Four (4) Hentec-Odyssey 1325 robotic hot solder dip machines are in full operation to meet the increasing demand from the defense and high-reliability customer base that requires component tinning services for tin whisker mitigation, gold mitigation, and lead re-conditioning.
The Knowledge Base: The Pivotal Role of Solder Paste
09/16/2024 | Mike Konrad -- Column: The Knowledge BaseIn the complex world of electronics manufacturing, the humble solder paste plays a pivotal role. Often overshadowed by more conspicuous electronics assembly equipment and materials, this blend of powdered metal and flux is the unsung hero that binds the electronic circuits together. But beyond its adhesive and conductive properties, the selection of the right solder paste is crucial for ensuring the long-term reliability of electronic devices.
I-Connect007 Editor’s Choice: Five Must-Reads for the Week
09/13/2024 | Marcy LaRont, PCB007 MagazineAt the top of my list is “Silicon to Systems,” an interview with technology experts from IPC: Matt Kelly, Devan Iyer, and Kris Moyer. Also, this week, we hear from I-Connect007 Managing Editor Nolan Johnson, who’s been in Mexico for SMTA Guadalajara. Speaking of Mexico, I want to highlight an interview that appeared in IPC Community between Lorena Villanueva and Barjouth Aguilar of Flex, who talk about the importance of sustainability. I wrap up my recommendations with articles about solder printing and wet process control.
Making Waves With Solder Paste Jetting
09/11/2024 | Josh Casper, Horizon SalesAs electronics shrink and PCB density grows, traditional solder deposition methods such as stencil printing face significant challenges. One solution making substantial waves is solder paste jetting. Solder paste jetting is no secret. In fact, the development and commercialization of this technology has been around since the early 2000s. So, why now? We’ve arrived at a time in which the maturity of this technology has intersected with new demands of electronics manufacturing.
Scrutinizing Solder Printing
09/10/2024 | Nolan Johnson, I-Connect007As members of the technical staff at Indium, Adam Murling, technical manager, and Ron Lasky, senior technologist and professor at Dartmouth University, know their way around metallurgy and solder formulation. I corralled them for a conversation on solder application techniques from the solder’s perspective and their insights did not disappoint.