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In this issue, we discuss some of the challenges, pitfalls and mitigations to consider when designing non-standard board geometries. We share strategies for designing odd-shaped PCBs, including manufacturing trade-offs and considerations required for different segments and perspectives.
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Book Excerpt: The Printed Circuit Designer’s Guide to... Thermal Management with Insulated Metal Substrates, Chapter 2October 10, 2023 | I-Connect007 Editorial Team
Estimated reading time: 1 minute
Chapter 2: Solder Cracks
Historically, engineering teams using some types of insulated metal substrates in high-performance LED applications have noted the formation of solder cracks after prolonged thermal cycles. Solder cracks, as the name suggests, are discontinuities in the solder joint, usually caused by excessive mechanical stress. This stress typically results from a mismatch between the coefficients of thermal expansion (CTE) of each of the joined components. Through repeated thermal cycling, the tendency of the joined parts to expand and contract at different rates eventually overcomes the solder’s ability to resist that differential displacement. A crack then forms in the solder. Crack formation like this can be aided by soldering defects such as poor wetting at either surface or inclusion of impurities within in the solder.
A solder crack impairs both the mechanical integrity of the joint and the electrical continuity. The mechanical weakness may not be detected, especially if there are several such connections and others are unaffected. The electrical discontinuity may be partial, manifested as increased ohmic resistance if the separated surfaces remain in contact, or may cause an intermittent open circuit. Each can cause defective functioning of the circuit or system.
Figure 2.1 shows possible root causes of such solder cracks. Although this list is not exhaustive, any combination of these effects can contribute towards conditions that cause solder cracks to occur.
As a designer and manufacturer of laminate, Ventec can directly influence multiple aspects relating to materials selection and use, including:
- Minimizing percentage of copper on circuit side
- Use Super HTE (High-Temperature Elongation) copper foil with lower tensile strength
- Lower Tg dielectric working in elastic deformation zone
- Lower CTE of aluminum baseplate (CTE is 19 ppm/K)
- Copper baseplate
- Choosing high-performing dielectric
In addition, the effect each crack or void in the solder joint has on the thermal path of the system must also be considered. A representative approximation is that a crack affecting 50% of the solder pad area will double the thermal impedance.
The SMTA Capital Chapter is excited to announce the upcoming SMTA Capital Chapter Expo and Tech Forum, scheduled for March 7th, 2024, at Sweeny Barn in Manassas, Virginia.
The opening session of the second day’s conference proceedings focused on global PCB trends and was introduced and moderated by Dr. Michele Stampanoni, vice president of strategic sales and business development at Cicor Group in Switzerland. He opened the session with Dr. Hayao Nakahara’s knowledgeable and enlightening video presentation on the IC substrates industry.
Saki’s Advanced Optical Inspection Boosts Quality Assurance at US-headquartered Smart Modular Technologies02/14/2024 | Saki Corporation
Saki Corporation, an innovator in the field of automated optical and X-ray inspection equipment, is pleased to announce that it has supplied inline optical inspection systems to Smart Modular Technologies, a Newark California based manufacturer of high-performance DRAM modules and solid-state disk drives (SSDs).
Ucamco is proud to release UcamX v2023.12 and Integr8tor v2023.12. These new versions of our CAM and Pre-CAM software include plenty of additions to increase our customers’ productivity, highlighted by the topics below.
Bittele Electronics, a leading provider of prototype and small-to-mid volume PCB assembly services, announces the expansion of its Markham assembly facility. The strategic move aims to improve inventory accuracy and streamline operations for valued customers.