PCB Conductive Pad Arc-Opening Design for Thermal Stress Distribution
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Solution Overview
Problem
In electronic devices with half-board shaped Printed Circuit Boards (PCBs), the Power Management Semiconductor Chip (PMIC) located on the rear face cannot be easily relocated when thermal shocks occur, leading to potential cracks in the semiconductor chip due to unbalanced conductive pad shapes.
Innovation Solution
A PCB design featuring a bonding structure with arc-shaped openings and overlapping regions on the conductive pads, which helps distribute thermal stress and prevent cracks in semiconductor chips during thermal shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the PMIC is located on the rear face of the PCB in a half-board shape configuration, then mounting density is increased, but the bonding structure becomes vulnerable to thermal shock causing cracks in the semiconductor chip
Solution Approach 1:
The conductive pad is divided into multiple regions: a first region with a first shape and a second region with a second shape extending from the first region. This segmentation allows different parts of the pad to serve different functions - the first region provides the primary bonding area while the second region extends to balance the pad shape and distribute thermal stress, preventing cracks in the bonding structure during thermal shock
Solution Approach 2:
The conductive pad employs an asymmetric design where the second region extends in a specific outer circumferential direction from the first region. This asymmetric extension balances the overall pad shape relative to the semiconductor chip bonding area, creating a more uniform stress distribution pattern that prevents crack propagation during thermal cycling while maintaining high mounting density
2Ease of manufacture
If the conductive pad has an unbalanced shape, then manufacturing is simplified, but cracks occur in the semiconductor chip due to unbalanced thermal stress distribution
Solution Approach 1:
The conductive pad features localized quality variations with different regions having distinct geometries. The first region provides a compact bonding area while the second region extends in a specific direction to locally balance the pad shape. This local quality adjustment ensures uniform thermal stress distribution at critical bonding areas without complicating the overall manufacturing process
Solution Approach 2:
The conductive pad geometry is pre-designed with the second region extending from the first region to anticipate and prevent thermal stress concentration before thermal shock occurs. This preliminary geometric configuration ensures that when thermal cycling happens, the stress is already distributed uniformly across the bonding interface, preventing crack initiation in the semiconductor chip
Data Source
AI summary
An electronic device according to an embodiment may include: a Printed Circuit Board (PCB) including a first face and a second face; a semiconductor chip mounted on the second face; a conductive pad disposed on the second face; a solder resist layer disposed on the second face and including an aperture; an arc-shaped opening having an inner diameter and an outer diameter, disposed along an outer periphery of the conductive pad and in the aperture; and at least one external terminal disposed on the semiconductor chip and bonded to the conductive pad. The conductive pad may include: a first region having a smaller diameter than the outer diameter; and at least one second region extending from the first region in a first outer circumferential direction, and located at least in part between both ends of the opening. In addition, various embodiments recognized through the specification may also be possible.