Stepped Conductive Pad for Semiconductor Package Reliability
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Solution Overview
Problem
Semiconductor package devices face challenges with lateral stress delamination and uneven intermetallic compound (IMC) formation due to non-uniform barrier layers on solder pads, which affects connection reliability and hinders miniaturization and increases manufacturing costs.
Innovation Solution
A semiconductor package device with a conductive pad structure comprising multiple metal layers, where a first metal layer is partially disposed within a cavity of a dielectric layer and a second metal layer extends along the lateral surface, providing a stepped structure that enhances bonding strength and prevents direct contact between the electrical contact and inner layers, thereby reducing IMC formation and delamination risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a non-solder mask defined (NSMD) type solder pad is used to expose the lateral surface of the solder pad for connection, then the connection can sustain lateral stress better, but an uneven intermetallic compound (IMC) layer is formed which tends to crack and causes soldering issues
Solution Approach 1:
The conductive pad is divided into multiple metal layers (first metal layer and second metal layer) with different functions. The first metal layer provides lateral stress resistance by extending along the lateral surface, while the second metal layer provides a uniform bonding surface for the electrical contact, preventing uneven IMC formation. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
The second metal layer acts as an intermediary between the electrical contact and the first metal layer. It prevents direct contact between the electrical contact and the non-uniform barrier layer on the lateral surface, thereby avoiding uneven IMC formation and cracking. The intermediary layer ensures uniform IMC formation while maintaining the lateral stress resistance provided by the first metal layer.
2Reliability
If the thickness of the conductive pad is increased to avoid IMC issues, then connection reliability is improved, but the total size of the semiconductor package device increases which hinders miniaturization
Solution Approach 1:
Instead of increasing the thickness (vertical dimension) of the conductive pad to ensure reliable connection, the invention extends the first metal layer along the lateral surface (lateral dimension). This dimensional shift allows the conductive pad to maintain thin profile for miniaturization while achieving reliable connection through lateral extension that sustains lateral stress without requiring excessive thickness.
3Volume of moving object
If a chip-last fan-out process is used to enable miniaturization with thinner conductive pads, then device size is reduced, but IMC issues affect electrical performance
Solution Approach 1:
The conductive pad structure is segmented into multiple metal layers where the second metal layer specifically addresses the IMC issue by providing a uniform bonding surface, enabling thin conductive pads to achieve reliable electrical performance in chip-last fan-out processes.
Solution Approach 2:
The second metal layer serves as an intermediary that prevents direct interaction between the electrical contact and the non-uniform barrier layer, ensuring uniform IMC formation even with thin conductive pads, thus enabling miniaturization without compromising electrical performance.
Data Source
AI summary
A semiconductor package device includes an interconnection structure, an electronic component, a package body and an electrical contact. The dielectric layer has a top surface and a bottom surface. The dielectric layer defines a cavity extending from the bottom surface into the dielectric layer. A patterned conductive layer is disposed on the top surface of the dielectric layer. The conductive pad is at least partially disposed within the cavity and electrically connected to the patterned conductive layer. The conductive pad includes a first metal layer and a second metal layer. The second metal layer is disposed on the first metal layer and extends along a lateral surface of the first metal layer. The electronic component is electrically connected to the patterned conductive layer. The package body covers the electronic component and the patterned conductive layer. The electrical contact is electrically connected to the conductive pad.