Wiring Substrate Connection Pad Crack Resistance
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Solution Overview
Problem
Coreless wiring substrates face reliability issues due to cracks generated from the periphery of connection pads progressing to the inner layer side during drop tests, leading to reduced production yield and module reliability.
Innovation Solution
A wiring substrate design featuring a connection pad structure with a first metal layer, an intermediate metal layer with higher hardness, and a second metal layer, where the intermediate metal layer is positioned between the first and second metal layers and protrudes from their outer edges, preventing crack progression through its higher hardness and protrusion portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a coreless wiring substrate is used, then the substrate weight and complexity are reduced, but cracks are easily generated from the periphery of the connection pad to the inner layer side during drop tests
Solution Approach 1:
The connection pad is constructed as a composite structure with three metal layers having different hardness values. The intermediate metal layer has higher hardness than both the first and second metal layers, creating a hardness gradient that prevents crack propagation while maintaining overall structural integrity. This composite approach allows the soft outer layers to absorb impact energy while the hard intermediate layer acts as a barrier to crack progression.
Solution Approach 2:
The invention applies different hardness properties to different regions of the connection pad structure. The intermediate metal layer with higher hardness is positioned specifically at the interface region where cracks typically initiate and propagate, while the first and second metal layers maintain lower hardness for flexibility and bonding. This localized quality differentiation addresses the specific stress concentration zone without compromising the entire pad structure.
2Ease of manufacture
If the connection pad is made with uniform metal composition, then the manufacturing process is simplified, but crack resistance during drop tests is insufficient
Solution Approach 1:
The connection pad employs a three-layer composite metal structure with distinct hardness characteristics. The intermediate layer uses a harder metal material to create a mechanical barrier against crack propagation, while the outer layers use softer metals for bonding and flexibility. This composite construction enhances reliability without significantly complicating the manufacturing process, as the layers can be deposited sequentially using standard electroplating or sputtering techniques.
Solution Approach 2:
The connection pad is segmented into three distinct metal layers, each with specific functional characteristics. The first metal layer provides bonding to the insulating layer, the intermediate metal layer provides crack resistance through higher hardness, and the second metal layer provides bonding to the solder bump. This segmentation allows each layer to be optimized for its specific function while maintaining manufacturability through sequential deposition processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively stops crack progression from the connection pad periphery to the inner layer side, enhancing the production yield and reliability of electronic component modules by providing a higher hardness barrier.
Implementation Method 1
a hardness of the intermediate metal layer is higher than a hardness of the first metal layer and the second metal layer
Implementation Method 2
forming a metal laminated portion including a first metal layer, an intermediate metal layer, and a second metal layer in sequence from a bottom, in the opening portion of the resist by an electroplating
Data Source
AI summary
A wiring substrate includes an insulating layer, a wiring layer buried in the insulating layer, and a connection pad connected to the wiring layer via a via conductor provided in the insulating layer and in which at least a part is buried in an outer surface side of the insulating layer, wherein the connection pad includes a first metal layer (a first copper layer) arranged on the outer surface side, an intermediate metal layer (a nickel layer) arranged on a surface of an inner layer side of the first metal layer, and a second metal layer (a second copper layer) arranged on a surface of an inner layer side of the intermediate metal layer, and a hardness of the intermediate metal layer is higher than a hardness of the first metal layer and the second metal layer.