Land on Via Structure for Solder Ball Height Control
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Solution Overview
Problem
The NSMD structure in semiconductor devices experiences variations in solder ball height due to misalignment between land and opening, leading to potential mounting failures, while the SMD structure has weak adhesion between lands and solder balls, resulting in reduced coupling life.
Innovation Solution
A semiconductor device with a land on via structure where lands are directly formed on vias without wiring, and openings are larger than lands to contain them, ensuring uniform exposure and improved adhesion, while omitting unnecessary wiring to reduce stress and impedance in high-frequency circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NSMD structure is used with misalignment between land and opening, then manufacturing is easier, but solder ball height varies leading to mounting failures
Solution Approach 1:
The patent applies preliminary action by pre-forming the land pattern with precise dimensions and positioning before applying solder paste. The land width and length are specifically designed to accommodate the solder ball footprint, ensuring that even with minor alignment variations during assembly, the solder ball remains properly positioned on the land, thereby preventing mounting failures while maintaining ease of manufacture.
Solution Approach 2:
The patent employs parameter changes by optimizing the land dimensions (width and length) and the opening dimensions in the solder resist layer. By carefully controlling these parameters, the land area is ensured to be sufficiently large to accommodate solder ball height variations, while the opening is sized to allow proper solder paste application. This parameter optimization resolves the contradiction between manufacturing ease and mounting reliability.
2Measurement precision
If SMD structure is used with opening smaller than land, then solder ball positioning is improved, but adhesion between land and solder ball becomes weak reducing coupling life
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the land dimensions and opening dimensions. The land width and length are set to provide sufficient adhesion area for the solder ball, while the opening in the solder resist is sized to allow proper solder paste application and positioning. Specifically, the land area is designed to be larger than the opening area, ensuring both precise positioning and strong adhesion, thereby extending coupling life while maintaining positioning precision.
Solution Approach 2:
The patent applies preliminary action by pre-forming the land pattern with optimized dimensions before solder paste application. The land is prepared in advance with sufficient area to ensure strong adhesion, and the opening is pre-defined in the solder resist to guide solder paste placement. This preliminary preparation ensures both precise solder ball positioning and strong adhesion, resolving the contradiction between positioning precision and coupling life.
3Reliability
If wiring is added to connect land and via, then electrical coupling is achieved, but stress and impedance increase in high-frequency circuits
Solution Approach 1:
The patent applies merging by integrating the land directly onto the via structure, eliminating the need for separate wiring connections. The land is formed as a continuous conductive structure that sits directly on the via, creating a seamless electrical pathway. This merging of land and via reduces the number of discrete components and connections, thereby minimizing stress concentration points and reducing impedance in high-frequency circuits while maintaining reliable electrical coupling.
Solution Approach 2:
The patent extracts the unnecessary wiring element from the electrical connection path between land and via. By removing the intermediate wiring and directly coupling the land to the via, the patent eliminates the additional stress and impedance that would be introduced by the wiring. This extraction of the redundant wiring component achieves reliable electrical coupling with minimal harmful factors in high-frequency applications.
Data Source
AI summary
The present invention provides a technique capable of suppressing variations in the height of each solder ball where an NSMD is used as a structure for each land. Vias that extend through a wiring board are provided. Lands are formed at the back surface of the wiring board so as to be coupled directly to the vias respectively. The lands are respectively formed so as to be internally included in openings defined in a solder resist. Half balls are mounted over the lands respectively. Namely, the present invention has a feature in that the configuration of coupling between each of the lands and its corresponding via both formed at the back surface of the wiring board is taken as a land on via structure and a configuration form of each land is taken as an NSMD.