Electroplated Conductive Posts for Fine-Pitch Semiconductor Substrates
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Solution Overview
Problem
Current flip-chip technology faces challenges in forming fine-pitch electroplated conductive posts due to alignment issues and stress caused by temperature variations, leading to increased intervals between posts and potential overfill during packaging.
Innovation Solution
A semiconductor package substrate structure with electroplated conductive posts that fully cover the connecting pads, where an insulating protective layer is formed after electroplating, exposing the posts through recesses or openings to reduce stress and allow for more precise alignment, and underfill confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the aperture of openings is reduced to enable fine-pitch conductive posts, then manufacturing precision is improved, but alignment precision deteriorates due to machine limitations
Solution Approach 1:
The insulating protective layer is formed with openings before the electroplating process. This preliminary preparation ensures that the conductive posts are deposited in precisely defined locations, eliminating alignment issues that would occur if openings were created after electroplating. The pre-formed openings serve as templates that guide the electroplating process, ensuring accurate positioning even for fine-pitch applications.
Solution Approach 2:
The conventional sequence is inverted: instead of forming openings in the insulating layer after electroplating to create conductive posts, the patent forms the openings in the insulating protective layer before electroplating. This reversal allows the electroplating process to deposit conductive material directly into pre-defined openings, ensuring precise positioning and eliminating the need for subsequent alignment operations.
2Measurement precision
If the aperture of openings is enlarged to improve alignment, then alignment precision is improved, but the interval between conductive posts increases, hindering fine-pitch bump formation
Solution Approach 1:
The insulating protective layer with precisely sized openings is formed before electroplating. This preliminary structure defines the exact positions and sizes of conductive post locations, allowing for fine-pitch spacing without requiring enlarged openings for alignment. The pre-formed openings ensure that conductive posts are deposited only in the intended locations with precise spacing.
Solution Approach 2:
The insulating protective layer provides localized definition of conductive post positions through precisely patterned openings. Each opening is individually sized and positioned to accommodate fine-pitch requirements, while the overall structure maintains appropriate spacing. This local quality control allows fine-pitch conductive posts to be formed without requiring global enlargement of all openings.
3Ease of manufacture
If electroplated conductive posts form projected wings on the insulating layer, then ease of manufacture is improved, but stress concentration occurs due to temperature variation and CTE difference
Solution Approach 1:
The harmful projected wings are eliminated by removing excess conductive material after electroplating. The conductive posts are trimmed or etched back to be flush with or recessed below the insulating protective layer surface, removing the source of stress concentration while maintaining the electrical connection function. This extraction of the harmful feature preserves the beneficial electrical conductivity.
Solution Approach 2:
The insulating protective layer is designed with openings that prevent the formation of projected wings during electroplating. By controlling the opening dimensions and positioning, the electroplating process deposits conductive material that remains contained within the opening boundaries, preventing protrusion and subsequent stress concentration. This preliminary design prevents the harmful effect before it occurs.
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
This approach enables the formation of fine-pitch electroplated conductive posts with reduced stress and improved bonding strength, while minimizing the overall package thickness and preventing overfill, enhancing the precision and reliability of the semiconductor package.
Implementation Method 1
an electroplating process is performed on the circuit board 11. Owing to the conductive property of the conductive layer 13 which acts as an electrical conduction path during electroplating, electroplated conductive posts 15 can be formed
Implementation Method 2
Owing to the conductive property of the conductive layer 13 which acts as an electrical conduction path during electroplating
Data Source
AI summary
A semiconductor package substrate structure and a manufacturing method thereof are disclosed. The structure includes a substrate having a plurality of electrical connecting pads formed on at least one surface thereof; a plurality of electroplated conductive posts each covering a corresponding one of the electrical connecting pads and an insulating protective layer formed on the surface of the substrate and having a revealing portion for exposing the electroplated conductive posts therefrom. The invention allows the interval between the electroplated conductive posts to be minimized, the generation of concentrated stresses and the overflow of underfill to be avoided, as well as the reduction of the overall height of the fabricated package.