Substrate Conductive Bumps Coplanarity via Height Compensation
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Solution Overview
Problem
The challenge is to maintain coplanarity between conductive bumps of varying diameters on a substrate, as the reflow process often results in inconsistent heights, exceeding the 8 μm difference requirement, leading to potential short circuits and reliability issues in electronic bonding.
Innovation Solution
The substrate structure incorporates first and second conductive bumps with specific material and layer configurations, where the second bumps have a greater height and narrower width, with metal layers and pre-solder layers of varying melting points, allowing for uniform height post-reflow and meeting coplanarity requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conductive bumps of uniform width and height are used on conductive pads of different diameters, then the manufacturing process is simple, but the coplanarity requirement cannot be met after reflow process
Solution Approach 1:
The patent applies local quality by configuring different bump structures for different pad types: first conductive bumps with first height for first conductive pads, and second conductive bumps with second height for second conductive pads. This localized differentiation ensures that after reflow process, all conductive bumps achieve coplanarity despite starting with different configurations, thereby solving the contradiction between manufacturing simplicity and coplanarity precision.
2Adaptability or versatility
If conductive pads have different diameters to meet I/O count and probe test requirements, then functional requirements are satisfied, but height difference between conductive bumps exceeds 8 μm after reflow
Solution Approach 1:
The patent implements local quality by assigning different height specifications to conductive bumps based on their underlying pad diameter. First conductive bumps on larger pads have first height, while second conductive bumps on smaller pads have second height. This localized adaptation allows the substrate to accommodate both I/O count requirements (smaller pads) and probe test requirements (larger pads) while ensuring all bumps achieve coplanarity after reflow, thus maintaining reliability.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the conductive bumps with different heights before the reflow process. The first conductive bumps are formed with first height and second conductive bumps with second height on the substrate before bonding. This preliminary differentiation compensates for the varying pad diameters, ensuring that after reflow, all bumps will be coplanar within 8 μm height difference, thereby preventing short circuits and ensuring bonding reliability.
3Ease of manufacture
If same thickness pre-solder layers are used on conductive bumps of different widths, then material usage is uniform, but height inconsistency occurs after reflow process
Solution Approach 1:
The patent applies local quality by specifying different height requirements for pre-solder layers on different bump types. The first pre-solder layer on first conductive bumps is configured to achieve first height after reflow, while the second pre-solder layer on second conductive bumps is configured to achieve second height. This localized differentiation in pre-solder layer configuration ensures that despite uniform material application processes, the final bump heights are precisely controlled to achieve coplanarity.
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 configuration ensures that the height difference between conductive bumps is compensated, achieving uniform heights and enhanced bonding reliability, thereby meeting the coplanarity requirement and preventing short circuits.
Implementation Method 1
the first and second pre-solder layers 111, 121 are reflowed into solder balls 111′, 121′
Data Source
AI summary
A substrate structure is provided, which includes a substrate body having a plurality of conductive pads, and a plurality of first conductive bumps and a plurality of second conductive bumps disposed on the conductive pads. Each of the second conductive bumps is less in width than each of the first conductive bumps, and is of a height with respect to the substrate body greater than a height of each of the first conductive bumps with respect to the substrate body. Therefore, the height difference between the first pre-solder layer and the second pre-solder layer after a reflow process can be compensated, and the first conductive bumps and the second conductive bumps thus have a uniform height.