Copper Core Ball Interconnect Geometry for Reliable Substrate Bonding
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Solution Overview
Problem
Existing semiconductor packages face challenges in achieving high connection reliability between copper core balls and substrates, which are used to connect upper and lower substrates.
Innovation Solution
The semiconductor apparatus employs copper core balls with a maximum dimension in the vertical direction that is smaller than their maximum diameter in the horizontal plane, allowing for surface-to-surface contact with conductive pads, and a solder layer that spreads over the pads during reflow, ensuring a wide contact area and secure bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spherical conductive core ball is used to connect upper and lower substrates, then the connection structure is simple and manufacturing is easy, but the contact area with conductive pads is small resulting in lower connection reliability
Solution Approach 1:
The conductive core ball is designed with an asymmetric shape where the maximum dimension in the vertical direction is smaller than the maximum diameter in the horizontal plane. This asymmetric geometry enables the core ball to form extended contact surfaces with the conductive pads on both upper and lower substrates, significantly increasing the contact area and connection reliability while maintaining manufacturing simplicity
Solution Approach 2:
The invention transitions from a traditional spherical core ball (equal dimensions in all directions) to an ellipsoidal shape with different dimensions in vertical versus horizontal directions. This dimensional change allows the core ball to provide both wide horizontal contact area for pad connection and controlled vertical height for substrate spacing, resolving the contradiction between contact area and structural simplicity
2Length of stationary object
If the solder layer volume is reduced during reflow, then the height of the semiconductor package is shortened, but the bonding strength between substrates may be compromised
Solution Approach 1:
The conductive core ball serves as a composite structural element that combines mechanical support function (maintaining substrate spacing) with electrical connection function (providing conductive path). The core ball's metallic material compensates for the reduced solder volume, ensuring bonding strength is maintained even when solder layer volume is minimized for shorter package height
Solution Approach 2:
The invention changes the geometric parameters of the conductive core ball (making vertical dimension smaller than horizontal diameter) to optimize the distribution of contact pressure and stress. This parameter change allows the system to achieve adequate bonding strength with reduced solder volume, as the core ball's geometry distributes mechanical loads more effectively across the contact surfaces
Data Source
AI summary
A semiconductor apparatus includes a first substrate having a first surface and a first conductive pad on the first surface, a second substrate having a second surface opposing the first surface, and having a second conductive pad on the second surface, a semiconductor device disposed between the first substrate and the second substrate and mounted on the first surface of the first substrate, and a conductive core ball in contact with the first conductive pad and the second conductive pad, wherein a maximum dimension of the conductive core ball in a first direction perpendicular to the first surface is smaller than a maximum diameter of the conductive core ball in a plane parallel to the first surface, and wherein the conductive core ball includes a first contact surface in direct contact with the first conductive pad, and a second contact surface in direct contact with the second conductive pad.