Composite Bump Structure for Reliable Interconnects
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Solution Overview
Problem
Existing connecting structures using anisotropic conductive films face issues with conductive particles in intermediate regions causing insulation disturbances and short circuits, especially with increasing demand for smaller electronic components and varying substrate irregularities.
Innovation Solution
A connecting structure utilizing a bump formed from a combination of anisotropic conductive pastes with different conductive properties, where the first member is formed from a thermoset resin-based paste and the second member is either a conductive material or another anisotropic conductive paste with varying density, ensuring reliable electrical connection and stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anisotropic conductive film is used for connecting terminals, then stress is relaxed and cracks are prevented, but conductive particles in intermediate regions cause insulation disturbances and short circuits
Solution Approach 1:
The connecting structure is divided into multiple segments: a first anisotropic conductive paste for stress relaxation and a second conductive material for reliable electrical connection. This segmentation allows each material to perform its specific function without interfering with the other, preventing short circuits while maintaining connection reliability.
Solution Approach 2:
Different regions of the bump are assigned different material properties: the first anisotropic conductive paste provides stress relaxation properties, while the second conductive material provides high electrical conductivity. This local differentiation ensures that each region contributes its specific quality to solve the contradiction between stress relaxation and electrical connection.
2Reliability
If solder balls are used for connecting terminals, then strong electrical connection is achieved, but stress concentration causes distortion and cracks in hard substrates
Solution Approach 1:
The bump is constructed as a composite material structure combining an anisotropic conductive paste and a conductive material. The anisotropic conductive paste component provides stress relaxation properties similar to soft materials, while the conductive material ensures strong electrical connection, thus resolving the contradiction between connection strength and stress resistance.
3Volume of moving object
If terminal distance is reduced to decrease device size, then miniaturization is achieved, but insulation between adjacent terminals becomes difficult to maintain
Solution Approach 1:
The harmful conductive particles in intermediate regions are extracted and removed from the system. By using a second conductive material that is precisely positioned and controlled, only the necessary conductive path between terminals is created, eliminating stray particles that could cause short circuits in miniaturized devices.
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 solution ensures reliable electrical connections between substrates and electronic devices, even with large surface irregularities and varying distances between terminals, while preventing short circuits and maintaining insulation characteristics.
Implementation Method 1
the thermoset resin included in the anisotropic conductive paste can relax a stress applied to an interface between the bump and the connecting terminal
Implementation Method 2
when being compressed by applying a constant load, the particles of the conductive material contact each other to thereby have a conductivity in a compressive direction
Data Source
AI summary
A connecting terminal provided on a substrate and a connector provided on an electronic device are connected via a bump formed of a first member, which is formed of an anisotropic conductive paste including particles of a conductive material, and a second member which is different in conductivity from the first member. According to such a structure, since the anisotropic conductive paste which is softer as compared to a solder bump is used, stress applied to an interface between the bump and the connecting terminal is relaxed. Accordingly, reliability of connection can be assured even when using a substrate with large surface irregularities and/or bending, in which stress occurs relatively easily in a connection part of the bump and the connecting terminal.