Cone-Shaped Metal Bumps for Stepped Substrate Connections
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Solution Overview
Problem
Existing methods for connecting pads and bumps face challenges in achieving reliable electrical connections when there are height differences, leading to low reliability in connections between package substrates and device chips.
Innovation Solution
The method involves forming cone-shaped metal bumps of different heights to correct step height differences between connection surfaces, ensuring uniform joining conditions and preventing short-circuits by compressing the bumps to accommodate variations in height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional joining methods are used on stepped connection surfaces, then the manufacturing process is simple, but the electrical connection reliability is low due to height differences
Solution Approach 1:
The patent applies local quality by forming metal bumps with different heights corresponding to different regions (first region and second region) of the connection surface. Each bump's height is specifically tailored to compensate for the step height in its respective region, ensuring that all bump tips reach the same level after compression, thereby achieving reliable electrical connections across the stepped surface.
Solution Approach 2:
The patent employs preliminary action by pre-forming metal bumps with different heights before the joining process. This preliminary height differentiation compensates for the step differences in advance, so that when compression is applied, all bumps make contact with the opposing electrode simultaneously, ensuring uniform joining conditions and high connection reliability.
2Ease of manufacture
If uniform bump heights are used, then the manufacturing process is simple, but short-circuits occur due to height variations in the connection surface
Solution Approach 1:
The patent implements local quality by creating metal bumps with non-uniform heights that correspond to the local topography of the connection surface. Bumps in the first region have one height while bumps in the second region have a different height, allowing each to compensate for the step difference in its region and prevent short-circuits while maintaining manufacturing feasibility.
3Reliability
If different joining forces are applied to different regions, then connection reliability is improved, but the joining process complexity increases
Solution Approach 1:
The patent applies equipotentiality by designing the metal bump heights such that after compression, all bump tips reach the same final level regardless of their initial height differences. This eliminates the need for complex region-specific force control, as a uniform compression force achieves uniform joining results across the entire stepped surface.
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 enhances the reliability of electrical connections by ensuring consistent joining forces and characteristics across the connection surfaces, improving the overall reliability of the electronic circuit.
Implementation Method 1
a metal microparticle ejecting means that ejects metal microparticles together with a carrier gas through a nozzle to the held substrate, the ejected metal microparticles being deposited at a predetermined location of a metal wiring to form a cone-shaped metal bump by a gas deposition method
Implementation Method 2
the substrate holding means has a cooling member which is formed in a size and shape larger than the lower surface of the substrate and which is composed of a metal heat radiation plate that holds the substrate from the other surface side, a flexible thermally conductive sheet interposed between the substrate and the cooling member
Implementation Method 3
the first metal bump and the second metal bump have different heights so as to correct a height of the step
Data Source
AI summary
The purpose of the present invention is to provide an electronic circuit connection method and an electronic circuit capable of improving the reliability of electrical connection.A connection method for an electronic circuit 100 includes: a process of forming a first metal bumps 30 and a second metal bump 40, each of which has a cone shape; and a process of joining a first electrode pad 12 and a third electrode pad 22 by the first metal bump 30 and joining a second electrode pad 13 and a fourth electrode pad 23 by the second metal bump 40, wherein at least one region of between a first region 11a and a second region 11b in a first connection surface 11 and between a third region 21a and a fourth region 21b in a second connection surface 21 has a step 11c, and the first metal bump 30 and the second metal bump 40 have different heights so as to correct a height H1 of the step 11c.