Solder Bump Bonding via Compression Retraction Forces
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Solution Overview
Problem
The existing methods for forming electrical connections between solder bumps on a die and leads on a substrate often result in non-wet connections due to trapped non-conductive pastes, leading to weak and unreliable bonds that can fail prematurely.
Innovation Solution
A method involving a series of compression and retraction forces is applied to align and bond the solder bumps with the leads, disrupting the non-conductive coating to ensure a wet connection without traps, comprising a first compression to penetrate the coating, a retraction to break it, and subsequent compressions to establish a strong bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single compression force is applied to bond solder bumps to leads, then the bonding process is simple and fast, but traps of non-conductive paste remain and wet connections are not achieved
Solution Approach 1:
The patent applies periodic compression and retraction forces in multiple cycles during the bonding process. The compression phase forces solder bumps through non-conductive paste to contact leads, while the retraction phase allows molten solder to flow back and fill gaps, creating wet connections. This periodic action repeats multiple times to ensure complete removal of paste traps and formation of reliable electrical connections.
2Reliability
If compression force is applied to force solder bumps through non-conductive paste, then electrical connection is achieved, but the non-conductive paste creates traps that weaken the bond
Solution Approach 1:
The patent utilizes the phase transition of solder from solid to molten state during compression. When compression force is applied, solid solder bumps are forced through non-conductive paste to contact leads. Upon retraction, the molten solder flows back and solidifies, filling gaps and creating strong wet connections. The repeated phase transitions ensure complete displacement of paste and formation of robust bonds.
3Reliability
If multiple compression and retraction forces are applied to achieve wet connections, then connection reliability is improved, but the bonding process becomes more complex
Solution Approach 1:
The patent employs dynamic control of compression and retraction forces with varying magnitudes and durations across multiple cycles. Each cycle adapts the force parameters to achieve optimal solder flow and trap removal. The dynamic force application ensures reliable wet connections while the process remains integrated within the bonding apparatus, managing complexity through automated control.
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 consistently achieves a reliable, trap-free wet connection that enhances the electrical and mechanical strength of the bond between the die and the substrate, reducing the likelihood of premature failure.
Implementation Method 1
a heated condition. Solder bumps on the die are aligned with leads on the substrate and then forced together via a compressive force
Implementation Method 2
In the formation of a wet connection molten solder on the solder bump flows to or into the lead
Implementation Method 3
the substrate and die are compressed together under a heated condition
Implementation Method 4
forced together via a compressive force
Data Source
AI summary
Methods of connecting solder bumps located on dies to leads located on substrates are disclosed herein. One embodiment includes applying a first compression force between the solder bump and the lead; relieving the first compression force between the solder bump and the lead; and applying a second compression force between the solder bump and the lead.