Gold Electrode Connection Structure for Low-Temperature Reliable Bonding
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Solution Overview
Problem
The challenge in semiconductor packaging is to maintain conduction reliability and insulation reliability, especially with the decrease in connection temperature and size, where traditional soldering methods face issues with stress from thermal expansion and brittleness, leading to breakage and limitations in using low-temperature solders.
Innovation Solution
A connection structure using a gold electrode with a bonding portion comprising a tin-gold alloy and bismuth regions, where 90% or more of the bonding portions include a tin-gold alloy for high melting point and a bismuth region for reinforcement, and an anisotropically conductive film with solder particles of specific size and distribution for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lead-free solder with silver or copper added to tin is used for reflow at 260°C, then soldering strength is improved, but thermal expansion stress causes breakage and alloy layer formation promotes breakage
Solution Approach 1:
The patent changes the solder composition parameters by adding bismuth to create a tin-bismuth-based solder with specific composition ratios (Bi: 3-15 wt%, Sn: 85-96 wt%, Cu: 0.1-5 wt%). This parameter change allows the solder to maintain strength while reducing thermal expansion stress and preventing excessive alloy layer formation, thereby improving connection reliability.
Solution Approach 2:
The patent creates a composite solder material combining tin, bismuth, and copper elements. This composite material leverages the low melting point of tin, the brittleness control of bismuth, and the strength enhancement of copper to achieve both adequate soldering strength and reduced thermal stress, resolving the contradiction between strength and reliability.
2Temperature
If tin-bismuth solder with melting point of 200°C or lower is used, then reflow temperature is reduced, but bonding portion becomes brittle and easily broken by impact
Solution Approach 1:
The patent optimizes the bismuth content parameter within a specific range (3-15 wt%) to balance melting point and impact resistance. This parameter optimization ensures the solder melts at low temperature (below 200°C) while maintaining adequate impact resistance through controlled brittleness, preventing the bonding portion from being too brittle.
Solution Approach 2:
The patent introduces copper (0.1-5 wt%) as a local quality enhancer that specifically improves impact resistance without significantly affecting the low-temperature melting characteristic. This localized property enhancement allows the solder to have both low melting point and improved toughness against impact.
3Volume of moving object
If connection temperature and size are decreased for high definition circuit members, then miniaturization is achieved, but conduction reliability becomes difficult to secure
Solution Approach 1:
The patent changes the material composition parameters of the solder to create a eutectic or near-eutectic alloy with optimized mechanical and electrical properties. This parameter change enables reliable conduction in miniaturized connections by ensuring proper wetting, adhesion, and electrical conductivity even at reduced connection sizes.
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 provides a connection structure with improved conduction and insulation reliability, suppressing cracking and melting, and is suitable for high-temperature environments, enabling reliable connections in compact semiconductor packages.
Implementation Method 1
a solder particle containing a tin-bismuth alloy, the melting point of which is 200° C. or lower
Implementation Method 2
anisotropically conductive materials such as an anisotropically conductive film and an anisotropically conductive paste have been hitherto used
Data Source
AI summary
A connection structure including: a first circuit member having a plurality of first electrodes; a second circuit member having a plurality of second electrodes; and an intermediate layer having a plurality of bonding portions electrically connecting the first electrodes and the second electrodes, in which at least one of the first electrode and the second electrode that are connected by the bonding portion is a gold electrode, and 90% or more of the plurality of bonding portions include a first region containing a tin-gold alloy and connecting the first electrode and the second electrode and a second region containing bismuth and being in contact with the first region.