Transparent Thin Substrate Laser Bonding for Small Flip-Chip Pads
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Solution Overview
Problem
The second flip-chip bonding method, which uses anisotropic conductive adhesive, often results in incomplete contact between chip electrodes and conductive balls, leading to decreased production yield, and attempts to increase electrode area to prevent this limit further chip area reduction.
Innovation Solution
An electronic device with a substrate having transmittance characteristics and a trace layer with connection pads, where electronic components are eutectically bonded using laser bonding, allowing for improved connection yield and reduced electrode and pad areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of chip electrode is increased to ensure complete contact with conductive balls, then the bonding yield is improved, but the chip area cannot be further reduced
Solution Approach 1:
The patent replaces the mechanical pressing method with laser irradiation to achieve eutectic bonding. The laser beam provides localized heating that melts the solder material, enabling complete contact between electrodes and conductive balls without requiring excessive pressure or large electrode areas. This substitution of mechanical action with optical/thermal energy resolves the contradiction by achieving reliable bonding through a different physical mechanism.
Solution Approach 2:
The patent changes the bonding parameters by introducing laser irradiation with specific wavelength (500-1300 nm) and controlling the substrate transmittance. By adjusting the laser parameters and substrate optical properties, the bonding process achieves complete contact with smaller electrode areas, thus improving bonding yield while reducing chip area.
2Reliability
If the area of chip electrode is increased to ensure complete contact with conductive balls, then the bonding yield is improved, but the electrode area becomes larger
Solution Approach 1:
The patent replaces mechanical pressing with laser-induced eutectic bonding. The laser energy locally melts the solder material at the bonding interface, creating complete contact between electrodes and conductive balls without requiring large electrode areas. This mechanism achieves high bonding yield with minimized electrode dimensions.
Solution Approach 2:
The patent introduces laser energy as an intermediary to facilitate the bonding process. The laser beam acts as a mediator that transfers energy to the solder material, enabling eutectic melting and complete contact formation. This intermediary approach allows precise control of the bonding process with small electrode areas while maintaining high bonding yield.
3Ease of manufacture
If conventional bonding methods are used, then the bonding process is simple, but the connection yield decreases due to incomplete contact
Solution Approach 1:
The patent replaces conventional mechanical bonding methods with laser-induced eutectic bonding. This substitution maintains relative process simplicity while dramatically improving connection yield through localized melting and complete contact formation. The laser bonding process eliminates the need for complex mechanical pressing equipment and achieves superior bonding results.
Solution Approach 2:
The patent utilizes the phase transition of solder material from solid to liquid state through laser heating. This phase transition enables complete contact between electrodes and conductive balls, significantly improving connection yield. The controlled melting and subsequent solidification create reliable bonds without complicating the manufacturing process.
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 enhances the bonding yield between electronic components and substrates by utilizing the transmittance characteristics of the substrate and eutectic bonding with laser irradiation, enabling smaller electrode and pad areas while maintaining effective contact, thus improving production efficiency.
Implementation Method 1
The substrate defines a thickness less than or equal to 100 μm. The substrate further defines a plurality of transmittances, and at least one of the transmittances is greater than 20% under the condition of a wavelength of light being between 500 nm and 1300 nm
Implementation Method 2
The at least one electrode of each electronic component is eutectic bonded to one of the connection pads
Implementation Method 3
Each of the electronic components includes at least one electrode arranged on a face thereof facing towards the substrate. The at least one electrode of each electronic component is eutectic bonded to one of the connection pads
Data Source
AI summary
An electronic device includes a substrate, a trace layer and a plurality of electronic components. The substrate defines a thickness less than or equal to 100 µm. The substrate further defines a plurality of transmittances, and at least one of the transmittances is greater than 20% under the condition of the wavelength of light being between 500 nm and 1300 nm. The trace layer is arranged on the substrate, and the trace layer includes a plurality of connection pads. The electronic components are arranged on the substrate. Each electronic component is provided with at least one electrode, which is arranged on a face of the electronic component facing the substrate. At least one electrode of each electronic component is eutectic bonded to one of the connection pads.