Flip Chip Electroforming for Thermal and Alignment Control
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Solution Overview
Problem
Conventional encapsulation methods for flip chips, such as eutectic, solder paste, and electromagnetic pulse-weld bonding, face challenges including high costs, limited reliability, poor thermal conductivity, and stress on the chip due to alignment inaccuracies and cutting processes, which hinder the widespread adoption of high-power flip-LED technology.
Innovation Solution
An encapsulation method involving electroforming metal on the electrode surfaces of flip chips and encapsulation substrates, using photoetching and metal conducting films to ensure precise connection and alignment, thereby improving positional accuracy and thermal dissipation while reducing stress on the chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If electromagnetic pulse-weld bonding method is used, then thermal conductivity is improved, but alignment accuracy between chip electrode and substrate electrode deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-plating metal conducting films on both the chip electrode and substrate electrode surfaces before the bonding process. This preparatory step ensures that the electroforming process can proceed with high precision, achieving both excellent thermal conductivity and alignment accuracy without the drawbacks of electromagnetic pulse-weld method.
Solution Approach 2:
The patent replaces the electromagnetic pulse-weld bonding mechanism with an electroforming-based bonding approach. This substitution allows for better control over the bonding process, enabling simultaneous achievement of high thermal conductivity through metal interconnection and high alignment accuracy through controlled electroforming growth, while avoiding the alignment sensitivity issues of electromagnetic pulse-weld method.
2Reliability
If laser cutting is used to cut metal substrate, then electrical connection between electrodes is cut off, but stress on the chip increases
Solution Approach 1:
The patent extracts the metal substrate from the bonding process entirely, replacing it with an organic encapsulation substrate. This eliminates the need for laser cutting operations that cause stress to the chip, while still achieving electrical isolation between electrodes through the inherent insulating properties of the organic substrate and photoresist patterns.
Solution Approach 2:
The patent introduces an organic encapsulation substrate as an intermediary material between the chip and the external environment. This substrate provides both mechanical support and electrical isolation without requiring cutting operations, thereby protecting the chip from stress while maintaining electrical isolation between electrodes.
3Strength
If eutectic bonding method is used, then bonding strength is improved, but production cost increases
Solution Approach 1:
The patent employs inexpensive, readily available materials such as organic encapsulation substrates, photoresist, and common metals (copper, nickel, gold) for the electroforming process. This approach replaces expensive eutectic bonding materials and processes with cost-effective alternatives that achieve comparable or superior bonding strength through electroforming metal growth.
Solution Approach 2:
The patent changes the bonding mechanism from thermal eutectic bonding to electroforming-based bonding. This parameter change allows for controlled metal growth that creates strong bonds between chip and substrate, while using inexpensive materials and simpler equipment, thereby reducing production cost while maintaining bonding strength.
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 method enhances positional accuracy, simplifies the process, improves production efficiency, and effectively reduces thermal resistance, making it suitable for high-power flip chips by ensuring reliable and efficient heat dissipation.
Implementation Method 1
plating a metal conducting film on the electrode surface of the flip chip and the surface of the encapsulation substrate
Implementation Method 2
electroforming metal on an electrode surface of a flip chip and a surface of an encapsulation substrate simultaneously, to realize a connection between an electrode of the flip chip and the encapsulation substrate through the metal
Implementation Method 3
aligning an electrode structure on a photoetching plate with an electrode structure of the flip chip on a photoetching machine and performing photoetching
Data Source
AI summary
An encapsulation method for a flip chip that includes electroforming metal on an electrode surface of a flip chip and a surface of an encapsulation substrate simultaneously. The encapsulation method specifically includes setting an encapsulation substrate around a flip chip; plating a metal conducting film on an electrode surface of the flip chip and a surface of the encapsulation substrate; coating a photoresist on a surface of the metal conducting film; aligning and photoetching an electrode structure on a photoetching plate and an electrode structure of the flip chip, and covering an insulating part between electrodes with the photoresist; taking the metal conducting film as the electrode, electroforming metal inside the photoresist structural model; and removing the photoresist covering the insulating part and removing the metal conducting film. The encapsulation method adopts electroforming and photoetching technology, and thus the process is simplified and the production efficiency is improved.