Chip Substrate Heat Bonding via Pre-heating and Light Pulse
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Solution Overview
Problem
Current methods for bonding chips to substrates, such as reflow oven soldering and photonic heat bonding, often damage flexible substrates with low damage temperatures due to high temperatures and energy requirements, and are inefficient or costly, especially in roll-to-roll processes.
Innovation Solution
A method involving pre-heating the substrate to an elevated temperature below its damage threshold, followed by a light pulse to the chip to momentarily increase its temperature and transfer heat to the bonding material, allowing for bonding without exceeding the substrate's damage temperature, thereby reducing heat drain and risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reflow oven soldering is used to bond chip to substrate, then bonding strength is improved, but substrate damage occurs due to prolonged exposure to temperatures above the damage temperature
Solution Approach 1:
The substrate is pre-heated to an elevated temperature (e.g., 80-150°C) before the light pulse is applied. This preliminary heating reduces the temperature difference between substrate and chip, minimizing heat drain from the chip to the substrate during bonding, thereby preventing substrate damage while still achieving sufficient bonding strength
Solution Approach 2:
A short-duration light pulse (e.g., 1-100 milliseconds) is applied to the chip to momentarily increase its temperature above the bonding temperature. This periodic, pulsed heating allows the chip to transfer sufficient heat to the bonding material for strong bonding, while the brief duration prevents excessive heat accumulation that would damage the substrate
2Productivity
If photonic heat bonding with high intensity light pulse is used, then bonding speed is improved, but substrate damage occurs due to high energy exposure
Solution Approach 1:
The substrate is pre-heated before the high intensity light pulse is applied. This reduces the energy required from the light pulse to achieve bonding, as the substrate is already close to the bonding temperature, thereby preventing substrate damage while maintaining fast bonding speed
Solution Approach 2:
The method changes the temperature parameters dynamically: the substrate is maintained at an elevated temperature (e.g., 80-150°C) while the chip is momentarily heated to a higher temperature (e.g., 150-250°C) during the light pulse. This parameter differentiation allows fast bonding while protecting the substrate from damage
3Use of energy by moving object
If laser spot soldering is used to bond chip to substrate, then energy consumption is reduced, but positioning complexity increases due to small spot area
Solution Approach 1:
The flash lamp provides a broad illumination area that can bond multiple chips or large areas of the substrate in a single pulse, making the system universal and eliminating the need for precise positioning of individual spots, thereby reducing positioning complexity while maintaining low energy consumption
Solution Approach 2:
Instead of using a single focused laser spot, the flash lamp creates multiple illumination points simultaneously across the substrate, effectively copying the bonding action across multiple locations at once, which reduces the need for repeated positioning operations
4Productivity
If flash lamp photonic soldering is used, then bonding efficiency is improved, but substrate damage occurs due to high intensity illumination
Solution Approach 1:
The substrate is pre-heated to an elevated temperature before the flash lamp pulse is applied. This preliminary action reduces the energy requirement of the flash lamp, allowing efficient bonding while preventing substrate damage from excessive intensity
Solution Approach 2:
The flash lamp provides a high intensity pulse that is partially absorbed by the chip and bonding material, while the pre-heated substrate absorbs the remaining energy without damage. The partial action on the pre-heated substrate prevents damage while still achieving efficient bonding
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 enables effective bonding of chips to low-cost, flexible substrates with reduced risk of damage, improved production efficiency, and compatibility with roll-to-roll processing, while minimizing energy requirements and costs.
Implementation Method 1
pre-heating at least the substrate from an initial temperature to an elevated temperature
Implementation Method 2
applying a light pulse to the chip to momentarily increase the temperature of the chip to a pulsed peak temperature
Implementation Method 3
the momentarily increased pulsed peak temperature of the chip causes a flow of conducted heat from the chip to the bonding material
Data Source
AI summary
A method and system for heat bonding a chip to a substrate by means of heat bonding material disposed there between. At least the substrate is preheated from an initial temperature to an elevated temperature below a damage temperature of the substrate. A light pulse applied to the chip momentarily increases the chip temperature to a pulsed peak temperature below a peak damage temperature of the chip. The momentarily increased pulsed peak temperature of the chip causes a flow of conducted heat from the chip to the bonding material, causing the bonding material to form a bond.