Wafer Lift and Level Assembly for Fast Die Bond Planarization
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Solution Overview
Problem
Current die bonding systems face challenges in quickly heating and cooling localized areas of a wafer while maintaining precision for dies smaller than 200 um2, minimizing pick error, and ensuring planarity without causing wafer cracking, often requiring multiple planarization procedures and calibration steps.
Innovation Solution
A die bonding system utilizing a wafer lift and level assembly with suction cups, a leveling pedestal, and guide clevises that allows for vertical motion, combined with a heater assembly for localized heating and a focused energy source, enables quick and precise planarization and heating of wafers, reducing the need for multiple planarization procedures and minimizing wafer cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple planarization procedures are performed to ensure wafer planarity, then planarity precision is improved, but processing time increases and productivity decreases
Solution Approach 1:
The wafer is planarized in advance using a leveling pedestal with adjustable feet before the bonding process begins. This preliminary planarization action eliminates the need for repeated planarization procedures during bonding, thereby improving throughput while maintaining precision.
Solution Approach 2:
The planarization function is separated from the bonding process and implemented as an independent preprocessing step using a dedicated leveling pedestal. This segmentation allows planarization to be completed once beforehand, rather than repeatedly during the bonding operation.
2Use of energy by moving object
If focused energy sources are used to heat the substrate from below, then heating efficiency is improved, but thermal shock to the die and substrate increases causing cracking
Solution Approach 1:
A transparent heater assembly is introduced as an intermediary between the focused energy source and the substrate. The heater distributes the thermal energy uniformly across the substrate surface, preventing localized overheating and thermal shock that would cause cracking.
Solution Approach 2:
The heating system provides localized heating control through the transparent heater assembly, which can be positioned to heat specific areas of the substrate uniformly. This localized control prevents excessive heat concentration that causes thermal shock.
3Measurement precision
If a stationary up-facing camera is used to calculate pick error, then pick error is minimized, but the system requires precise calibration that is sensitive to temperature drift
Solution Approach 1:
The mechanical calibration system is replaced with an optical reference system. Fiducial markers on the wafer serve as stable reference points for the camera, eliminating the need for mechanical calibration and making the system immune to thermal drift.
Solution Approach 2:
Fiducial markers are placed on the wafer to create optical copies or references of known positions. The camera captures images of these fiducials to calculate pick error, providing a stable reference system that does not require mechanical calibration.
4Temperature
If the bond head heats the die to reflow temperatures, then localized heating precision is improved, but the substrate temperature remains ambient limiting bonding options
Solution Approach 1:
The heating function is segmented into two independent systems: the bond head heats the die from above with precise localization, while the transparent heater assembly heats the substrate from below. This segmentation allows both die and substrate to be heated independently, providing bonding process flexibility.
Solution Approach 2:
The transparent heater assembly enables the substrate to be heated to various temperatures for different bonding processes (epoxy, solder, etc.), while the bond head maintains its precision heating capability. This multi-functionality increases bonding process versatility.
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 system achieves rapid and precise planarization and heating of wafers, reducing pick errors and wafer cracking, while allowing for efficient die bonding operations with localized support and controlled heating, thus enhancing production efficiency.
Implementation Method 1
The wafer frame is configured to secure a wafer disposed therein
Implementation Method 2
a heater assembly for localized heating
Implementation Method 3
a focused energy source, enables quick and precise planarization and heating of wafers
Data Source
AI summary
A die bonding system comprising a wafer lift and level assembly configured to allow rapid planarization of a wafer comprising a wafer frame configured to retain a wafer and be slidably retained within guide clevises and a leveling pedestal configured to support a wafer from below in a localized area where a die bonding operation is to take place, allowing the quick and repeatable planarization of die(s) to the wafer without the need for distinct planarization procedures that would slow cycle times and decrease production.