Heat Assisted Flip Chip Bonding Apparatus Warpage Control
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Solution Overview
Problem
Warpage of chips during heat reflow in flip chip bonding can lead to weaker bonding between conductive bumps and pads due to differing material expansion coefficients, potentially causing heat damage to other electronic components on the substrate.
Innovation Solution
A press and cover assembly is used to press the chip while a heating source provides heat for reflow, with the press and cover assembly blocking partial heated light to prevent heat damage and ensuring reliable bonding between the chip and substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chip is heated for reflow bonding, then the conductive bumps can be melted for eutectic bond with pads, but warpage occurs due to different expansion coefficients of materials
Solution Approach 1:
The press and cover assembly applies downward pressure on the chip before and during the heating process to counteract the upward warpage force that will occur due to thermal expansion. This preliminary counter-action prevents the chip from warping during reflow, maintaining proper alignment and bonding strength.
Solution Approach 2:
The system changes the physical state of the conductive bumps by heating them to melting temperature for eutectic bonding. Simultaneously, the press and cover assembly maintains mechanical pressure to compensate for dimensional changes caused by thermal expansion, effectively managing parameter changes during the process.
2Reliability
If a heating source is used to provide heat for reflow, then bonding can be achieved, but other electronic components on the substrate may suffer heat damage
Solution Approach 1:
The cover element is designed with a specific opening pattern that allows heated light to pass through only to the chip area requiring bonding, while blocking heat from reaching other electronic components on the substrate. This creates localized heating quality - high heat intensity where needed, low heat intensity where harmful.
Solution Approach 2:
The press and cover assembly acts as an intermediary between the heating source and the substrate. The cover element selectively transmits and blocks heated light, mediating the heat distribution to protect sensitive components while enabling bonding where required.
3Object-affected harmful factors
If the press and cover assembly blocks partial heated light, then heat damage to other components is prevented, but heat distribution uniformity may be affected
Solution Approach 1:
The cover element is designed with specific opening patterns that create localized heat distribution - allowing full heat transmission to the chip area while blocking heat to surrounding areas. This intentional non-uniform heat distribution protects other components while maintaining adequate heating for 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
The solution effectively prevents heat damage to other electronic components and ensures strong bonding between the chip and substrate by controlling the heat distribution and applying pressure during the reflow process, thereby improving the reliability of the flip chip bonding process.
Implementation Method 1
The heating source is located above the semiconductor assembly and provided to generate a heated light
Implementation Method 2
Each includes an elastic unit and a pressing unit. One end of the elastic unit is connected to the cover element and the other end of the elastic unit is connected to the pressing unit. The pressing unit is provided to press a back surface of the chip
Implementation Method 3
the conductive bumps are heated to be melted by heat flow for eutectic bond of the conductive bumps and pads
Data Source
AI summary
A heat assisted flip chip bonding apparatus includes a semiconductor assembly having a substrate and a chip, a heating source and a press and cover assembly having a cover element and press elements. The chip is disposed above the substrate and includes conductors which contact with conductive pads on the substrate. The heating source is provided to emit a heated light which illuminates the chip via an opening of the cover element. The press elements are located between the cover element and the semiconductor assembly and each includes an elastic unit and a pressing unit. Both ends of the elastic unit are connected to the cover element and the pressing unit respectively, and the pressing unit is provided to press a back surface of the chip.