Vacuum Boat Reflow Bonding for IC Package Warpage Control
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Solution Overview
Problem
The packaging of integrated circuits faces issues with warpage due to differing Coefficients of Thermal Expansion (CTEs) between device dies and package substrates, leading to irregular joints and bump cracks during the reflow process, which adversely affects the yield of the packaging process.
Innovation Solution
A vacuum boat system is used, featuring a base with a thermal insulation layer and air-penetration layer with holes, creating a vacuum environment that flattens the package substrate and maintains a controlled pressure to prevent warpage, allowing for precise bonding of package components during the reflow process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic materials are used as dielectric materials in package substrates for easy lamination, then ease of manufacture is improved, but warpage occurs due to elevated temperatures during solder reflow
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the package substrate through vacuum application. By creating a vacuum environment during the reflow process, the substrate is pulled flat against the support surface, counteracting the warpage that would otherwise occur due to thermal expansion of organic dielectric materials during solder reflow.
2Adaptability or versatility
If device dies and package substrates have significantly different Coefficients of Thermal Expansion (CTEs), then adaptability to different materials is improved, but warpage is worsened during bonding
Solution Approach 1:
The patent implements preliminary anti-action by applying vacuum pressure before and during the reflow process to preemptively counteract the warpage forces that arise from CTE mismatch. The vacuum creates a holding force that maintains substrate flatness throughout the thermal cycling process, preventing the irregular joints and bump cracks that would result from uncontrolled warpage.
3Manufacturing precision
If vacuum pressure is applied to flatten package substrates, then manufacturing precision is improved, but device cracking may occur
Solution Approach 1:
The patent applies dynamics by making the vacuum pressure application conditional and time-dependent. The vacuum is applied specifically during the reflow process when warpage occurs, and is released afterward. This dynamic control ensures substrate flatness is maintained only when needed during bonding, while avoiding continuous vacuum exposure that could cause device cracking.
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 vacuum boat system effectively reduces warpage and improves the reliability of the packaging process by maintaining a stable environment for bonding, ensuring consistent and reliable connections between package components and substrates.
Implementation Method 1
A vacuum boat system is used, featuring a base with a thermal insulation layer and air-penetration layer with holes, creating a vacuum environment that flattens the package substrate and maintains a controlled pressure to prevent warpage
Implementation Method 2
A vacuum boat system is used, featuring a base with a thermal insulation layer and air-penetration layer with holes
Data Source
AI summary
A method includes placing a first package component over a vacuum boat, wherein the vacuum boat comprises a hole, and wherein the first package component covers the hole. A second package component is placed over the first package component, wherein solder regions are disposed between the first and the second package components. The hole is vacuumed, wherein the first package component is pressed by a pressure against the vacuum boat, and wherein the pressure is generated by a vacuum in the hole. When the vacuum in the hole is maintained, the solder regions are reflowed to bond the second package component to the first package component.