Removable Lid for IC Reflow Warpage Control
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Solution Overview
Problem
The warpage of substrates during the reflow process in bonding integrated circuit (IC) packages to printed circuit boards (PCBs) causes alignment issues and prevents proper connection, and the use of copper lids to mitigate warpage interferes with cooling, creating a thermal gradient.
Innovation Solution
A reversibly connected lid with a spring-loaded piston applies a force perpendicular to the substrate to reduce warpage, and is removed after a second reflow process to allow cooling, using interlocking features and epoxy-based adhesives for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a copper lid is used to mitigate substrate warpage during reflow process, then substrate alignment is improved, but cooling of the IC die is interfered with creating a thermal gradient
Solution Approach 1:
The lid is segmented into a frame structure with spaced-apart sides rather than a solid copper lid, allowing thermal gradients to develop more freely while still providing structural support to counteract substrate warpage during the reflow process
Solution Approach 2:
The lid is made removable and is discarded after the reflow process completes, allowing the IC die to cool properly without the lid's interference. The lid serves its purpose during heating but is removed before cooling to avoid creating thermal gradients
2Stability of the object's composition
If the lid remains attached during the second reflow process, then substrate warpage is controlled, but the IC die cannot cool sufficiently
Solution Approach 1:
The lid attachment system is made dynamic rather than permanent, allowing the lid to be attached during the reflow process for warpage control and then removed afterward to enable proper cooling of the IC die
Solution Approach 2:
The lid is attached during the heating phase of the reflow process and removed during the cooling phase, creating a periodic attachment-detachment cycle that optimizes both warpage control and thermal management at different stages of the manufacturing process
3Temperature
If a reversible connection mechanism is used for the lid, then the lid can be removed for cooling, but the connection structure becomes more complex
Solution Approach 1:
The connection mechanism is segmented into simple snap-fit features distributed around the perimeter of the lid, rather than a single complex fastening system, enabling reversible attachment while maintaining relative structural simplicity
Solution Approach 2:
The frame acts as an intermediary structure with recesses that receive protrusions from the lid, providing a simple mechanical interface that enables reversible connection without requiring complex fastening mechanisms
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 reduces substrate warpage and ensures proper alignment for bonding while allowing sufficient cooling of the IC die by applying a controlled force and using heat-curable adhesives for secure attachment.
Implementation Method 1
A reversibly connected lid with a spring-loaded piston applies a force perpendicular to the substrate to reduce warpage
Implementation Method 2
using interlocking features and epoxy-based adhesives for secure attachment
Implementation Method 3
using heat-curable adhesives for secure attachment
Data Source
AI summary
One embodiment includes a method for manufacturing an electronic apparatus, including bonding an integrated circuit (IC) die to a substrate to form an IC package using a first reflow process, which causes the substrate to warp, reversibly connecting a lid with the IC package over the IC die so that the lid applies a force to the IC die, providing a printed circuit board (PCB) including an array of first contact pads, respectively disposing an array of bonding elements on an array of second contact pads of the substrate, placing the IC package on to the PCB with respective ones of the bonding elements contacting respective ones of the first contact pads, performing a second reflow process to apply heat to the bonding elements to bond the first contact pads with the second contact pads, and removing the lid from the IC package after the second reflow process.