Semiconductor Package Laser Reflow for Low-Warpage PoP Bonding
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing wafer warpage and achieving consistent bonding in Package-on-Package (PoP) technology due to global heating methods, which can lead to defects like cold joints and solder bridging, and limit manufacturing flexibility and throughput.
Innovation Solution
A multi-shot reflow process using a laser beam to locally heat package components, where each laser shot overlaps and partially overlaps package regions, reducing indirect heating of the bottom component and allowing for controlled heating parameters to minimize warpage and improve bonding consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If global heating methods are used to bond package components, then bonding can be achieved across the entire wafer, but wafer warpage increases and defects like cold joints and solder bridging occur
Solution Approach 1:
The patent applies local quality by transitioning from global heating to localized laser heating. The laser beam is directed at specific regions of the top package component, heating only the areas where bonding is needed. This localized approach prevents excessive thermal expansion and warpage of the entire wafer while achieving consistent bonding at the target locations, thereby resolving the contradiction between bonding consistency and wafer shape stability.
Solution Approach 2:
The patent segments the heating process by dividing the wafer into multiple regions and heating them sequentially or selectively using laser shots. Instead of applying heat uniformly across the entire wafer surface, the laser targets specific bond regions individually. This segmentation allows precise control of thermal input, preventing cumulative thermal stress that causes warpage while ensuring reliable bonding in each segmented region.
2Productivity
If global heating methods are used, then entire wafers can be processed simultaneously, but manufacturing flexibility and throughput are limited due to defects
Solution Approach 1:
The patent introduces dynamics by making the heating process adaptive and controllable. The laser system can dynamically adjust heating parameters such as power, duration, and positioning based on real-time requirements. This allows the manufacturing process to be flexible - it can bond entire wafers when needed for high throughput, or selectively bond only specific regions when flexibility is required, thereby resolving the contradiction between productivity and adaptability.
Solution Approach 2:
The patent applies parameter changes by allowing independent control of heating parameters for different regions and time points. The laser processing parameters (power, speed, pulse duration) can be varied to optimize bonding for different package types, materials, and production volumes. This parametric control enables the system to adapt between high-volume production mode and low-volume customized bonding, achieving both high productivity and manufacturing flexibility.
3Manufacturing precision
If indirect heating of the bottom package component occurs, then thermal energy is distributed throughout the structure, but wafer warpage is exacerbated and bonding precision is reduced
Solution Approach 1:
The patent extracts the harmful indirect heating effect by using laser heating that directly targets the top package component and bond interfaces. The laser energy is absorbed at the specific bonding locations without significant thermal diffusion to the bottom package component. This extraction of indirect heating prevents the thermal blooming that causes warpage and maintains precise bonding control, thereby improving manufacturing precision while reducing energy loss to unnecessary heating.
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 multi-shot reflow process effectively reduces wafer warpage, enhances bonding consistency, and eliminates defects such as cold joints and solder bridging, while increasing manufacturing flexibility and throughput by allowing selective heating of package components.
Implementation Method 1
performing a first laser shot on a first portion of a top surface of the first package component, the first laser shot reflowing the first conductive connector
Implementation Method 2
the first laser shot reflowing the first conductive connector of the first region
Implementation Method 3
heat generated by the laser beam being transferred through the first package component to the conductive material
Data Source
AI summary
In an embodiment, a method includes: aligning a first package component with a second package component, the first package component having a first region and a second region, the first region including a first conductive connector, the second region including a second conductive connector; performing a first laser shot on a first portion of a top surface of the first package component, the first laser shot reflowing the first conductive connector of the first region, the first portion of the top surface of the first package component completely overlapping the first region; and after performing the first laser shot, performing a second laser shot on a second portion of the top surface of the first package component, the second laser shot reflowing the second conductive connector of the second region, the second portion of the top surface of the first package component completely overlapping the second region.