Chip Package Stiffener Structure for Reflow Warpage Control
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Solution Overview
Problem
Conventional chip packaging schemes face issues with out-of-plane warpage due to material strength and thermal expansion mismatches, leading to potential solder joint bridging during reflow processing, especially in larger packages.
Innovation Solution
A stiffener with a ring body and support members is secured to the package substrate, circumscribing the IC die and extending below the substrate to provide mechanical support and maintain constant spacing with the PCB, preventing warpage and ensuring stable solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional substrates are used without additional support structures, then the device complexity is low, but warpage occurs due to material strength and thermal expansion mismatches
Solution Approach 1:
A stiffener is introduced as an intermediary component between the package substrate and PCB. The stiffener has a first portion attached to the package substrate and a second portion extending below the substrate that attaches to the PCB, acting as a mediator to prevent warpage without requiring fundamental changes to the substrate or PCB designs.
Solution Approach 2:
The stiffener is divided into two distinct portions: a first portion that attaches to the package substrate and a second portion that extends below and attaches to the PCB. This segmentation allows each portion to be optimized for its specific function while working together to solve the warpage problem.
2Stability of the object's composition
If the package substrate is made thicker to reduce warpage, then substrate flatness improves, but the manufacturing cost and processing time increase
Solution Approach 1:
Instead of making the substrate thicker, the support function is segmented into a separate stiffener component. This allows the substrate to remain thin and maintain its original manufacturing cycle time while the stiffener provides the necessary structural support to prevent warpage.
Solution Approach 2:
The stiffener serves as an intermediary that provides the mechanical support needed to prevent warpage without requiring changes to the substrate thickness or material properties, thereby maintaining the original manufacturing timeline.
3Productivity
If the package size is increased to accommodate more IC dies, then component density improves, but warpage and solder joint bridging risk increase
Solution Approach 1:
The stiffener acts as an intermediary structural element that provides support across large package areas, preventing the substrate from warping during reflow processing. This ensures that solder joints remain properly positioned and prevents bridging, even in large-scale packages with high component density.
Solution Approach 2:
The stiffener is attached to the package substrate before reflow processing to preemptively counteract the warpage forces that will occur during heating. By providing preliminary structural support, it prevents solder joint bridging before the problem can occur during the reflow process.
Data Source
AI summary
An electronic device includes a package substrate having a top surface and a bottom surface. An integrated circuit (“IC”) die is disposed on the top surface of the package substrate. The electronic device also includes a stiffener having a ring body and a plurality of support members. The ring body is secured to the top surface of the package substrate and circumscribes the IC die. The plurality of support members extend from the ring body to below the bottom surface of the package substrate.