Low Melting Solder TSV for Popcorn Cracking Prevention
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Solution Overview
Problem
Conventional semiconductor packages face challenges in preventing cracking during reflow processes due to water vapor expansion, particularly in larger packages where pre-baking is required to prevent popcorn cracking, and there is a need for effective moisture management to ensure package integrity.
Innovation Solution
The implementation of a semiconductor package with a through silicon via (TSV) and a low melting temperature solder, where the solder and solder pad configuration allows contaminants and water vapor to pass through when heated, preventing popcorn cracking and ensuring a tight seal, using a glass lid and a ball grid array, with a melting temperature of the solder below 105°C and a maximum heating temperature of 260°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solder mask or similar material is used as the cavity wall in wafer level packaging, then the package structure is simple and manufacturing is easier, but the package is prone to cracking during reflow process and requires pre-baking to prevent popcorn cracking
Solution Approach 1:
The invention changes the material parameter of the cavity wall from conventional solder mask to a specialized coating material that can withstand reflow temperatures without cracking. This material parameter change eliminates the need for pre-baking while maintaining package integrity, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The invention uses a composite structure with a specialized coating material on the cavity wall that combines the benefits of ease of manufacture with enhanced thermal stability. This composite approach allows the package to withstand reflow temperatures without cracking, eliminating the need for pre-baking while maintaining structural integrity.
2Reliability
If pre-baking is performed to prevent popcorn cracking during reflow, then package integrity is improved, but manufacturing process complexity and time increase
Solution Approach 1:
The invention applies a specialized coating material to the cavity wall in advance during manufacturing, which provides inherent protection against popcorn cracking during reflow. This preliminary action eliminates the need for separate pre-baking steps, reducing manufacturing process complexity while maintaining package integrity.
Solution Approach 2:
The specialized coating material acts as a sacrificial protective layer that prevents cracking during reflow. This disposable protective mechanism eliminates the need for complex pre-baking processes, simplifying manufacturing while ensuring package integrity.
3Reliability
If thicker silicon is used to prevent popcorn cracking during testing, then package reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the protective mechanism from increasing silicon thickness to applying a specialized coating material on the cavity wall. This parameter change maintains package integrity while avoiding the manufacturing complexity and cost associated with thicker silicon substrates.
4Object-affected harmful factors
If the package is heated above the melting temperature of low melting temperature solder, then contaminants and water vapor can escape through the solder, but the solder may compromise the hermetic seal
Solution Approach 1:
The invention introduces a two-layer solder structure with a low melting temperature sacrificial layer and a high melting temperature hermetic layer. The sacrificial layer acts as an intermediary that allows contaminant escape during heating, while the hermetic layer maintains seal integrity, resolving the contradiction between contaminant removal and hermetic seal preservation.
Solution Approach 2:
The solder structure is segmented into two functional layers: a low melting temperature sacrificial layer for contaminant escape and a high melting temperature hermetic layer for seal integrity. This segmentation allows each layer to perform its specific function without compromising the other, enabling both contaminant removal and hermetic sealing.
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
This solution effectively prevents popcorn cracking and ensures moisture management by allowing contaminants to escape during heating, maintaining package integrity and meeting high moisture sensitivity level requirements for automotive applications.
Implementation Method 1
The low melting temperature solder may melt before 105° C.
Implementation Method 2
The low melting temperature solder and the solder pad may be configured to allow contaminants and water vapor to pass through
Implementation Method 3
allow contaminants to escape during heating
Implementation Method 4
sealing the one or more solder pads in a cavity through coupling a glass lid to the first side of the wafer
Data Source
AI summary
Implementations of semiconductor packages may include: a wafer having a first side and a second side, a solder pad coupled to the first side of the wafer, a through silicon via (TSV) extending from the second side of the wafer to the solder pad a metal layer around the walls of the TSV, and a low melting temperature solder in the TSV. The low melting temperature solder may also be coupled to the metal layer. The low melting temperature solder may couple to the solder pad through an opening in a base layer metal of the solder pad.