Semiconductor Solder Bump Composition Control via Layered Deposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solder bump plating processes face challenges in composition control, particularly with tin-copper solder, where variations in copper content can lead to unexpectedly high melting temperatures, exceeding the thermal limits of circuit board and semiconductor chip components, potentially preventing solder liquification.
Innovation Solution
A method involving the deposition of layers of metallic materials with specific desired volumes of tin and copper, followed by reflow to form solder structures with precise composition ratios, avoiding bulk plating of pre-combined solder constituents and ensuring controlled copper content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bulk plating of pre-mixed solder solution is used, then the plating process is simple, but the solder composition cannot be precisely controlled leading to unpredictable melting temperatures
Solution Approach 1:
The solder bump fabrication process is segmented into distinct deposition steps: first depositing a copper layer to a first thickness, then depositing a tin layer to a second thickness. This segmentation allows independent control of each metal layer's thickness, enabling precise control of the final solder composition and melting temperature.
Solution Approach 2:
The copper layer is deposited first as a preliminary action before the tin layer. By establishing the copper base layer first and then controlling the tin deposition thickness, the process pre-determines the solder composition parameters before the actual soldering operation, ensuring predictable melting characteristics.
2Reliability
If copper content in tin-copper solder varies, then the solder can still conduct current, but the melting temperature may significantly exceed desired reflow temperatures
Solution Approach 1:
The process incorporates feedback control through precise thickness measurements of deposited layers. By monitoring and controlling the copper layer thickness (first thickness) and tin layer thickness (second thickness), the system feedback-adjusts the deposition parameters to maintain the desired solder composition within tight tolerances, ensuring melting temperature remains within the safe reflow range.
Solution Approach 2:
The invention changes the critical parameter of solder composition by independently controlling the thickness parameters of copper and tin layers. By adjusting the first thickness (copper) and second thickness (tin) parameters during deposition, the process optimizes the solder's melting temperature to match the reflow profile requirements while maintaining electrical conductivity.
3Strength
If high copper content solder is used, then the solder joint strength may improve, but the melting temperature increases beyond circuit board tolerance
Solution Approach 1:
The invention applies local quality control by optimizing the copper distribution specifically at the interface region through controlled copper layer deposition. The copper layer is deposited to a specific first thickness to provide adequate interfacial bonding and joint strength, while the tin layer deposited to a second thickness controls the overall melting temperature, creating a composition gradient that satisfies both strength and thermal safety requirements locally.
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 approach allows for the formation of solder bumps with a desired composition, preventing overheating and ensuring reliable solder liquification, thus maintaining the integrity of temperature-sensitive components.
Implementation Method 1
The first and second layers are reflowed to form a solder structure with a desired ratio of the first metallic material to the second metallic material
Implementation Method 2
a solder bump is metallurgically bonded to a given I/O site or pad of the semiconductor chip and a so-called pre-solder is metallurgically bonded to a corresponding I/O site of the circuit board
Data Source
AI summary
Various semiconductor chip solder bump and underbump metallization (UBM) structures and methods of making the same are disclosed. In one aspect, a method is provided that includes depositing a layer of a first metallic material on a semiconductor chip. The first layer has a first physical quantity. A layer of a second metallic material is deposited on the layer of the first metallic material. The second layer has a second physical quantity. The first and second layers are reflowed to form a solder structure with a desired ratio of the first metallic material to the second metallic material.