Dummy Patterns in Fan-Out Packages to Control Underfill Bleeding
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Solution Overview
Problem
Integrated fan-out packages face challenges in preventing underfill material from bleeding or creeping onto the chip backside during the underfill dispensing step, leading to increased bleeding length and reduced production efficiency.
Innovation Solution
The use of dummy patterns and an optional dam structure over a redistribution layer, which are designed to constrain the underfill material and prevent it from reaching undesired bumps, thereby reducing bleeding length and enhancing capillary attraction for faster dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill material is dispensed during the underfill dispensing step, then the micro-bumps are surrounded and protected, but the underfill material bleeds or creeps onto the chip backside, increasing bleeding length and reducing production efficiency
Solution Approach 1:
The patent divides the dispensing area into two distinct zones: a first area where underfill material is dispensed to surround micro-bumps, and a second area (chip backside) where underfill material is prevented from reaching. The dummy patterns act as boundaries that segment the flow path, allowing controlled dispensing in the first area while blocking migration to the second area.
Solution Approach 2:
Dummy patterns are introduced as intermediary structures between the underfill material and the chip backside. These dummy patterns serve as a mediator that intercepts and contains the underfill material, preventing direct contact with undesired bumps on the chip backside while still allowing the underfill to perform its protective function around the micro-bumps.
2Reliability
If underfill material is dispensed to surround micro-bumps, then reliability is improved, but underfill bleeding length increases and dispensing time increases
Solution Approach 1:
The dummy patterns are formed in advance on the substrate before the underfill dispensing step. This preliminary action creates pre-defined barriers that guide and constrain the underfill material flow during dispensing, eliminating the need for extended dispensing time to achieve proper containment and reducing the bleeding length that would otherwise require additional time to manage.
3Productivity
If dummy patterns are added to constrain underfill material, then bleeding length is reduced and dispensing efficiency is improved, but device complexity increases
Solution Approach 1:
The dummy patterns are designed with specific geometric parameters (size, shape, spacing, and positioning) that are optimized to provide effective underfill constraint. By carefully controlling these parameters, the dummy patterns achieve maximum containment efficiency with minimal structural complexity, allowing standard dispensing processes to be used without requiring complex additional components.
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 dummy patterns significantly reduce underfill bleeding length, widen the underfill dispensing window, and improve production efficiency by shortening the underfill dispensing time and increasing wafer per hour (WPH) output.
Implementation Method 1
enhancing capillary attraction for faster dispensing
Data Source
AI summary
Integrated fan-out packages and methods of forming the same are disclosed. An integrated fan-out package includes a first chip, a redistribution layer structure, a plurality of connection pads, a plurality of dummy patterns, a plurality of micro-bumps, a second chip and an underfill layer. The redistribution layer structure is electrically connected to the first chip. The connection pads are electrically connected to the redistribution layer structure. The dummy patterns are at one side of the connection pads. The micro-bumps are electrically connected to the connection pads. The second chip is electrically connected to the micro-bumps. The underfill layer covers the plurality of dummy patterns and surrounds the micro-bumps.