PoP Inkjet Barrier Material for Thermal Adhesive Keep-Out Control
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Solution Overview
Problem
Package-on-package (PoP) architectures face thermal performance limitations due to an air gap between the top and bottom packages, as thermal interface materials spread into through mold interconnect (TMI) joints, and existing solutions like solder resist dams are complex and impractical.
Innovation Solution
A barrier, such as a polymeric material with TiO2 particles, is printed between the packages using ink jet printing to confine thermal adhesives and prevent them from spreading into the TMI region, thereby controlling bondline thickness and improving thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal interface material is disposed between the two packages, then thermal performance is improved, but the material spreads and bleeds into the TMI joints causing solder extrusion
Solution Approach 1:
The patent divides the interface between packages into distinct functional zones using a barrier material printed on the substrate. This barrier segments the thermal interface material containment area from the TMI joint areas, allowing thermal material to be applied without it bleeding into solder joints. The barrier creates a clear spatial separation that maintains both thermal performance and joint integrity.
Solution Approach 2:
The barrier material acts as an intermediary element between the thermal interface material and the TMI joints. This intermediate layer prevents direct contact and interaction between the thermal material and solder joints, blocking the harmful spreading effect while allowing thermal conduction through the designated path.
2Manufacturing precision
If solder resist dams are used to confine thermal interface material, then material spreading is prevented, but complex substrate processing including lithography is required
Solution Approach 1:
The patent replaces the complex mechanical lithography process with a printing-based barrier formation method. Instead of using photolithography to create solder resist dams, the barrier material is directly printed onto the substrate in the desired pattern, simplifying the manufacturing process while achieving the same material confinement effect.
Solution Approach 2:
The patent changes the formation method parameter from lithographic patterning to direct printing. This parameter change transforms a multi-step, complex process into a simpler, more direct approach that achieves equivalent or superior material confinement without requiring lithography equipment or complex substrate processing.
3Manufacturing precision
If solder resist dam is formed during substrate manufacturing, then material spreading is controlled, but it must be formed before ball attach step
Solution Approach 1:
The barrier material is printed onto the substrate in advance, before other assembly steps. This preliminary action establishes the material confinement boundaries early in the manufacturing process, enabling subsequent steps like ball attach and thermal material application to proceed without risk of spreading, while maintaining process flexibility.
Solution Approach 2:
The printed barrier material serves multiple functions: it confines thermal interface material, defines bondline thickness, and protects TMI joints. This multi-functional barrier eliminates the need for separate solder resist dams and other confinement structures, simplifying the overall manufacturing process and increasing productivity.
4Ease of manufacture
If air gap exists between top and bottom packages, then package assembly is simplified, but thermal resistance increases
Solution Approach 1:
The patent applies local quality by creating a barrier-only region in specific areas where TMI joints are located, while allowing thermal interface material to fill the bondline in other areas. This localized approach maintains the air gap simplification where needed while enabling thermal conduction where required, achieving both manufacturing simplicity and thermal performance.
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 barrier effectively reduces thermal resistance and prevents adhesive flow into the TMI region, enhancing the thermal performance and yield of PoP systems by allowing standard packages to be modified post-assembly with precise thermal adhesive placement.
Implementation Method 1
A barrier, such as a polymeric material with TiO2 particles, is printed between the packages using ink jet printing to confine thermal adhesives and prevent them from spreading into the TMI region
Implementation Method 2
controlling bondline thickness and pop adhesive keep out zone
Implementation Method 3
effectively reduces thermal resistance and prevents adhesive flow into the TMI region, enhancing the thermal performance
Data Source
AI summary
Embodiments disclosed herein include electronic packages. In an embodiment, the electronic package comprises a first package, wherein the first package comprises, a first package substrate, a first die over the first package substrate, a first mold layer over the first package substrate and around the first die, and a plurality of through mold interconnects (TMIs) through the first mold layer. The electronic package may further comprise a second package electrically coupled the first package by the TMIs, wherein the second package comprises a second package substrate, a second die over the second package substrate, and a solder resist over a surface of the second package substrate opposite from the second die. In an embodiment, the electronic package may also comprise a barrier between the first package and the second package.