B-Stage Conductive Polymer Interconnects for Fine Pitch Reliability
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Solution Overview
Problem
Conventional semiconductor devices face issues with fine pitch interconnects between contact pads on flipchip semiconductor dies, as solder bumps are prone to cracking and delamination during thermal cycling, and high temperatures can cause wafer degradation.
Innovation Solution
A semiconductor device is developed using a b-stage conductive polymer formed over contact pads on the semiconductor die, eliminating the need for solder bumps and wettable contact pads by creating an electrical interconnect structure through the conductive polymer, which is deposited over the die and encapsulant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bumps are used for fine pitch interconnects between contact pads, then electrical connection is achieved, but the bumps are prone to cracking and delamination during thermal cycling
Solution Approach 1:
The patent changes the material parameters from traditional solder bumps to conductive polymer material, which has different thermal expansion properties and bonding characteristics. The conductive polymer maintains electrical conductivity while providing better thermal cycling resistance and eliminating crack formation inherent in rigid solder bumps.
Solution Approach 2:
The invention uses composite material structure where conductive polymer is combined with wettable flux to create an interconnect structure that integrates both mechanical bonding and electrical conductivity functions, replacing the separate bump and pad structure. This composite approach provides improved reliability under thermal stress.
2Ease of manufacture
If high temperature processing is used for bump reflow, then solder bumps are formed, but the wafer is subjected to degradation and damage
Solution Approach 1:
The patent changes the processing temperature parameter from high temperature (reflow above solder melting point) to low temperature processing suitable for conductive polymer deposition. This eliminates thermal degradation of the wafer while still achieving proper formation of the conductive interconnect structure.
Solution Approach 2:
The conductive polymer material serves as a temporary interconnect solution that can be deposited at low temperature, performs its function during assembly, and can be removed or replaced if needed, providing a cost-effective alternative to permanent high-temperature solder joints.
3Stability of the object's composition
If wettable contact pads are formed to contain bump material, then bump stability is improved, but the pads can delaminate from conductive layer
Solution Approach 1:
The patent extracts the wettable contact pad layer from the traditional bump interconnect structure, replacing it with conductive polymer that directly bonds to the contact pad. This eliminates the intermediate wettable pad layer that is prone to delamination while still providing effective material containment and electrical connection.
Solution Approach 2:
The conductive polymer acts as an intermediary material between the contact pad and the interconnect structure, providing both mechanical bonding and electrical conductivity. This mediator eliminates the need for separate wettable pads and reduces delamination risks by creating a more integrated structure.
4Adaptability or versatility
If fine pitch interconnects are implemented with bumps, then I/O terminal count is increased, but the complexity of preventing cracking and delamination increases
Solution Approach 1:
The patent changes the interconnect material parameters to conductive polymer, which enables fine pitch implementation without the cracking and delamination issues of solder bumps. The material's properties allow for higher density interconnects with simpler process control and fewer reliability concerns.
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 provides a reliable and cost-effective fine pitch interconnect without the risks of bump cracking and delamination, enhancing the thermal stability and manufacturing efficiency of semiconductor devices.
Implementation Method 1
A conductive polymer is formed over the contact pads on the semiconductor die
Data Source
AI summary
A semiconductor wafer contains a plurality of semiconductor die with bumps formed over contact pads on an active surface of the semiconductor die. A b-stage conductive polymer is deposited over the contact pads on the semiconductor wafer. The semiconductor wafer is singulated to separate the die. An insulating layer is formed over a carrier with openings formed in the insulating layer. The die is mounted to the carrier with the conductive polymer disposed in the openings of the insulating layer. The conductive polymer is heated to a glass transition temperature to liquefy the conductive polymer to an electrically conductive state. An encapsulant is deposited over the die and insulating layer. The carrier is removed to expose the conductive polymer. An interconnect structure is formed over the die, encapsulant, and conductive polymer. The interconnect structure is electrically connected through the conductive polymer to the contact pads on the die.