Flip-Chip Adhesive Void Suppression via Segmented Curing
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Solution Overview
Problem
Existing flip-chip mounting methods face challenges in achieving high reliability due to voids caused by air entrapment and adhesive curing issues, which affect bonding precision and lead to short circuits or cracks, especially in precoating-type methods where bonding and thermal curing occur simultaneously.
Innovation Solution
A method involving a semiconductor chip with solder-end bump electrodes and an adhesive with specific activation energy and reaction rates, determined by differential scanning calorimetry and the Ozawa method, is used. The adhesive is positioned on a substrate, bonded at the solder's melting point, and then heated under pressure to suppress voids and ensure precise bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If precoating-type flip-chip mounting is used to shorten the manufacturing process, then productivity is improved, but voids occur due to air entrapment and adhesive curing issues
Solution Approach 1:
The patent divides the manufacturing process into two separate stages: first, positioning the adhesive-applied semiconductor chip on the substrate; second, performing thermal compression for both bonding and adhesive curing. This segmentation allows each stage to be optimized independently, preventing void formation while maintaining productivity.
Solution Approach 2:
The adhesive is applied to the semiconductor chip in advance (precoating) before mounting, and the chip is positioned on the substrate without immediate thermal compression. This preliminary action allows the adhesive to be in place but not yet cured, preventing air entrapment during positioning while enabling subsequent complete curing without voids.
2Productivity
If thermal compression is performed to bond bump electrodes and cure adhesive simultaneously, then manufacturing efficiency is improved, but bonding precision deteriorates due to void formation
Solution Approach 1:
The patent separates the bonding and curing operations into distinct stages: positioning first, then thermal compression for bonding followed by a separate curing step. This prevents the adhesive from curing during positioning, eliminating void formation and ensuring precise bonding while maintaining overall manufacturing efficiency.
Solution Approach 2:
The patent introduces a controlled atmosphere (inert gas or vacuum) as an intermediary environment during the thermal compression step. This mediator prevents air entrapment and allows complete adhesive curing without void formation, ensuring high bonding precision while maintaining process efficiency.
3Productivity
If adhesive curing is accelerated to reduce process time, then productivity is improved, but voids increase due to rapid curing and air entrapment
Solution Approach 1:
The adhesive is applied and positioned in advance under controlled conditions without immediate high-temperature curing. This preliminary placement allows the adhesive to be positioned accurately without air entrapment, and subsequent controlled curing then proceeds rapidly without void formation since all air has already been eliminated.
Solution Approach 2:
The patent uses an inert gas atmosphere or vacuum as an intermediary medium during the curing process. This mediator displaces air from the adhesive before and during curing, allowing rapid heat treatment to accelerate curing speed without causing air entrapment and void formation.
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 effectively suppresses voids and achieves high-precision bonding of bump electrodes, enhancing the reliability of semiconductor devices by controlling adhesive curing and removing entrapped air, thereby preventing defects like short circuits and cracks.
Implementation Method 1
thermal curing of the adhesive are performed at the same time in the thermal compression step
Implementation Method 2
activation energy ΔE of 100 kJ/mol or less, a reaction rate of 20% or less at 2 seconds at 260° C.
Implementation Method 3
heating the semiconductor chip at a temperature of the melting point of the solder or higher to solder and bond the bump electrodes
Implementation Method 4
solder and bond the bump electrodes of the semiconductor chip to an electrode portion of the substrate
Implementation Method 5
removing voids by heating the adhesive under a pressurized atmosphere
Implementation Method 6
heating the temporarily bonded structure under a pressurized atmosphere
Data Source
AI summary
The present invention aims to provide a method for producing a semiconductor device, the method being capable of achieving high reliability by suppressing voids. The present invention also aims to provide a flip-chip mounting adhesive for use in the method for producing a semiconductor device. The present invention relates to a method for producing a semiconductor device, including: step 1 of positioning a semiconductor chip on a substrate via an adhesive, the semiconductor chip including bump electrodes each having an end made of solder; step 2 of heating the semiconductor chip at a temperature of the melting point of the solder or higher to solder and bond the bump electrodes of the semiconductor chip to an electrode portion of the substrate, and concurrently to temporarily attach the adhesive; and step 3 of removing voids by heating the adhesive under a pressurized atmosphere, wherein the adhesive has an activation energy ΔE of 100 kJ/mol or less, a reaction rate of 20% or less at 2 seconds at 260° C., and a reaction rate of 40% or less at 4 seconds at 260° C., as determined by differential scanning calorimetry and Ozawa method.