Flip-Chip Underfill Resin Penetration via Vacuum and Pressure Cycling
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Solution Overview
Problem
In flip-chip assembly, the underfill resin struggles to penetrate deeply between the semiconductor chip and substrate due to increased propagation resistance at small pitches and spacings, leading to void formation, which reduces stress relaxation and bond integrity, and compromises moisture protection.
Innovation Solution
The method involves supplying underfill resin in a vacuum atmosphere and then exposing it to atmospheric pressure, using a heated epoxy resin with low viscosity to facilitate deep penetration and minimize voids, ensuring reliable bonding and moisture protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch of electrodes and bumps is reduced to increase integration level, then the integration level improves, but the propagation resistance of underfill resin increases making deep penetration difficult
Solution Approach 1:
The patent applies preliminary action by heating the underfill resin before injection to reduce its viscosity. This pre-heating treatment enables the resin to penetrate deeply into the narrow spaces between closely-spaced electrodes and bumps, overcoming the propagation resistance caused by small pitch dimensions while maintaining high integration levels.
Solution Approach 2:
The patent changes physical parameters of the underfill resin by controlling temperature and viscosity. By heating the resin to appropriate temperatures before injection and maintaining specific viscosity characteristics, the resin achieves adequate flow properties to penetrate deep into the assembly gaps despite the small electrode pitch, thus resolving the contradiction between high integration and resin penetration.
2Quantity of substance
If the number of electrodes is increased to improve integration, then the integration level improves, but void formation in underfill resin increases
Solution Approach 1:
The patent applies preliminary action by pre-heating the underfill resin to reduce viscosity before injection. This enables the resin to flow smoothly and completely fill the spaces between numerous electrodes, preventing air entrapment and void formation even when the electrode count reaches 400 or more, thus maintaining reliability alongside high integration.
Solution Approach 2:
The patent changes the viscosity parameter of the underfill resin through temperature control. By optimizing the resin's viscosity characteristics and injection temperature, the resin achieves adequate flowability to completely saturate the assembly gaps in high-electrode-count configurations, eliminating voids and ensuring reliable stress distribution across all solder bumps.
3Quantity of substance
If the spacing between chip and substrate is reduced to improve integration, then the integration level improves, but the propagation resistance of resin increases leading to insufficient penetration
Solution Approach 1:
The patent applies preliminary action by heating the underfill resin before injection to significantly reduce its viscosity. This pre-heating enables the resin to penetrate through the reduced 15 μm or smaller spacing between chip and substrate, overcoming the high propagation resistance that would otherwise prevent adequate filling in such tight configurations.
Solution Approach 2:
The patent changes the physical state and viscosity parameters of the underfill resin through temperature control. By maintaining the resin at elevated temperatures during injection, the resin achieves low enough viscosity to flow through the narrow 15 μm gaps, ensuring complete penetration and void-free filling despite the reduced spacing that corresponds to high integration levels.
4Reliability
If voids form in the underfill resin, then the stress relaxation ability is reduced, but bond breakage risk increases
Solution Approach 1:
The patent changes the viscosity parameter of the underfill resin through temperature control and material selection. By optimizing the resin's flow characteristics, the resin completely fills the assembly gaps and encapsulates all solder bumps, eliminating voids that would otherwise compromise both stress relaxation ability and bond strength, thus simultaneously maintaining both reliability and strength.
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 reduces void formation, enhances bonding reliability, and improves moisture protection by ensuring the underfill resin penetrates deeply between the chip and substrate, thereby increasing the connection strength and reliability of the flip-chip assembly.
Implementation Method 1
the underfill resin moves deep into this space due to capillary action to seal the solder bumps between the semiconductor chip and the substrate
Implementation Method 2
an underfill resin is supplied between the principal surface of the semiconductor chip and the substrate in a vacuum atmosphere
Implementation Method 3
the semiconductor chip and substrate with said supplied underfill resin are exposed to atmospheric pressure
Data Source
AI summary
The objective of the invention is to provide a semiconductor device manufacturing method that can suppress the formation of voids in the underfill resin and realize a highly reliable flip-chip assembly. The semiconductor device manufacturing method pertaining to the present invention comprises the following processing steps: a step of operation in which a plurality of electrodes 24, formed in a two-dimensional array on a principal surface 22 of semiconductor chip 20, are connected to corresponding conductive regions 32, 34 on substrate 30, a step of operation in which underfill resin 40 is supplied between the principal surface of the semiconductor chip and the substrate, and a step of operation in which the semiconductor chip and substrate with supplied underfill resin 40 are exposed to atmospheric pressure.