Flip-Chip Interconnect Vibration for Void-Free Underfilling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fine-pitch semiconductor devices face solderability issues due to inclusion of foreign particles and voids in the contact interface between chip bumps and substrate pads, leading to non-uniform stress distribution and reliability problems, especially with thermoset polymer underfills containing inorganic filler particles.
Innovation Solution
Mechanical vibration of one member relative to the other during the approach, with displacements at right angles to the direction of contact, expels foreign particles and residues from the contact areas, allowing for intimate surface contact and reliable solder connections without voids or suspended particles, using a non-conductive polymer paste with 60-70% silica fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-attach method with non-conductive polymer paste is used to enable fine-pitch underfilling, then underfilling capability is improved, but foreign particles and voids are included in the contact interface
Solution Approach 1:
The patent applies mechanical vibration during the bump-to-pad contact process to expel foreign particles and voids from the contact interface. The vibration causes the viscous polymer paste to move dynamically, allowing suspended particles to be ejected from the contact area as the bump approaches and contacts the pad, thereby achieving clean intimate contact while maintaining the benefits of pre-attach underfilling
2Reliability
If mechanical vibration is applied during contact to expel foreign particles, then contact reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements mechanical vibration as a relatively simple auxiliary process during the attachment step. The vibration mechanism can be integrated into the existing assembly equipment, adding minimal complexity while significantly improving contact reliability by eliminating foreign particles and voids from the contact interface
3Device complexity
If capillary forces alone are used for underfilling, then process simplicity is maintained, but uniform filling is insufficient in fine-pitch devices
Solution Approach 1:
The patent applies mechanical vibration during the underfilling process to enhance the capillary flow of the viscous polymer paste into the fine-pitch gaps. The vibration prevents air entrapment and ensures uniform filling of the stand-off region, achieving complete and consistent underfilling without requiring complex additional equipment or processes
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 method ensures reliable contact and underfilling of the stand-off between chip and substrate in fine-pitch devices, reducing thermomechanical stress and enabling mass production with small force, gentle on low-k dielectrics, and eliminating the need for expensive equipment like vacuum suction.
Implementation Method 1
Mechanical vibration of one member relative to the other during the approach, with displacements at right angles to the direction of contact, expels foreign particles and residues from the contact areas
Implementation Method 2
The low viscosity precursor is pulled into gap by capillary forces, leaving a meniscus of about 0.5 mm around the chip perimeter
Data Source
AI summary
Attaching a semiconductor chip to a substrate by applying mechanical vibrations (150) to a polymeric compound (130) and the contacting areas (114, 124) of a first (113) and a second (121) metallic member immersed in the compound, while the two metallic members approach (140) each other until they touch. The mechanical vibration causes displacements of the first member relative to the second member, and the vibration includes displacements (150) oriented at right angles to the direction (140) of the approach. The polymeric compound (130) includes a non-conductive adhesive resin paste (NCP) and filler particles; the paste is deposited before the attaching step. The first member (113) is affixed to the chip and the second member (121) to the substrate.