Thermocompression Solder Bump Deformation for Semiconductor Assembly
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Solution Overview
Problem
Current semiconductor chip assembly processes are complex and not suitable for high-volume manufacturing, particularly in forming a reliable temporary mechanical join between chips and substrates using solder bumps before underfill material application.
Innovation Solution
A method involving thermocompression of solder bumps on semiconductor chips and substrate pads at a temperature above room temperature but below the liquid formation point, followed by underfill material application and subsequent heating for metallurgical bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bumps are heated to cause reflow and form a metallurgical join, then reliable bonding is achieved, but the process becomes complex and unsuitable for high-volume manufacturing
Solution Approach 1:
The patent segments the bonding process into two distinct stages: (1) thermocompression bonding to form a temporary mechanical join suitable for high-volume manufacturing, and (2) subsequent reflow heating to create the final metallurgical bond. This segmentation allows each stage to be optimized independently, resolving the contradiction between reliability and process complexity.
Solution Approach 2:
The patent applies preliminary thermocompression bonding before the final reflow heating step. This preliminary action creates a temporary mechanical join that holds the semiconductor chip to the substrate during assembly, enabling high-volume manufacturing while preserving the option to achieve reliable metallurgical bonding in a subsequent step.
2Volume of stationary object
If underfill material is dispensed after solder bump reflow, then gap filling is achieved, but underfill material may penetrate between solder bumps compromising the joint
Solution Approach 1:
The patent performs thermocompression bonding as a preliminary action before dispensing underfill material. This creates a temporary mechanical join with sufficient structural integrity to prevent underfill penetration, while still allowing gap filling to occur. The preliminary bonding step ensures joint integrity is maintained during the underfill dispensing process.
3Strength
If compression force is applied at room temperature, then solder bump deformation is limited, but adequate mechanical contact with pads is not achieved
Solution Approach 1:
The patent changes the temperature parameter during thermocompression bonding, applying compression force at elevated temperatures above room temperature. This temperature increase enhances solder bump deformability, allowing adequate mechanical contact with pads to be achieved through compression. The parameter change resolves the contradiction between mechanical contact strength and processing temperature.
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 simplifies the assembly process, ensures effective mechanical bonding without underfill penetration, and facilitates efficient metallurgical bonding of solder bumps, enhancing the reliability of the semiconductor package assembly.
Implementation Method 1
applying a compression force to the semiconductor chip to cause the solder bumps to deform against, and make contact with, the substrate pads and the semiconductor chip pads, the compression force being applied while the semiconductor chip and substrate are held at a temperature above room temperature
Implementation Method 2
applying a compression force to the semiconductor chip to cause the solder bumps to deform against, and make contact with, the substrate pads
Implementation Method 3
heating the assembled semiconductor chip and substrate to an elevated temperature to cause the solder bumps to melt and reflow
Implementation Method 4
heating the assembled semiconductor chip and substrate to an elevated temperature to cause the solder bumps to melt and reflow and form a plurality of metallurgical bonds
Implementation Method 5
the compression force being applied while the semiconductor chip and substrate are held at a temperature above room temperature and below a temperature at which any liquid will form in at least one of the solder bumps
Data Source
AI summary
An assembly of a semiconductor chip having pads to a substrate having pads aligned to receive the semiconductor chip is provided, whereby at least one of the semiconductor chip pads and substrate pads include solder bumps. The solder bumps are deformed against the substrate pads and the semiconductor chip pads, whereby an underfill material is applied to fill the gap between the semiconductor chip and substrate. The underfill material does not penetrate between the deformed solder bumps, the semiconductor chip pads, and the substrate pads. At least one of the solder bumps have not been melted or reflowed to make a metallurgical bond between the semiconductor chip pads and the substrate pads, and at least another one of the solder bumps have been melted or reflowed to make a metallurgical bond between the semiconductor chip pads and the substrate pads.