Semiconductor Chip Stack Mounting Thermal Interference
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Solution Overview
Problem
In semiconductor device manufacturing, the heat transfer from permanently crimping one chip stack can cause undesirable thermal changes, such as premature curing of the non-conductive film (NCF) or melting of bumps, in adjacent chip stacks, leading to bonding failures when chip stacks are closely packed on a substrate with high thermal conductivity.
Innovation Solution
A method involving a temporary crimping step followed by a permanent crimping step, where chip stacks are formed in a temporarily crimped state with a specified separation distance to prevent heat transfer-induced thermal changes, ensuring that chip stacks under permanent crimping are separated enough to avoid thermal interference, and a map is created to determine optimal formation positions based on the separation distance and mounting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chip stacks are closely packed on a substrate to increase mounting density, then productivity and area utilization are improved, but heat transfer from permanent crimping causes premature curing of NCF or melting of bumps in adjacent chip stacks
Solution Approach 1:
The substrate surface is divided into multiple mounting regions with designated separation distances between chip stack formation positions. This segmentation allows heat from permanent crimping of one chip stack to dissipate before affecting adjacent chip stacks, preventing premature NCF curing or bump melting while maintaining high mounting density through optimized spatial arrangement.
Solution Approach 2:
The formation positions of chip stacks are predetermined and specified in advance based on thermal conductivity characteristics of the substrate and permanent crimping conditions. By pre-calculating and specifying separation distances that prevent thermal interference, the system ensures that adjacent chip stacks will not be adversely affected during permanent crimping while maximizing area utilization.
2Reliability
If permanent crimping is performed on one chip stack at a time, then thermal interference with adjacent chip stacks is avoided, but the number of process steps increases and manufacturing efficiency decreases
Solution Approach 1:
The substrate is divided into multiple independent mounting regions with specified separation distances between them. This allows permanent crimping to be performed on multiple chip stacks simultaneously or in sequence without thermal interference, as each region is thermally isolated from others. The segmentation maintains bonding quality while enabling parallel processing to reduce overall manufacturing complexity.
Solution Approach 2:
The optimal formation positions and separation distances are predetermined based on substrate thermal conductivity and crimping parameters. This preliminary specification allows the manufacturing system to efficiently plan and execute permanent crimping operations across multiple chip stacks without needing to perform sequential single-stack processing, thereby reducing the total number of process steps while ensuring bonding quality.
3Temperature
If the substrate has high thermal conductivity to improve heat dissipation, then thermal management is improved, but heat from permanent crimping transfers more efficiently to adjacent chip stacks causing thermal damage
Solution Approach 1:
The substrate surface is segmented into distinct mounting regions with specified separation distances between chip stack positions. This segmentation leverages the high thermal conductivity of the substrate by allowing heat to dissipate laterally into the surrounding substrate area rather than transferring vertically to adjacent chip stacks. The separation distance ensures that heat from one chip stack does not reach the NCF or bumps of neighboring stacks, maintaining both effective heat management and prevention of thermal damage.
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 prevents undesirable thermal changes in adjacent chip stacks during the permanent crimping process, ensuring proper bonding between semiconductor chips and the substrate by maintaining the NCF in a non-cured state and bumps in a solid form until the intended crimping temperature is reached.
Implementation Method 1
the NCF reversibly softens with a temperature rise below a predetermined curing start temperature
Implementation Method 2
the NCF irreversibly cures with a temperature rise above the curing start temperature
Implementation Method 3
the heat applied to one chip stack for the permanent crimping is transferred to other chip stacks in the temporarily crimped state in the vicinity
Implementation Method 4
the bumps of all of the plurality of semiconductor chips forming the chip stack are melted
Data Source
AI summary
The disclosure is provided with: a temporary crimping step in which one or more semiconductor chips 10 are sequentially laminated while being temporarily crimped in each of two or more locations on a substrate 30 to thereby form chip stacks ST in a temporarily crimped state; and a permanent crimping step in which the top surfaces of all of the chip stacks ST formed in the temporarily crimped state are sequentially heated, pressurized, and permanently crimped. Furthermore, a specifying step is provided prior to the temporary crimping step for specifying a separation distance Dd which is the distance from the chip stacks ST under permanent crimping to a location at which the temperature of the substrate 30, the temperature having been raised by heating for the permanent crimping, becomes less than or equal to a prescribed permissible temperature Td, and in the temporary crimping step, the chip stacks ST in the temporarily crimped state are formed separated from each other by the separation distance Dd or more.