Thermal Compression Bonding for Solder Bump Integrity
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Solution Overview
Problem
Conventional bonding processes in integrated circuit manufacturing often result in cracking of solder bumps and increased risk of shorting due to the expansion of solder bumps during the reflow process, leading to inefficiencies and higher costs.
Innovation Solution
A thermal compression bonding process using a substrate carrier with work piece holders and a heating tool that applies simultaneous heat and pressure to solder bumps on multiple work pieces, preventing collapse and ensuring uniform bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reflow process is used to bond chip to package substrate, then bonding is achieved, but solder bumps collapse and crack due to weight and thermal expansion
Solution Approach 1:
The patent applies preliminary action by performing compression bonding before the reflow process. The chip is compressed onto the package substrate with controlled force to establish initial contact and alignment of solder bumps, preventing collapse during subsequent reflow. This preliminary mechanical bonding ensures solder bumps maintain their shape and position throughout the thermal cycling process.
Solution Approach 2:
The patent changes the parameters of the bonding process by introducing controlled compression force and maintaining it throughout reflow. Instead of allowing free thermal expansion, the system applies sustained pressure that counteracts the natural tendency of solder bumps to collapse and crack, thereby maintaining manufacturing precision while achieving reliable bonding.
2Reliability
If solder bumps are heated during reflow, then bonding is achieved, but spacing between bumps decreases causing shorting risk
Solution Approach 1:
The compression process is performed preliminarily to establish proper spacing and alignment of solder bumps before reflow heating begins. This preliminary mechanical constraint prevents thermal expansion from causing bump migration and shorting, while still allowing the bonding to occur during reflow.
Solution Approach 2:
The patent changes the thermal and mechanical parameters by applying controlled compression force during the entire reflow process. This sustained pressure counteracts thermal expansion effects, maintaining adequate spacing between solder bumps and preventing shorting while still achieving reliable bonding through the combined thermal-mechanical process.
3Reliability
If conventional sequential bonding is used, then individual chips are bonded one by one, but throughput is low and costs are high
Solution Approach 1:
The patent merges multiple individual bonding operations into a single parallel process. Multiple chips are placed on the package substrate simultaneously and subjected to the same compression and reflow process together. This combining of operations maintains bonding quality through uniform process conditions while dramatically increasing throughput by processing multiple units in one cycle.
Solution Approach 2:
The bonding apparatus is designed with multi-functionality to handle multiple chips simultaneously. The compression system and reflow chamber serve universal purposes for all chips on the substrate at once, rather than requiring separate dedicated processes for each chip, thereby improving productivity without sacrificing bonding quality.
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 process significantly improves throughput and reduces costs by allowing simultaneous bonding of multiple chips, minimizing the risk of solder bump shorting and maintaining even bump heights and sizes, thereby enhancing the reliability and efficiency of the bonding process.
Implementation Method 1
A thermal compression bonding (TCB) process is provided
Implementation Method 2
A thermal compression bonding process using a substrate carrier with work piece holders and a heating tool that applies simultaneous heat and pressure to solder bumps on multiple work pieces, preventing collapse
Data Source
AI summary
A method includes providing a substrate carrier including work piece holders, and placing a first plurality of work pieces into the work piece holders. A second plurality of work pieces is picked up and placed, with each of the second plurality of work pieces being placed on one of the first plurality of work pieces. Solder bumps between the first and the second plurality of work pieces are then reflowed to simultaneously bond the first and the second plurality of work pieces together.