Flip Chip Laser Bonding with Pressure Mask for Warped Chips
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Solution Overview
Problem
The challenge in bonding flip chip-type semiconductor chips to substrates is the risk of poor contact due to the chips being bent or warped, either due to internal stress or thermal expansion differences between the chip and the substrate.
Innovation Solution
A system for laser bonding of flip chip that includes a supply unit for substrates, a fixing unit for securing the substrate, a laser unit for irradiating a laser beam to melt and solidify solder bumps, a mask with a transmitting portion for infrared rays to ensure uniform heating and pressure on the chips, and a controller to manage the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser bonding method is used to bond flip chip semiconductor chips to substrates, then bonding speed and precision are improved, but the risk of poor contact due to chip bending or warping increases
Solution Approach 1:
The system performs preliminary actions by pre-positioning the mask at the optimal distance from the semiconductor chip surface before laser irradiation begins. The controller automatically adjusts the mask position to ensure uniform pressure distribution across all solder bumps, preventing contact issues before they occur during the high-speed bonding process
Solution Approach 2:
The system incorporates feedback mechanisms where the controller monitors the bonding process in real-time and dynamically adjusts laser parameters and mask positioning based on detected variations in chip position or solder bump contact status, ensuring consistent bonding quality even at high speeds
2Length of moving object
If the semiconductor chip thickness is reduced to several tens of micrometers for compactness, then device miniaturization is achieved, but the chip becomes more prone to bending and warping
Solution Approach 1:
The system changes physical parameters by applying controlled pressure through the mask during laser bonding, which counteracts the inherent bending and warping forces in thin chips. The pressurizing unit adjusts pressure parameters to flatten the chip surface locally at the bonding interface, ensuring stable contact between solder bumps despite the chip's reduced thickness
Solution Approach 2:
The mask serves as an intermediary element between the laser beam and the thin semiconductor chip. It not only transmits the laser energy but also provides mechanical support and uniform pressure distribution to prevent warping of the thin chip during the bonding process
3Manufacturing precision
If the mask is positioned closer to the semiconductor chip for better pressure control, then bonding precision is improved, but the mask may interfere with the laser beam transmission
Solution Approach 1:
The system optimizes the mask's physical parameters, particularly its transparency characteristics in the laser wavelength range. By selecting materials and designing structures that are transparent to the specific laser wavelength used, the mask can be positioned close to the chip for precise pressure control without significantly attenuating the laser beam energy
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 system effectively bonds semiconductor chips to substrates while preventing poor contact of solder bumps, even when the chips are bent or warped, by ensuring precise control over the laser beam and pressure application.
Implementation Method 1
the semiconductor chip is irradiated with a laser beam to transfer energy to the semiconductor chip such that the solder bumps are instantaneously melted
Implementation Method 2
the solder bumps are instantaneously melted and then hardened to thereby bond the semiconductor chip to the substrate
Implementation Method 3
a mask with a transmitting portion for infrared rays to ensure uniform heating and pressure on the chips
Data Source
AI summary
A system for laser bonding of flip chip, and more particularly, to a system for laser bonding of flip chip for bonding a flip chip-type semiconductor chip to a substrate by using a laser beam is provided. According to the system for laser bonding of flip chip of the present disclosure, by performing laser bonding on a substrate while pressurizing semiconductor chips, even semiconductor chips which are bent or likely to bend may be bonded to the substrate without causing poor contact of solder bumps.