Laser-Assisted Bonding for Semiconductor Die Interconnections
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Solution Overview
Problem
Conventional semiconductor die bonding methods using reflow temperatures cause extensive thermal expansion and shrinkage in circuit boards, leading to cracks and electrical disconnection between the semiconductor die and the circuit board.
Innovation Solution
Laser-assisted bonding method where a laser beam is used to reflow bumps on a semiconductor die, applying localized heat to minimize thermal expansion and shrinkage, with a jig plate and jig bars applied to reduce warpage and enhance pressure distribution, using a continuous-wave or pulsed laser with controlled energy and wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reflow temperature is applied to the circuit board in a reflow process, then the bumps are bonded between the semiconductor die and the circuit board, but extensive thermal expansion and shrinkage occur in the circuit board causing cracks and electrical disconnection
Solution Approach 1:
The patent applies localized heating using a laser beam only to the specific region where the semiconductor die and circuit board need to be bonded, rather than heating the entire circuit board. This localized approach achieves the necessary reflow temperature for bump bonding while minimizing thermal expansion and shrinkage in the rest of the circuit board, thereby preventing cracks and electrical disconnection.
Solution Approach 2:
The patent replaces the conventional thermal reflow process (which uses an oven to heat the entire circuit board) with a laser-based localized heating system. This substitution allows precise control of the heating region and temperature, achieving bump reflow without subjecting the entire circuit board to high temperatures that cause harmful thermal expansion and shrinkage.
2Strength
If conventional reflow process is used, then bumps are bonded, but considerable shrinkage occurs in the circuit board during cooling creating cracks in bumps
Solution Approach 1:
The laser beam is focused only on the bump regions where bonding is required, creating localized melting and reflow without heating the entire circuit board. This ensures the bumps are properly bonded while the rest of the circuit board maintains its dimensional stability during both heating and cooling processes, preventing crack formation.
Solution Approach 2:
The patent uses pulsed laser heating to achieve the reflow process, applying heat in controlled pulses rather than continuous heating. This periodic action allows precise control over the heating and cooling cycles, ensuring proper bump bonding while minimizing thermal stress and dimensional changes in the circuit board that could lead to cracks.
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 improves the reliability of electrical connections by minimizing thermal expansion and shrinkage, maintaining the integrity of the semiconductor die and circuit board, and reduces the required bonding space, enhancing space utilization efficiency.
Implementation Method 1
reflowing the bump by directing a laser beam toward the semiconductor die
Implementation Method 2
The laser beam may heat the semiconductor die near the bump to a temperature in a range of 200 to 350 degrees C.
Implementation Method 3
The laser beam may volatize the flux and make an electrical connection between the bump and the circuit pattern
Data Source
AI summary
Laser assisted bonding for semiconductor die interconnections is disclosed and may, for example, include forming flux on a circuit pattern on a circuit board, placing a semiconductor die on the circuit board where a bump on the semiconductor die contacts the flux, and reflowing the bump by directing a laser beam toward the semiconductor die. The laser beam may volatize the flux and make an electrical connection between the bump and the circuit pattern. A jig plate may be placed on the semiconductor die when the laser beam is directed toward the semiconductor die. Warpage may be reduced during heating or cooling of the semiconductor die by applying pressure to the jig plate. Jig bars may extend outward from the jig plate and may be in contact with the circuit board during the application of pressure to the jig plate. The jig plate may comprise one or more of: silicon, silicon carbide, and glass.