Laser Singulation of Mold Compound Substrates Without Edge Thermal Damage
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Solution Overview
Problem
Conventional methods for singulating integrated circuit (IC) packages, such as diamond sawing, face limitations like edge chipping, edge cracks, copper smear, and high costs, while laser sawing introduces thermal damage and material burning, necessitating an improved method for polymer resin mold compound substrates that ensures uniform singulation at high speed without edge thermal effects.
Innovation Solution
A system utilizing dual focused pulsed laser beams with a galvanometer scanner and F-theta lens, combined with a buffer station and cooling mechanisms, including a heating element and gas injection, to perform high-speed laser ablation along trenches in a cutting jig, ensuring precise and efficient singulation with minimal thermal impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If diamond sawing is used for singulation, then cutting can be performed, but edge chipping, edge cracks, copper smear, and high costs occur
Solution Approach 1:
The patent replaces the mechanical diamond saw system with a laser-based system. The laser beam melts and vaporizes the epoxy mold compound without mechanical contact, eliminating edge chipping, edge cracks, and copper smear that are characteristic of mechanical cutting. The laser energy is focused on the material to be removed, and the molten material is ejected through a nozzle, achieving clean cuts without mechanical stress on the edges.
Solution Approach 2:
The patent changes the cutting parameters by using controlled laser power, pulse duration, and scanning speed. By adjusting these parameters, the laser selectively melts and removes the epoxy mold compound while preserving the underlying copper lead frame and semiconductor die. The controlled parameter changes enable precise singulation without the harmful effects of mechanical cutting.
2Ease of operation
If laser sawing is used for singulation, then no tool wear and non-contact process are achieved, but thermal damage and material burning occur
Solution Approach 1:
The patent uses pulsed laser operation instead of continuous laser exposure. The laser emits short pulses at controlled intervals, allowing the material to cool between pulses. This periodic action prevents excessive heat accumulation that would cause thermal damage and material burning, while still achieving effective singulation through cumulative material removal.
Solution Approach 2:
The patent introduces a gas flow (inert gas or air) as an intermediary between the laser beam and the workpiece. This gas flow serves multiple functions: it cools the molten material, prevents oxidation, and assists in ejecting the melted epoxy from the cut zone. The gas mediator carries away excess heat and prevents thermal damage to the surrounding areas.
3Productivity
If high-speed laser ablation is used for singulation, then throughput is improved, but debris removal becomes challenging
Solution Approach 1:
The patent employs a pneumatic system using compressed gas flow to remove debris from the cut zone. The gas flow is directed through a nozzle positioned near the laser focal point, creating a strong气流 that rapidly ejects melted and vaporized epoxy debris from the singulation area. This pneumatic debris removal system operates simultaneously with the high-speed laser ablation, preventing debris accumulation even at high cutting speeds.
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 enables fast and consistent singulation of polymer resin mold compound substrates with reduced edge defects and thermal damage, achieving higher throughput and maintaining a narrower scribe line, thus overcoming the limitations of traditional methods.
Implementation Method 1
laser ablation to remove debris
Implementation Method 2
Heat generated by lasers is often a significant concern
Implementation Method 3
cooling mechanisms, including a heating element and gas injection
Data Source
AI summary
The invention includes a system and method of using a laser for singulation of a polymer resin mold compound substrate into packages or chips by a laser ablation process. A metal jig used for holding the substrate includes trenches to allow the laser beam to penetrate during cutting. Built-in piping allows water to circulate in a base around the jig to cool the substrate during cutting. The laser beam can pass through a cutting nozzle along with compressed gas or air to cool the substrate and remove debris. A pulsed laser beam can be split into two beams for dual focal spots used in the high speed cutting process, so that a combination of passes at different speeds and laser parameters can be achieved. This allows single pass singulation of units at high speed.