WCSP Light-Blocking Coating With Narrow-Lane Laser Dicing
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Solution Overview
Problem
Existing wafer-level chip scale package (WCSP) processes for semiconductor dies, particularly those with light-sensitive circuitry, face challenges in applying light-blocking coatings efficiently, leading to increased costs and reduced wafer area utilization due to the need for reconstituted wafers and mechanical sawing, which are costly and inefficient.
Innovation Solution
A method involving trench formation, light-blocking material deposition, and laser or plasma dicing to apply a light-blocking coating to all six sides of semiconductor dies, allowing for narrower scribe lanes and reducing mechanical sawing, thereby enhancing efficiency and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick mold compound coating is applied to block light transmission through die sides, then light blocking effectiveness is improved, but the spacing required between devices increases and reconstituted wafers are required
Solution Approach 1:
The light blocking function is segmented into two parts: a first light blocking material applied to the device side surface and sides of the die, and a second light blocking material applied to the backside surface. This segmentation allows each material to be optimized for its specific location and function, eliminating the need for a single thick coating that would require excessive spacing.
Solution Approach 2:
The light blocking approach transitions from a single-dimensional thick coating on the sides to a multi-dimensional solution involving coatings on multiple surfaces (device side, sides, and backside). This dimensional approach allows light blocking from multiple directions, preventing light transmission through the die without requiring excessive thickness on any single surface.
2Object-affected harmful factors
If mechanical sawing is used to singulate dies after applying light blocking coating, then light blocking is achieved, but production costs increase and wafer area utilization decreases
Solution Approach 1:
The patent replaces mechanical sawing with laser dicing or plasma dicing methods. These non-mechanical methods can singulate dies through the light blocking materials without requiring the materials to be mechanically removable, thereby improving production efficiency and reducing costs while maintaining effective light blocking.
3Object-affected harmful factors
If reconstituted wafers are used to apply light blocking coating, then light blocking is achieved, but production costs increase and individual die handling is required
Solution Approach 1:
The patent merges the light blocking coating application with the wafer-level processing steps. By applying light blocking materials to entire wafers before singulation, the process combines multiple functions (light blocking, solder bump formation, and die attachment) into a single integrated workflow, eliminating the need for separate reconstitution and individual die handling steps.
Solution Approach 2:
The light blocking materials are applied to the wafers before the dies are singulated and attached to substrates. This preliminary action allows subsequent mechanical or laser dicing to proceed without concern for damaging light blocking coatings, as the coatings are already in place and designed to withstand the dicing process.
4Ease of manufacture
If wider scribe lanes are used to accommodate mechanical sawing, then mechanical dicing is enabled, but wafer area for device production decreases
Solution Approach 1:
The patent substitutes mechanical sawing with laser dicing or plasma dicing methods that can operate with much narrower scribe lanes. This substitution enables effective use of the entire wafer area for device production while still achieving complete singulation of dies through the light blocking materials.
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 enables cost-effective production of semiconductor dies with light-blocking coatings by minimizing mechanical sawing, increasing wafer area utilization, and reducing production costs through laser or plasma dicing, while maintaining effective light blocking.
Implementation Method 1
a laser can be used to form distressed regions in a wafer along the scribe lanes, and the wafer can be singulated by breaking stretching a dicing tape supporting the semiconductor dies to singulate the wafer along the lines of stress
Implementation Method 2
Plasma dicing, which chemically etches through the semiconductor wafer along the scribe lanes, can be used
Data Source
AI summary
A described example includes: a semiconductor die having bond pads on a device side surface, having a backside surface opposite the device side surface and having four sides extending between the device side surface and the backside surface; a layer of light blocking material deposited on the device side surface, the light blocking material also covering the four sides; semiconductor material on the exterior of the light blocking material covering the four sides, the semiconductor material spaced from the semiconductor device die by the light blocking material covering the four sides; a backside coating of light blocking tape covering the backside surface; openings in the layer of light blocking material on the device side surface, the openings exposing under-bump material formed on the bond pads; and terminals that are formed by solder bumps or conductive post connects formed on the under-bump material.