Semiconductor Marking Layer for Laser Symbolization
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Solution Overview
Problem
Conventional methods for symbolizing semiconductor packages, such as inking and laser scribing, face limitations in reducing letter sizes due to fuzziness, smearing, and the risk of damaging wire arch tops in ultra-thin devices, where the laser beam can dig through the thin encapsulation material.
Innovation Solution
A thin sheet with regions of contrasting optical reflectivity and color is attached to the package surface, and pulsed energy is used to alter the reflectivity of specific spots on the sheet, creating the symbolization without altering the surface flatness or causing debris, allowing for smaller and thinner semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser scribing is used to create symbolization on the package surface, then the symbolization becomes legible through reflection difference, but the laser beam can dig through the thin encapsulation material and expose wire arch tops in ultra-thin devices
Solution Approach 1:
The invention separates the symbolization function from the encapsulation material by introducing a dedicated marking layer. This layer is applied only on the top surface where symbolization is needed, while the underlying encapsulation material remains intact and thick enough to protect wire arches. The marking layer acts as an independent segment that carries the symbolization function without compromising the protective function of the encapsulation material.
Solution Approach 2:
The marking layer serves as an intermediary between the laser beam and the encapsulation material. It absorbs the laser energy and undergoes reflectivity changes to create legible symbols, while preventing the laser beam from penetrating through and damaging the wire arches underneath. This intermediary layer enables symbolization without direct laser-m encapsulation material interaction.
2Measurement precision
If inking technique is used for symbolization, then the symbolization becomes legible through color difference, but the deposited ink forms heaps or piles that deviate from the flatness of the package surface
Solution Approach 1:
The invention replaces the mechanical ink deposition process with a laser-based marking process on a thin polymer layer. Instead of physically depositing ink that forms heaps, the laser beam induces chemical or physical changes in the polymer marking layer to create regions of different reflectivity. This substitution eliminates the mechanical pile-up problem while achieving legible symbolization through optical contrast.
Solution Approach 2:
The invention changes the physical-chemical parameters of the marking layer through laser irradiation. The laser beam alters the reflectivity, color, or surface properties of the polymer material in specific patterns, creating legible symbols without adding material volume. This parameter change approach maintains surface flatness while achieving the desired symbolization effect.
3Length of stationary object
If the package compound thickness is reduced to meet smaller and thinner component requirements, then the device size is reduced, but the risk of wire arch top exposure increases when using conventional symbolization methods
Solution Approach 1:
The invention segments the symbolization function from the protective encapsulation structure. By applying a thin marking layer (1-10 μm) on top of the encapsulation material, it enables symbolization without requiring increased overall package thickness. The marking layer is thin enough not to significantly increase device size but sufficient to provide laser absorption and symbolization functionality while protecting the wire arches underneath.
Solution Approach 2:
The invention moves the symbolization function to a separate dimensional layer - a thin surface marking layer applied on top of the encapsulation material. This dimensional separation allows the bulk encapsulation material to maintain its protective thickness for wire arch protection, while the surface marking layer provides the symbolization capability with minimal thickness addition, effectively solving the thickness-protection trade-off.
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 maintains the flatness of the package surface, avoids damage to wire arch tops, and supports the thinness and stackability of semiconductor packages, while enabling batch processing and chip-scale package symbolization.
Implementation Method 1
A pulsed beam of energy is focused on a spot of the bare sheet surface; the pulsed energy is absorbed by the material, thereby altering the first reflectivity of the spot to a second reflectivity different from, and contrasting with, the first reflectivity
Implementation Method 2
the pulsed energy is absorbed by the material, thereby altering the first reflectivity of the spot to a second reflectivity
Data Source
AI summary
The symbolization of a semiconductor device (100) is incorporated in a thin sheet (130) attached to the top of the device, facing outwardly with its bare surface. The material of the sheet (about 1 to 10 μm thick) includes regions of a first optical reflectivity and a first color, and regions (133) of a second optical reflectivity and a second color, which differ from, and contrast with, the first reflectivity and color. Preferred choices for the sheet material include the compound o-cresol novolac epoxy and the compound bisphenol-A, more preferably with the chemical imidazole added to the film material. A preferred embodiment of the invention is a packaged device with a semiconductor chip a (101) connected to a substrate (102); the connection is achieved by bonding wires (111) forming an arch with a top 111a. The chip, the wire arches, and the substrate are embedded in an encapsulation material (120), which borders on the attached top sheet so that the arch tops touch the border (131).