Embedded Circuit Pattern Fabrication via Imprinting
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Solution Overview
Problem
Conventional methods for fabricating printed circuit boards (PCBs) face challenges in achieving high density and reliability, particularly with finer circuit patterns, as they tend to separate from the insulating layer, leading to reduced adhesivity and increased fabrication costs due to complex processes like Laser Patterning Process (LPP) that require additional polishing and expensive equipment.
Innovation Solution
A build-up process combined with a simple imprinting process is used to form an embedded circuit pattern, minimizing separation and reducing lead time and fabrication costs, while also forming bump pads with uniform diameter and height for improved electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional semi-additive process is used to form circuit patterns, then the circuit pattern can be formed with fine lines, but the circuit pattern separates from the insulating layer due to reduced contact area
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on the insulating layer before forming the circuit pattern. This protrusion structure is prepared in advance to increase the contact area between the circuit pattern and insulating layer, preventing separation issues that would occur with fine circuit patterns on flat surfaces.
2Reliability
If LPP (Laser Patterning Process) is used to form embedded circuit patterns, then separation is prevented, but the process requires additional polishing and expensive equipment, increasing lead time and cost
Solution Approach 1:
The patent uses a mold for the imprinting process that can be easily fabricated and replaced. This mold-based approach avoids the need for expensive laser patterning equipment while achieving the same embedded circuit pattern formation. The mold is a simple, cost-effective tool that enables the process to be performed with standard fabrication equipment.
Solution Approach 2:
The patent replaces the laser-based patterning process with a mechanical imprinting process. Instead of using laser energy to ablate and form patterns, a physical mold is pressed into the photoresist layer to create the embedded circuit pattern structure, eliminating the need for expensive laser equipment and additional polishing steps.
3Quantity of substance
If the circuit pattern is made finer to increase density, then the density increases, but the contact area with insulating layer is reduced, weakening adhesivity
Solution Approach 1:
The patent introduces a vertical dimension to the insulating layer by forming a protrusion that extends upward. This dimensional change creates an elevated surface that increases the contact area with the circuit pattern in the vertical direction, compensating for the reduced horizontal contact area that occurs when circuit patterns are made finer for increased density.
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
The solution effectively reduces separation issues, shortens fabrication time, and lowers costs by embedding the circuit pattern and forming bump pads with superior conductive properties, enabling better electrical connections and achieving fine pitches.
Implementation Method 1
an electroless plating layer 18 is formed on both the insulating layer 12 and the inner wall of the via hole 16. The electroless plating process functions as a pretreatment procedure of a subsequent electroplating process
Implementation Method 2
the electroplating layer 24 is formed in both the opening 22 and the via hole 16
Data Source
AI summary
Disclosed is a printed circuit board, which includes an insulating member having a circuit pattern embedded in one surface thereof, a bump pad formed in the insulating member so as to be connected to the circuit pattern and protruding from an outer surface of the insulating member, a build-up layer formed on one surface of the insulating member and including a build-up insulating layer and a circuit layer formed in the build-up insulating layer and having a via connected to the circuit pattern, and a solder resist layer formed on the build-up layer. A method of fabricating the printed circuit board is also provided. The printed circuit board is fabricated using a build-up process and the outermost circuit layer thereof is formed to have an embedded structure using an imprinting process, thus minimizing the separation of the circuit layer and reducing the lead time and the fabrication cost.