Circuit Board Redistribution Structure for Bridge-Free Surface Treatment

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Solution Overview

Problem

The manufacturing of circuit boards with fine spaces is challenging due to bridge issues and electrical short circuits during the surface treatment process, especially after the temporary carrier is removed.

Innovation Solution

A circuit board structure design featuring a thin film redistribution layer with a first dielectric layer having openings that expose pads, where the first dielectric layer's surface is higher than the pads, acting as a dam to prevent electrical short circuits, and a surface treatment layer with varying thicknesses to enhance structural reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the pad size and pad pitch are decreased to increase the number of I/Os, then the product functionality and performance are improved, but the manufacturing precision and reliability deteriorate due to bridge issues and electrical short circuits

Engineering Contradiction:

Improvenumber of I/OsVSAvoidsurface treatment process precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The pad structure is segmented into multiple layers: the original pad on the carrier, the thin film redistribution layer with its own pads, and the surface treatment layer. This segmentation allows each layer to serve specific functions and reduces the risk of short circuits between adjacent pads.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution transitions from a two-dimensional pad arrangement to a three-dimensional structure by adding vertical layers (thin film redistribution layer, dielectric layers, surface treatment layer). This enables increased I/O density without proportionally decreasing pad pitch, as pads are separated in the vertical dimension.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If the pad pitch is decreased to increase I/O density, then the product integration is improved, but the reliability deteriorates due to bridge issues after temporary carrier removal

Engineering Contradiction:

ImproveI/O densityVSAvoidelectrical short circuit prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The thin film redistribution layer with its pad structure and dielectric layers is formed on the temporary carrier before the carrier is removed. This preliminary structure provides mechanical support and electrical isolation during the critical carrier removal process, preventing bridge issues before they can occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The thin film redistribution layer acts as an intermediary between the temporary carrier and the final circuit board structure. It provides the necessary mechanical support and electrical isolation during the transition from temporary carrier to final product, preventing direct contact between adjacent pads that would cause short circuits.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If the surface treatment process is performed after temporary carrier removal, then the carrier interference is eliminated, but the manufacturing difficulty increases due to bridge issues

Engineering Contradiction:

Improvecarrier removalVSAvoidsurface treatment process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The thin film redistribution layer, dielectric layers, and pad structures are all formed on the temporary carrier before the surface treatment process. This preliminary formation simplifies the subsequent surface treatment process by providing a stable, pre-structured substrate that doesn't require complex carrier management during treatment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of performing surface treatment on the carrier and then removing the carrier (which causes bridge issues), the invention inverts the sequence by forming the complete thin film structure on the carrier first, then removing the carrier, and finally performing surface treatment on the now-independent thin film structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12369250B2Circuit board structure and manufacturing method thereof

Publication Date: 2025.07.22 UNIMICRON TECH CORP

AI summary

A circuit board structure includes a carrier, a thin film redistribution layer disposed on the carrier, solder balls electrically connected to the thin film redistribution layer and the carrier, and a surface treatment layer. The thin film redistribution layer includes a plurality of pads, a first dielectric layer, a first metal layer, a second dielectric layer, a second metal layer, and a third dielectric layer. A plurality of first openings of the first dielectric layer expose part of the pads, and a first surface of the first dielectric layer is higher upper surfaces of the pads. The solder balls are disposed in a plurality of third openings of the third dielectric layer and are electrically connected to the second metal layer and the carrier. The surface treatment layer is disposed on the upper surfaces, and a top surface of the surface treatment layer is higher than the first surface.