Coreless Wiring Board Flatness via Preliminary Solder Resist

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Solution Overview

Problem

The challenge is to maintain the rigidity and flatness of wiring boards formed using the build-up method, especially after removing the support board, which affects the insulation reliability and accuracy of solder resist layer formation, particularly for high-density and high-integrated semiconductor chips.

Innovation Solution

A method involving the formation of a first solder resist layer on a support board, followed by electrode formation, an insulating layer, and a second solder resist layer, with the support board being removed to create a coreless structure, allowing for thin-sized and high-density wiring while ensuring excellent flatness and accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the support board is removed to achieve thin-sized formation, then the thickness is reduced, but the rigidity is reduced making subsequent working difficult

Engineering Contradiction:

ImprovethicknessVSAvoidrigidity

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The solder resist layer is formed on the build up layer while the support board is still present, before the support board is removed. This preliminary action allows the solder resist layer to be formed on a flat surface with adequate rigidity support, avoiding the need to handle and work on the fragile coreless structure later

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of removing the support board first and then forming the solder resist layer (which would require handling the fragile coreless structure), the invention inverts the sequence by forming the solder resist layer first while the support board provides structural support

Inventive Principle:

Principle #13The other way round (Inversion)

2Volume of moving object

If the solder resist layer is formed after removing the support board, then the thin-sized formation is achieved, but the flatness is insufficient reducing working accuracy

Engineering Contradiction:

ImprovethicknessVSAvoidaccuracy of working

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The solder resist layer formation is performed as a preliminary action while the support board is still in place to provide flatness and rigidity. This ensures high working accuracy for the solder resist layer before the support board is removed to achieve the final thin-sized structure

Inventive Principle:

Principle #10Preliminary action

3Volume of moving object

If the build up layer surface is exposed, then the thin-sized formation is achieved, but the insulation reliability deteriorates due to high water absorbing performance

Engineering Contradiction:

ImprovethicknessVSAvoidinsulation reliability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The support board is removed (taken out) from the structure to achieve thin-sized formation and coreless structure. The build up layer is designed to function independently without the support board, with the solder resist layer providing the necessary protection against water absorption and insulation degradation

Inventive Principle:

Principle #2Taking out (Extraction)

4Manufacturing precision

If the support board is kept to maintain rigidity, then the working accuracy is improved, but the thin-sized formation is prevented

Engineering Contradiction:

Improveaccuracy of workingVSAvoidthickness

Core Design Contradiction:

Manufacturing precisionVSVolume of moving object

Solution Approach 1:

The solder resist layer formation is performed as a preliminary action while the support board provides rigidity and flatness for accurate working. After this preliminary working is completed with high accuracy, the support board is then removed to achieve the final thin-sized formation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The manufacturing process is segmented into two distinct phases: Phase 1 with the support board for accurate working, and Phase 2 without the support board for thin-sized formation. This segmentation allows each phase to optimize for its specific requirement without compromising the other

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9155195B2Wiring board and semiconductor device

Publication Date: 2015.10.06 SHINKO ELECTRIC IND CO LTD

AI summary

A method of fabricating a wiring board includes forming a resist layer, such as a solder or plating resist layer, defining an opening portion on a support board such that a portion of the support board is exposed. An electrode is formed directly on the support board within the opening portion, and the plating resist layer, when used, is removed. An insulating layer is formed on the electrode, as well as the support board or solder resist layer, and a wiring portion connected to the electrode at the insulating layer is also formed. A solder resist layer having an opening portion is then formed on the wiring portion, and the support board is removed to expose a surface of the electrode or a surface of the electrode and insulating layer. Another solder resist layer having an opening portion may then be formed on the exposed surface of the insulating layer.