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Method for electrolytic plating without a plating bar for a one-sided electronic circuit substrate

IP.com Disclosure Number: IPCOM000007713D
Publication Date: 2002-Apr-16
Document File: 8 page(s) / 44K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for electrolytic plating without a plating bar for a one-sided electronic circuit substrate. Benefits include improved manufacturability and improved performance.

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Method for electrolytic plating without a plating bar for a one-sided electronic circuit substrate

Disclosed is a method for electrolytic plating without a plating bar for a one-sided electronic circuit substrate. Benefits include improved manufacturability and improved performance.

Background

      One-sided electronic circuits are inflexible in their routing capability. As a result, a plating-bar is required on the circuit to plate the metals such as nickel, gold, silver, tin, palladium and solder (see Figure 1).

      Conventionally, electro-less plating does not require a plating bar to plate metal onto copper. However, plating the metal thick enough is difficult with an electro-less plating process, and it is difficult to control compared to the electrolytic plating process.

              The conventional semi-additive technique can also be used to solve this problem by creating a build-up structure. Metal is directly plated on the current feeding medium. Electroplating is limited to the top surface of the copper trace because the copper trace is sandwiched by patterning resist materials. Copper traces must be made by the additive process, increasing the number of process steps.

General description

      Disclosed is a method for electrolytic plating the copper trace of a one-sided electronic circuit substrate using a thin conductive layer on the backside of the circuit as a current feeding medium. This method plates a layer without placing a plating-bar on the circuit. By eliminating the plating-bar, a high-density circuit pattern can be achieved.

              The key elements of the method include the following:

§         Current-feeding layer is laid on the backside of the circuit as an alternative to the plating bar. This layer consists of thin copper plated by electro-less plating or laminated conductive thin film. It is removed completely by etching or peeling.

§         Current is fed to the circuit from the backside of the substrate through a blind via that can be formed anywhere.

§         Plating metal does not touch the current feeding medium, because the current feeding layer is on the backside of circuit and is not exposed to the circuit surface.

§         Metal layers can be electroplated not only on the top surface of copper trace but also on the copper trace side.

 


Advantages

      The disclosed method provides advantages, including:

§         The plating-bar is eliminated from the circuit.

§         A high-density circuit can be achieved because no signal routing inhibition occurs.

§         No requirement exists to use the semi-additive technique and electro-less plating process, so a cost effective and stable process can be achieved.

Detailed description

      Disclosed is a method for fabricating the electrolytic plating layer on a copper trace of a one-sided electronic circuit substrate (see Figure 2). An alternative current-feeding layer is utilized to remove the plating-bar from the circuit (see Figure 3). Advantageously, a high-density circuit substrate can be designed.

      A base film (see Figure 4, 120) that has an adhesive lay...