Improved double surface treatment plating method

Abstract

The application discloses an improved double-surface treatment plating omission method, relates to a circuit board preparation process, and aims at the double-process plating omission problem in the prior art. All PADs to be subjected to gold plating treatment are electrically connected to a common point and are electrically connected to a large copper layer of a production board through the common point; after a gold plating process is completed, all electrically connected positions of the common point are damaged, and then nickel-gold plating or nickel-palladium-gold plating treatment is performed. The method has the advantages that the plating omission in subsequent nickel-gold plating or nickel-palladium-gold plating is completely eliminated without affecting the effect of the gold plating process. The technical problem which has been unable to be completely eliminated in the industry can be completely eliminated, the scheme only needs to adjust a copper wire layout mode, no additional process is added, the scheme is simple and efficient, costs are not increased, and unexpected technical effects are achieved.

Description

Technical Field

[0001] This invention relates to circuit board manufacturing processes, and more particularly to a method for improving plating defects in dual-surface treatment. Background Technology

[0002] Dual surface treatment, also known in the industry as dual process, refers to electroplating gold + immersion nickel-gold, or electroplating gold + nickel-palladium-gold. Specifically, for the same piece of product, some PADs undergo electroplating gold, while others undergo immersion nickel-gold or nickel-palladium-gold treatment. Electroplating gold is achieved by connecting electroplating leads and applying an electric current to a plating solution containing nickel and gold ions, depositing a layer of nickel or gold. During production, manufacturers in the industry may find some PADs with incomplete plating, but they are unaware of the principle and mechanism behind this. Common methods to address this problem include increasing the activation treatment time to increase the palladium ion density, adding a dragging tank to the nickel bath, increasing the nickel bath temperature, increasing the nickel bath pH value, and performing plasma cleaning before surface treatment. These methods can only reduce the defect rate, not completely eliminate it.

[0003] Through research conducted by the patent applicant, it was discovered that the cause of plating defects lies in the potential difference. In products with a dual-surface treatment process, before the gold plating leads are cut, all immersion nickel-gold PADs connected to the gold plating leads form a uniform network. Subsequently, during the immersion nickel-gold plating process, a potential difference arises, leading to plating defects, such as… Figure 1 The pads in the white box are all connected to the gold-plated leads, causing all the fixed fingers of the PCS to be missed during the immersion nickel-gold plating process. The gold fingers not connected to the gold-plated leads are all immersion nickel-gold plated. The fingers in the red box area are for the nickel-gold plating surface treatment. During gold plating, conductive leads are required for connection, so each finger is connected to the PNL copper foil to form a network. However, the fingers in the white box area need to be immersion nickel-gold plated, so the fingers are connected together to form a network, causing a potential imbalance and creating a potential difference. The effect of the missed plating is as follows: Figure 2 As shown, the fingers highlighted in red are gold-plated, while the fingers not highlighted in red are not.

[0004] The principle behind potential difference generation: Immersion nickel-gold pads are connected via electroplated gold leads, forming a large copper surface that leads to current flow and potential imbalance. During immersion nickel plating, nickel ions need to capture electrons released by hydrogen ions on the copper surface to reduce and deposit. If the immersion gold pads are connected to the large copper surface via wires, charge will migrate from the pads to the unreacted copper surface due to the charge effect. This significantly reduces the electron density on the surface of the pads to be immersion gold, causing the reaction potential to drop. Nickel ions then cannot obtain enough electrons to complete reduction and deposition, thus preventing subsequent immersion nickel-gold plating and resulting in incomplete plating or excessively thin plating layers. Summary of the Invention

[0005] The purpose of this invention is to provide an improved method for preventing plating defects in dual-surface treatment, thereby solving the problems existing in the prior art.

[0006] The present invention describes a method for improving double-surface plating defects by electrically connecting all PADs to be electroplated with gold to a common point, and electrically connecting them to the large copper layer of the production board through the common point; after the electroplating process is completed, all electrical connections of the common point are destroyed, and then immersion nickel-gold or nickel-palladium-gold treatment is performed.

[0007] The improved double-surface plating method described in this invention has the advantage of completely eliminating plating defects in subsequent nickel-gold or nickel-palladium-gold processes without affecting the electroplating gold process. This completely eliminates a long-standing technical problem in the industry, and the solution only requires adjusting the copper wire layout without adding any extra steps. It is simple, efficient, and cost-effective, achieving unexpected technical results. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the gold finger connection in the existing technology of electroplated plates.

[0009] Figure 2 This is an image showing the effect of plating defects in existing technologies.

[0010] Figure 3 This is a schematic diagram of the electroplated plate gold finger connection method described in this invention.

[0011] Figure 4 This is a diagram illustrating the effect of punching holes for connecting gold fingers on an electroplated plate using the method described in this invention. Detailed Implementation

[0012] The present invention describes a method for improving double-surface plating defects by electrically connecting all PADs to be electroplated with gold to a common point, such as... Figure 3 As shown in the red circle. It is electrically connected to the large copper layer of the production board through the aforementioned common point. After the electroplating gold process, all electrical connections at the common point are destroyed, followed by immersion nickel-gold or nickel-palladium-gold treatment, such as... Figure 4 As shown.

[0013] One way to break a common point is to use a CCD punching method to break the wire.

[0014] Finally, when the entire production board is used for immersion nickel-gold surface treatment of fingers, it is no longer a single network, but rather dispersed into multiple networks, thereby avoiding potential imbalance that could lead to plating defects.

[0015] Through statistical analysis of thousands of production runs, the scrap rate for dual-process products with plating defects (missing plating) decreased from 11.01% to 0%, while also reducing the immersion time in the activation tank and the frequency of nickel tank dragging. Nickel tank dragging was a solution to the frequent plating defects before the improvement. To further reduce scrap due to missing plating defects, a whole copper plate is deposited in the nickel tank during the production of this type of board, thereby increasing the activity of the nickel tank and reducing plating defects. Conventional production boards only have localized areas of PADs immersing in nickel gold, with most areas covered by ink and CVL, resulting in a small plating area and a loading rate of only 0.2-0.3 dm² / L, leading to a slow reaction in the nickel tank solution. The principle of nickel tank dragging is to increase the plating area of ​​the board by dragging the tank, increasing the nickel tank loading rate to 0.8-1 dm² / L to catalyze the activity of nickel ions in the nickel tank. Under the improved method of this invention, plating defects no longer occur, thus reducing the frequency of nickel tank dragging, and even eliminating the nickel tank dragging process altogether.

[0016] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A method for improving plating defects in dual-surface treatment, characterized in that, All PADs to be electroplated with gold are electrically connected to a common point, and then electrically connected to the large copper layer of the production board through the common point. After the electroplating process is completed, all electrical connections at the common point are destroyed, and then immersion nickel-gold or nickel-palladium-gold treatment is performed.

2. The method for improving plating defects in dual-surface treatment according to claim 1, characterized in that, One way to break a common point is to use a CCD punching method to break the wire.

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