Metal surface roughening method

Abstract

The invention discloses a metal surface coarsening method, which belongs to the technical field of metal surface coarsening, and comprises the following steps: preparing a metal material to be coarsened; roughening the metal on the surface of the metal in a mode of electroplating multiple layers of metal; the method for electroplating the multi-layer metal comprises the following steps: electroplating by using pulse square waves with positive and negative currents and adjusting the magnitude of the positive current, the positive current time, the magnitude of the negative current, the negative current time and the power-off time, according to the metal surface roughening method disclosed by the invention, the binding force of the lead frame subsequently packaged in a high-function region and packaging resin is remarkably improved, the product performance problem caused by insufficient binding force is effectively avoided, meanwhile, the problem that excessive glue in a non-function region is difficult to remove is avoided, and the product quality is improved by accurately controlling the roughening treatment range. The processing area of the lead frame is reduced, and the usage amount of coarsening liquid medicine is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface roughening, and in particular relates to a metal surface roughening method. Background Art

[0002] The wire bonding between the chip and the inner pins of the lead frame, as well as the performance of the pad portion, are crucial to the quality of the package. To this end, the inner pins of the pad portion and the ends of the lead frame are often electroplated with metal materials such as silver. At the same time, to improve the solderability of the substrate after the resin protective film is formed, specific areas of the outer leads are plated with tin-lead (Sn-Pb). However, the existing process requires a wet treatment process after molding the resin protective film. This process has many disadvantages, such as reduced reliability of the molded product, and the wet treatment involves a complex process, which increases production costs and time costs. It may also introduce impurities due to improper operation, affecting product quality. Summary of the Invention

[0003] In view of the above situation, in order to overcome the defects of the existing technology, the present invention aims to provide a new metal surface roughening method to replace the traditional wet treatment process, while improving product performance, reducing production costs and time costs, and improving product quality.

[0004] In order to achieve the above object, the following technical solution is adopted: The present invention provides a metal surface roughening method, comprising:

[0005] Preparing the metal material to be roughened;

[0006] Roughening the metal by electroplating multiple layers of metal on the metal surface;

[0007] Methods for electroplating multiple layers of metal include: using a pulsed square wave with positive and negative currents, and electroplating by adjusting the positive current size, positive current time, negative current size, negative current time and power-off time.

[0008] Furthermore, the positive current is 0.2 amp to 0.33 amp, the positive current time is 20000 μsec to 35000 μsec, the negative current is 0.0615 amp to 0.128 amp, the negative current time is 1800 μsec to 3200 μsec, and the power-off time is 600 μsec to 1200 μsec.

[0009] Furthermore, the multi-layer metal is a copper layer, a nickel layer, a target layer and a gold layer.

[0010] Furthermore, the metal material to be roughened includes a lead frame.

[0011] Furthermore, the lead frame gold substrate to be roughened includes alloy 42 alloy material.

[0012] The beneficial effects of the present invention are:

[0013] (1) The metal surface roughening method of the present invention significantly improves the bonding strength between the lead frame and the encapsulation resin in the high-functional area (which may be the metal area) during subsequent encapsulation, effectively avoiding product performance problems caused by insufficient bonding strength, and also avoiding the problem of glue overflow in the non-functional area being difficult to remove;

[0014] (2) By precisely controlling the range of the roughening treatment, the processing area of the lead frame is reduced, and the amount of roughening solution used is reduced;

[0015] (3) This method has the significant advantages of stable process, high yield and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a SEM image of a metal surface roughening method after roughening according to the present invention;

[0017] Figure 2 This is a current waveform diagram from Run 18 to Run 21 of a metal surface roughening method of the present invention;

[0018] Figure 3 This is a data table of copper electroplating test results of a metal surface roughening method of the present invention.

[0019] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0022] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the experimental materials used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0023] Example:

[0024] Reference Figure 1-3 , an embodiment of the present invention provides: a metal surface roughening method, comprising:

[0025] A lead frame with an alloy 42 alloy material as a gold base material was prepared as the metal material to be roughened.

[0026] The lead frame is made of Alloy 42 alloy, which has a thermal expansion coefficient similar to that of semiconductor chips, effectively reducing deformation caused by thermal stress during the packaging process. This material serves as the roughened material, providing a base for subsequent electroplating roughening. Furthermore, by precisely identifying high-function and non-functioning areas of the lead frame (where the high-function areas can be metal), subsequent roughening treatment is performed only on these areas, reducing the processing area and thus reducing roughening solution consumption, thereby improving packaging quality and reducing costs.

[0027] The copper layer, nickel layer, target layer and gold layer are electroplated in sequence on the high-functional area of the lead frame metal surface to achieve surface roughening through multi-layer metal deposition.

[0028] In high-function areas, a copper layer is electroplated first, using copper’s good conductivity and ductility to form a base layer and enhance the adhesion of subsequent metal layers;

[0029] Next, a nickel layer is plated to enhance surface hardness and corrosion resistance; a target layer is then plated to optimize specific properties; and finally, a gold layer is applied, whose high chemical stability protects the internal metal layers. These multiple metal layers form a rugged microstructure in highly functional areas, enhancing the bond between these areas and the encapsulation resin, ensuring a tight adhesion and preventing excess adhesive from overflowing in non-functional areas.

[0030] Use a pulsed square wave with positive and negative currents, control the positive current size between 0.2amp and 0.33amp, set the positive current time between 20000μsec and 35000μsec, adjust the negative current size between 0.0615amp and 0.128amp, maintain the negative current time between 1800μsec and 3200μsec, and maintain the power-off time between 600μsec and 1200μsec to electroplate the high-functional area.

[0031] Specifically: Combined Figures 2 to 3As shown, the experimental condition parameters are: A represents the positive current size, B represents the negative current size, C represents the positive current time, D represents the reverse current time, and E represents the power-off time. Experimental results: Grain size is the particle size. Run18 current waveform parameters are: positive current size: 0.33amp, positive current time: 20000μsec, negative current size: 0.0165amp, negative current time: 1800μsec, power-off time: 600μsec, and the corresponding average particle size is: 595nm. Run19 current waveform parameters are: positive current size: 0.33amp, positive current time: 35000μsec, negative current size: 0.054amp, negative current time: 2600μsec, power-off time: 800μsec, and the corresponding average particle size is: 607nm. The Run20 current waveform parameters are: positive current: 0.33 amp, positive current duration: 50,000 μsec, negative current: 0.091 amp, negative current duration: 3,200 μsec, and power-off duration: 1,200 μsec. The corresponding average particle size is 646 nm. The Run21 current waveform parameters are: positive current: 0.2 amp, positive current duration: 20,000 μsec, negative current: 0.128 amp, negative current duration: 1,800 μsec, and power-off duration: 600 μsec. The corresponding average particle size is 605 nm.

[0032] The particle sizes corresponding to the experimental conditions of Run18, Run19, Run20 and Run21 meet the metal surface roughness requirements well.

[0033] During the electroplating process, a positive current causes metal ions to deposit on the surface of high-functional areas, creating a roughened structure. A negative current dissolves excess or irregularly deposited metal, smoothing the surface. A power outage controls ion diffusion and the deposition rhythm. By precisely adjusting these parameters, the metal deposition and dissolution processes are controlled, ensuring uniform surface roughness in high-functional areas and significantly improving process stability. This reduces the processing area and reduces chemical consumption.

[0034] After testing, it was found that after being processed by the method of the present invention, the particle size enables the metal surface to achieve an ideal roughening effect, thereby realizing the beneficial effects of the present invention in improving the bonding strength between the lead frame and the packaging resin, reducing the processing area, and reducing costs.

[0035] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0036] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and actual applications are not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, any method and embodiment similar to the technical solution without creative design shall fall within the scope of protection of the present invention.

Claims

1. A method for roughening a metal surface, characterized in that: include: Preparing the metal material to be roughened; Roughening the metal by electroplating multiple layers of metal on the metal surface; Methods for electroplating multiple layers of metal include: using a pulsed square wave with positive and negative currents, and electroplating by adjusting the positive current size, positive current time, negative current size, negative current time and power-off time.

2. A metal surface roughening method according to claim 1, characterized in that: The magnitude of the positive current is 0.2 amp to 0.33 amp, the positive current time is 20000 μsec to 35000 μsec, the magnitude of the negative current is 0.0615 amp to 0.128 amp, the negative current time is 1800 μsec to 3200 μsec, and the power-off time is 600 μsec to 1200 μsec.

3. A metal surface roughening method according to claim 1, characterized in that: The multi-layer metal comprises a copper layer, a nickel layer, a target layer and a gold layer. 4 . The metal surface roughening method according to claim 1 , wherein the metal material to be roughened comprises a lead frame. 5 . The metal surface roughening method according to claim 4 , wherein the lead frame gold substrate to be roughened comprises an alloy 42 alloy material.

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