Nickel-palladium-gold lead frame and preparation method thereof

Abstract

According to the nickel-palladium-gold lead frame and the preparation method thereof provided by the invention, in the preparation method, acid pickling is carried out on the substrate after the nickel layer is plated and before the palladium layer is plated, the content of sulfuric acid in the acid pickling liquid per liter is 5.5%-8.0%, the acid liquid with high concentration can better clean organic matters, and the nickel passivation layer can be better and completely removed, so that the service life of the nickel-palladium-gold lead frame is prolonged, and the service life of the nickel-palladium-gold lead frame is prolonged. Therefore, the binding force of the nickel plating layer and the palladium plating layer is improved, the situation that the binding force of the nickel plating layer and the palladium plating layer is reduced due to the fact that the nickel plating layer is polluted by organic matter is avoided, the compactness of the nickel plating layer is improved, and the weldability of the nickel plating layer is improved; in the step S2, the step S23 is further included, the concentration of a gold cylinder is 0.8-1.6 g / L when the gold layer is plated, the intense reaction between gold plating liquid medicine and the nickel plating layer can be avoided, deep corrosion to the nickel plating layer is avoided, grain boundary corrosion is avoided, and the black disc phenomenon is avoided, so that the quality of the nickel plating layer is improved, and the defective product rate of the lead frame is reduced; and the defective product rate of the nickel-palladium-gold lead frame prepared according to the method is relatively low.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and in particular to a nickel-palladium-gold lead frame and a preparation method thereof. Background Art

[0002] The lead frame is the carrier of the integrated circuit chip, which is used to electrically connect the internal circuit lead ends of the chip with the external leads, and it acts as a bridge to connect with external wires.

[0003] When making a lead frame, it is necessary to electroplate a nickel-palladium-gold layer on a copper strip substrate; however, in the lead frame manufactured by the electroplating process of the lead frame in the prior art, during welding, an abnormal phenomenon of separation and blackening of the nickel plating layer and the palladium plating layer after the lead frame section is found at the upper plate welding position, resulting in a high defective rate of the lead frame; a slight black disk phenomenon is found after stripping the gold plating layer, that is, due to the violent reaction between the gold plating solution and the nickel layer, the nickel layer is deeply corroded and intergranular corrosion is generated, resulting in poor surface defects on the lead frame, resulting in poor density and solderability of the nickel layer, unstable thrust, poor bonding between the nickel layer and the palladium layer, and easy separation, which in turn results in a low yield.

[0004] Therefore, the manufacturing process of the lead frame in the prior art has room for further improvement. Summary of the invention

[0005] In view of this, in order to solve the technical problem that the manufacturing process of the nickel-palladium-gold lead frame in the above-mentioned prior art easily leads to poor bonding between the nickel layer and the palladium layer, and easy separation, the present application provides a nickel-palladium-gold lead frame and a preparation method thereof, in which the bonding between the nickel-plated layer and the palladium layer of the lead frame is good, and the two are not easy to separate, thereby greatly improving the yield of the lead frame.

[0006] First aspect The present application provides a method for preparing a nickel-palladium-gold lead frame, the method comprising the following steps: S1, roughening the surface of the substrate; S2, sequentially plating a nickel layer, a palladium layer and a gold layer on the substrate to obtain an electroplated substrate; S3, welding the electroplated substrate and the PCB board to obtain a nickel-palladium-gold plated lead frame; Wherein, in step S2, step S22 is included: after plating the nickel layer and before plating the palladium layer, the substrate is pickled, and the sulfuric acid content in the pickling liquid is 5.5%-8.0% per liter; In step S2, step S23 is also included: when plating the gold layer, the concentration of the gold cylinder is 0.8-1.6 g / L.

[0007] Compared with the prior art, in the preparation method of the nickel-palladium-gold lead frame of the present application, in step S1, the surface of the substrate is roughened to increase the adhesion effect between the nickel plating layer and the substrate, so that the nickel plating layer will not easily separate from the substrate; wherein, in step S2, after the nickel layer is plated, the substrate is cleaned with an acid solution having a sulfuric acid content of 5.5%-8.0% per liter to clean the organic matter on the nickel-plated substrate, and the acid solution with a stronger concentration can better clean the organic matter and can better completely remove the nickel passivation layer. Thereby, the bonding force between the nickel coating and the palladium coating is improved, and organic matter is prevented from polluting the nickel coating and reducing the bonding force between the nickel coating and the palladium coating, thereby improving the compactness of the nickel coating and improving the solderability of the nickel coating; in combination with step S23, the gold cylinder concentration is adjusted to 0.8-1.6 g / L, and the sulfuric acid concentration in the acid solution is combined to avoid a violent reaction between the gold plating solution and the nickel coating, avoid deep corrosion of the nickel coating, avoid intergranular corrosion, and avoid the black disk phenomenon, thereby improving the quality of the nickel coating and reducing the defective rate of the lead frame.

[0008] Preferably, step S2 further includes step S21: when plating the nickel layer, the nickel plating current is 23-30A.

[0009] Preferably, in step S21, the nickel plating temperature is 60-70° C. and the nickel plating concentration is 93-110 g / L.

[0010] Preferably, in step S23, it further includes: when the gold layer is plated, the substrate transmission speed is 1.5M / min-4.0M / min.

[0011] Preferably, in step S23, the gold plating current is further comprised of 0.7-1.2A.

[0012] Preferably, after step S1 and before step S2, the method further includes: S11, chemically cleaning the roughened substrate.

[0013] Preferably, in step S2, the thickness of the nickel plating layer is 0.5-2.0 μm, the thickness of the palladium plating layer is 0.02-0.15 μm, and the thickness of the gold plating layer is 0.005-0.015 μm.

[0014] Preferably, in step S22, it specifically includes: cleaning the nickel cylinder at an interval of time T1, wherein the cleaning step includes adding electrolytic treatment and using carbon core circulation treatment for a time period of T2.

[0015] Preferably, T1 is one month in length; T2 is 12 hours.

[0016] The nickel-palladium-gold lead frame and the preparation method thereof of the present application have at least the following technical effects: 1. By increasing the concentration in the acid solution, the nickel passivation layer can be completely removed, thereby improving the bonding strength of nickel and palladium and the weldability of the nickel layer. At the same time, the gold cylinder concentration is controlled at 0.8-1.6g / L, thereby reducing the corrosion of the gold cylinder solution to the nickel plating layer and avoiding the black disk phenomenon on the gold plating layer. The gold cylinder concentration and the acid concentration work together to strengthen the welding strength of the nickel plating layer and improve the yield rate of the lead frame. 2. By controlling the nickel plating current at 23-30A and matching the nickel plating concentration, the quality of the nickel plating layer can be improved by reducing the deposition rate of chemical nickel plating and improving the crystallization of the nickel plating layer; 3. By chemically cleaning the roughened substrate, C and O on the substrate can be removed, the cleanliness of the substrate surface can be increased, and the residual C and O can be prevented from contaminating the nickel plating layer; 4. By cleaning the nickel cylinder every month and adding electrolytic treatment and carbon core circulation treatment, the impurities in the nickel cylinder solution can be completely electrolyzed, making the solution in the nickel cylinder contain fewer impurities and improving the quality of the nickel plating.

[0017] Second aspect The present application provides a nickel-palladium-gold lead frame, which is prepared by the preparation method of the nickel-palladium-gold lead frame provided by any embodiment of the first aspect. The lead frame of the present application is prepared by a better process, and its yield rate is relatively high. At the same time, the nickel plating layer and the palladium plating layer are not prone to separation and blackening abnormal phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a method for preparing a nickel-palladium-gold lead frame provided in one embodiment of the present application; Figure 2 is a schematic structural diagram of a nickel-palladium-gold lead frame provided in one embodiment of the present application; Figure 3 yes Figure 2 A partial enlarged schematic diagram of .

[0019] Reference numerals: 1. nickel-palladium-gold lead frame; 2. pin; 3. lead frame unit. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail, clearly and completely in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.

[0021] In the description of this application, if there is a description of first or second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0022] Those skilled in the art should understand that, in the disclosure of the present application, the orientation or positional relationship indicated by terms such as "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", and "outside" are based on the orientation or positional relationship shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present application.

[0023] The present application is further described in detail below in conjunction with the accompanying drawings. Figures 1 to 3 illustrate.

[0024] First aspect The present application provides a method for preparing a nickel-palladium-gold lead frame, which is used to manufacture a nickel-palladium-gold lead frame, wherein the preparation method comprises the following steps: S1, roughening the surface of the substrate; S2, sequentially plating a nickel layer, a palladium layer and a gold layer on the substrate to obtain an electroplated substrate; S3, welding the electroplated substrate and the PCB board to obtain a nickel-palladium-gold plated lead frame; Wherein, in step S2, step S22 is included: after plating the nickel layer and before plating the palladium layer, the substrate is pickled, and the sulfuric acid content in the pickling liquid is 5.5%-8.0% per liter; In step S2, step S23 is also included: when plating the gold layer, the concentration of the gold cylinder is 0.8-1.6 g / L.

[0025] In the present application, the substrate material is preferably copper or copper alloy. First, the surface of the substrate is roughened so that the surface of the substrate has inverted mushroom-shaped particles, thereby improving the adhesion of the copper plate surface; when nickel is plated on the substrate, the substrate and the nickel plating layer are better bonded, reducing the probability of separation of the nickel plating layer from the substrate; at the same time, pickling is performed after the nickel plating layer, wherein the sulfuric acid content per liter in the pickling solution can ensure that the organic matter on the substrate after nickel plating is cleaned, and the acid solution with a stronger concentration can better clean the organic matter and can better passivate the nickel. The layer is completely and thoroughly removed, thereby improving the bonding strength of the nickel plating layer and the palladium plating layer, and avoiding organic matter contamination of the nickel plating layer and reducing the bonding strength of the nickel plating layer and the palladium plating layer, improving the compactness of the nickel plating layer, and thus improving the solderability of the nickel plating layer; in combination with step S23, the gold cylinder concentration is adjusted to 0.8-1.6g / L, and the sulfuric acid concentration in the acid solution can be combined to avoid a violent reaction between the gold plating solution and the nickel plating layer, avoid deep corrosion of the nickel plating layer, avoid intergranular corrosion, and avoid the black disk phenomenon, thereby improving the quality of the nickel plating layer and reducing the defective rate of the lead frame.

[0026] In this application, the test results of the acid concentration and gold cylinder concentration on the defective rate of nickel-palladium-gold lead frame are compared as follows: Serial number Acid concentration Gold cylinder concentration Bad ratio Example 1 6.0% 1.2g / L 2 / 42 Example 2 6.0% 1.4g / L 2 / 42 Example 3 7.0% 1.4g / L 1 / 42 Example 4 7.0% 1.5g / L 3 / 42 Example 5 8.0% 1.4g / L 1 / 42 Example 6 8.0% 1.5g / L 2 / 42 Referring to the comparative data of Examples 1 to 6 in the above table, it can be seen that when the acid concentration is relatively high and the gold cylinder concentration is relatively low, the probability of reducing the defective ratio increases.

[0027] Among them, in step S1, when roughening the substrate, any one of physical roughening, chemical roughening or electroplating methods can be used for roughening, and it is necessary to ensure that Ra after roughening is between 0.2-0.9 and Rz is between 2.0-9.1; wherein Ra is the unit of roughness, single-line scanning; Rz is the unit area, multi-line scanning.

[0028] Furthermore, in order to improve the optical cleanliness of the substrate surface, C and O on the substrate surface are removed to avoid residual C and O from contaminating the nickel plating layer. Therefore, after step S1 and before step S2, step S11 is also included: chemically cleaning the roughened substrate to avoid contaminating the nickel plating layer.

[0029] Further, in step S2, step S21 is also included: when the nickel layer is plated, the nickel plating current is 23-30A. In this step, the nickel plating current is set at 23-30A, so as to reduce the deposition rate of chemical nickel plating and improve the crystallization of the nickel plating layer to improve the quality of the nickel plating layer. In this application, the nickel plating current is preferably 25A.

[0030] Meanwhile, in step S21, it also specifically includes: the nickel plating temperature is 60-70°C; the nickel plating concentration is 93-110g / L; the nickel plating temperature is coordinated with the nickel plating concentration and the nickel plating current to further reduce the deposition rate of chemical nickel plating and improve the crystallization of the nickel plating layer to improve the quality of the nickel plating layer. In the present application, the nickel plating current is preferably 65°C, and the nickel plating concentration is preferably 100g / L.

[0031] Furthermore, in step S23, it specifically includes: when the gold layer is plated, the substrate transmission speed is 1.5M / min-4.0M / min; at the same time, in step S23, it specifically includes: the gold plating current is 0.7-1.2A; by controlling the substrate transmission speed, the transmission speed of the substrate in the gold cylinder is matched with the gold plating current and the gold cylinder concentration to ensure the effectiveness of the gold plating layer, to ensure that the gold cylinder solution will not over-react with the nickel plating layer, and will not produce defects on the nickel plating layer during gold plating, to avoid corrosion of the nickel plating layer, and to ensure the quality of the gold plating layer. In this embodiment, the substrate transmission speed is preferably 2M / min, and the gold plating current is preferably 1.0A.

[0032] Furthermore, in step S2, when plating the palladium layer, the palladium plating current is 2.5-3.8A, the palladium plating temperature is 50-60°C, and the palladium plating concentration is 2.8-4.4g / L. In this embodiment, the palladium plating current is preferably 3.2A, the palladium plating current is preferably 57°C, and the palladium plating concentration is preferably 3.9g / L.

[0033] It should be noted that in step S2 of the present application, the thickness of the nickel plating layer is 0.5-2.0 μm, the thickness of the palladium plating layer is 0.02-0.15 μm, and the thickness of the gold plating layer is 0.005-0.015 μm, wherein the thickness of the nickel plating layer, the palladium plating layer, and the gold plating layer are set in such a way that the nickel-palladium-gold lead frame has good bonding ability in the subsequent welding process, and the thickness of the electroplating layer can be controlled to reduce costs. In this embodiment, the thickness of the nickel plating layer is an intermediate value of 0.5-2.0 μm, the thickness of the palladium plating layer is an intermediate value of 0.02-0.15 μm, and the thickness of the gold plating layer is an intermediate value of 0.005-0.015 μm.

[0034] Furthermore, in step S22, it specifically includes: cleaning the nickel cylinder at an interval of T1 time, wherein the cleaning step includes increasing electrolytic treatment and using carbon core circulation treatment for T2 time; by increasing electrolytic treatment and carbon core circulation treatment, the impurities in the nickel cylinder solution can be completely electrolyzed, so that the solution in the nickel cylinder contains fewer impurities, thereby improving the quality of the nickel plating.

[0035] Among them, T1 is one month and T2 is 12 hours. Of course, T1 can also be less than one month, and T2 can be greater than 12 hours, so as to improve the cleaning degree of the nickel cylinder and ensure the nickel plating effect.

[0036] Second aspect The present application provides a nickel-palladium-gold lead frame, which is prepared by the method for preparing the nickel-palladium-gold lead frame provided in the first aspect above. Figure 2 , Figure 3 As shown, the nickel-palladium-gold lead frame 1 includes a plurality of lead frame units 3 arranged in an array and non-functional areas connected between adjacent lead frame units 3, all exposed areas on the upper and lower surfaces of the lead frame units 3 are provided with a nickel-palladium-gold plated layer, and the side walls and non-functional areas of the lead frame units 3 do not include a nickel-palladium-gold plated layer; wherein each lead frame includes a pin 2, and the pin 2 is used to connect to an external wire.

[0037] Among them, the lead frame of the present application is manufactured by adopting a better process, and its yield rate is relatively high. At the same time, the nickel plating layer and the palladium plating layer are not prone to the abnormal phenomenon of separation and blackening.

[0038] It should be noted that the various embodiments of the present application can be arbitrarily combined into a new embodiment if the solutions do not conflict and the technical solutions can coexist.

[0039] The present application is described in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the present application and its core ideas. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a nickel-palladium-gold lead frame, characterized in that: The method comprises the following steps: S1, roughening the surface of the substrate; S2, sequentially plating a nickel layer, a palladium layer and a gold layer on the substrate to obtain an electroplated substrate; S3, welding the electroplated substrate and the PCB board to obtain a nickel-palladium-gold plated lead frame; Wherein, in step S2, step S22 is included: after plating the nickel layer and before plating the palladium layer, the substrate is pickled, and the sulfuric acid content in the pickling liquid is 5.5%-8.0% per liter; In step S2, step S23 is also included: when plating the gold layer, the concentration of the gold cylinder is 0.8-1.6 g / L.

2. The method for preparing a nickel-palladium-gold lead frame according to claim 1, characterized in that: In step S2, step S21 is also included: when plating the nickel layer, the nickel plating current is 23-30A.

3. The method for preparing a nickel-palladium-gold lead frame according to claim 2, characterized in that: In step S21, specifically, the nickel plating temperature is 60-70°C; and the nickel plating concentration is 93-110 g / L.

4. The method for preparing a nickel-palladium-gold lead frame according to claim 1, characterized in that: In step S23, specifically, it also includes: when the gold layer is plated, the substrate transmission speed is 1.5M / min-4.0M / min.

5. The method for preparing a nickel-palladium-gold lead frame according to claim 4, characterized in that: In step S23, the gold plating current is specifically also included: 0.7-1.2A.

6. The method for preparing a nickel-palladium-gold lead frame according to claim 1, characterized in that: After step S1 and before step S2, the method further includes: S11, chemically cleaning the roughened substrate.

7. The method for preparing a nickel-palladium-gold lead frame according to claim 1, characterized in that: In step S2, the thickness of the nickel plating layer is 0.5-2.0 μm, the thickness of the palladium plating layer is 0.02-0.15 μm, and the thickness of the gold plating layer is 0.005-0.015 μm.

8. The method for preparing a nickel-palladium-gold lead frame according to any one of claims 1 to 7, characterized in that: In step S22, it specifically includes: cleaning the nickel cylinder at an interval of time T1, wherein the cleaning step includes adding electrolytic treatment and using carbon core circulation treatment for a time period of T2.

9. The method for preparing a nickel-palladium-gold lead frame according to claim 8, characterized in that: T1 is one month long; T2 is 12 hours.

10. A nickel-palladium-gold lead frame, characterized in that: The lead frame is prepared by the method for preparing the nickel-palladium-gold lead frame as described in any one of claims 1 to 9.

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