Plating materials and electronic parts

Abstract

To provide a plating material and an electronic component that have excellent solder wettability and resin adhesion.SOLUTION: A plating material forming a resin on a surface or sealing a surface with a resin has a conductive substrate, a roughened plating layer arranged on the conductive substrate, and a noble metal plating layer arranged on the roughened plating layer. If an area indicated by a hue larger than 30% of the maximum detection intensity of the outermost surface layer component of the noble metal plating layer when mapping analysis is conducted by EPMA with an observation magnification of 50000x from the side of the noble metal plating layer is defined as a coated area with the outermost surface layer component, the coverage of the outermost surface layer component for the surface of the plating material is at least 70% of the observation visual field area.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plating material and an electronic component. [Background technology]

[0002] In recent years, there has been an increasing demand for improved adhesion between composites of metal materials and resins. In particular, for automotive applications, there is a demand for even better adhesion due to the increasing electronics required around the engine bay, which is subject to harsh conditions.

[0003] Against this background, techniques have been proposed for roughening the plated surface of a lead frame in order to improve adhesion between the lead frame and mold resin in a resin-encapsulated semiconductor device (Patent Documents 1, 2, and 3).

[0004] By applying these conventional techniques, resin adhesion has been improved in high temperature and high humidity tests such as JEDEC-LEVEL1. However, in the area where a semiconductor chip is mounted, where the chip needs to be joined by soldering or die bonding, it is known that the roughening plating inhibits solder wettability. Therefore, for example, Patent Document 4 proposes a configuration in which areas that require soldering such as outer lead parts are not roughened.

[0005] Furthermore, as a method for improving solder wettability, Patent Document 5 discloses a technique for forming a palladium plating or a gold plating on the surface of a roughened plating. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-29439 [Patent Document 2] Japanese Patent Application Publication No. 10-27873 [Patent Document 3] JP 2006-93559 A [Patent Document 4] JP 2008-103455 A [Patent Document 5] Japanese Patent Application Publication No. 4-115558 Summary of the Invention [Problem to be solved by the invention]

[0007] In particular, in the chip mounting areas of electronic components, there is an increasing need to reduce flux residue in order to prevent contamination of the chips, and studies are being conducted on mounting with low-residue flux or flux-free mounting. One method for improving this is to coat the surface of a conductive base material with precious metal plating such as palladium plating or gold plating.

[0008] However, the thickness of the precious metal plating tends to be thin. Therefore, when a roughened plating layer is provided on a conductive substrate, if a thin precious metal plating is applied on the roughened plating layer, current concentrates on the convex parts of the roughened plating, no precious metal plating is formed in the concave parts, and the roughened plating layer is exposed. The present inventors have found that the oxidation of the exposed parts of the roughened plating layer in this way deteriorates the solder wettability. In addition, it has been found that the solder wettability of a plated material using a solder containing low residue flux is particularly deteriorated in the above-mentioned situation.

[0009] As a means for solving these problems, it is conceivable to not perform roughening treatment on the areas where solder bonding is required, in other words, to perform roughening treatment only on the parts of the metal material that are covered with resin, as in the technology disclosed in the above-mentioned Patent Document 4. However, localized roughening treatment reduces the roughness, making it difficult to ensure resin adhesion.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a plating material and an electronic component having good solder wettability and resin adhesion. [Means for solving the problem]

[0011] As a result of intensive research, the inventors have found that the above-mentioned problems can be solved by forming a roughened plating layer and a precious metal plating layer on a conductive base material and controlling a predetermined coverage rate of the precious metal plating layer with respect to the surface of a plating material.

[0012] One aspect of an embodiment of the present invention completed based on the above findings is a plating material in which a resin is molded onto a surface or the surface is sealed with a resin, the plating material having a conductive base material, a roughened plating layer provided on the conductive base material, and a precious metal plating layer provided on the roughened plating layer, in which, when a mapping analysis is performed using an EPMA at an observation magnification of 50,000 times from the precious metal plating layer side, a location that is shown with a color tone that is 30% or more of the maximum detection intensity of the outermost layer component of the precious metal plating layer is defined as a location covered by the outermost layer component, and the coverage of the outermost layer component with respect to the surface of the plating material is 70% or more of the observation field area.

[0013] In one embodiment of the plating material of the present invention, the arithmetic mean roughness Sa measured from the noble metal plating layer side is 0.1 to 0.3 μm.

[0014] In another embodiment of the plating material of the present invention, the precious metal plating layer has an average thickness of 0.006 to 0.1 μm.

[0015] In yet another embodiment of the plating material of the present invention, the noble metal plating layer is made of palladium plating and gold plating.

[0016] In yet another embodiment of the plating material of the present invention, the precious metal plating layer comprises a palladium plating layer having an average thickness of 0.005 to 0.05 μm provided on the roughened plating layer, and a gold plating layer having an average thickness of 0.001 to 0.05 μm provided on the palladium plating layer.

[0017] In yet another embodiment of the plating material of the present invention, a thiol compound is contained on the surface of the noble metal plating layer.

[0018] Another aspect of the present invention is an electronic component including a plating material according to an embodiment of the present invention. Effect of the Invention

[0019] According to the embodiments of the present invention, it is possible to provide a plating material and an electronic component having good solder wettability and resin adhesion. [Brief description of the drawings]

[0020] [Figure 1] 1A is a schematic cross-sectional view of a plating material according to an embodiment of the present invention, and FIG. 1B is an enlarged schematic view of a portion enclosed by a dotted line frame shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the plating material and electronic components of the present invention will be described, but the present invention should not be construed as being limited thereto, and various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention.

[0022] <Plating material composition> Fig. 1(A) shows a schematic cross-sectional view of a plating material according to an embodiment of the present invention. Fig. 1(B) shows an enlarged schematic view of the area surrounded by the dotted line frame shown in Fig. 1(A). The plating material according to an embodiment of the present invention is a plating material in which a resin is molded on a surface or a surface is sealed with a resin, and has a conductive base material, a roughened plating layer provided on the conductive base material, and a precious metal plating layer provided on the roughened plating layer.

[0023] (Conductive base material) The conductive substrate is not particularly limited, but for example, copper, copper alloy, iron, iron alloy, stainless steel, 42 alloy, etc. are preferably used, among which, from the viewpoint of conductivity and strength, copper and copper alloy are preferred, and phosphor bronze, brass, Corson copper, oxygen-free copper, tough pitch copper, etc. are more preferred. Specific examples of copper alloys that can be used as the conductive substrate include C11000, C10200, C19400, C70250, C26000, and C52100, as specified by the Copper Development Association (CDA). In addition, a resin layer may be compounded with a metal substrate. An example of a resin layer compounded with a metal substrate is an electrode portion on an FPC or FFC substrate.

[0024] (roughened plating layer) The roughened plating layer exerts its effect when provided at a location that is in close contact with the resin, and the anchor effect allows the conductive substrate and the resin to maintain a state of adhesion for a long period of time. The roughened plating layer may be provided not only at a location that is in close contact with the resin, but also at a location where good solderability is required. In the prior art, it is considered that roughened plating is not suitable for locations where solderability is required because of poor wettability, but the present invention improves this point and provides a plating material that does not inhibit solder wettability.

[0025] The type of the roughened plating layer is preferably nickel, nickel alloy, copper, or copper alloy, and particularly preferably nickel or nickel alloy, because it is effective as a base layer for the precious metal plating layer. The average thickness of the roughened plating layer is not particularly limited, but is preferably formed to, for example, 0.2 to 2 μm. If the average thickness of the roughened plating layer is less than 0.2 μm, the resin adhesion is low and long-term reliability is poor, while if it exceeds 2 μm, the productivity and the ratio of precious metal plating coverage described below tend to be low. In addition, from the viewpoint of productivity and effect, the average thickness of the roughened plating layer is more preferably 0.3 to 1.5 μm, and even more preferably 0.5 to 1 μm.

[0026] (Precious metal plating layer) The precious metal plating layer is a layer formed mainly to improve solder wettability, and is formed of, for example, palladium, palladium alloy, gold, or gold alloy. In particular, from the viewpoint of heat resistance and solder wettability, it is preferable to configure the layer in the order of palladium plating and gold plating from the roughened plating layer side. The average thickness of the precious metal plating layer is not particularly limited, but it is preferable to form it thin from the viewpoint of cost, productivity, and further improvement effect of solder wettability, and it can be formed to be 0.006 to 0.1 μm. In particular, from the viewpoint of heat resistance and precious metal saving, the precious metal plating layer is preferably composed of a palladium plating layer with an average thickness of 0.005 to 0.05 μm provided on the roughened plating layer, and a gold plating layer with an average thickness of 0.001 to 0.05 μm provided on the palladium plating layer. In addition, the average thickness of the palladium plating layer is more preferably 0.01 to 0.03 μm, and even more preferably 0.015 to 0.02 μm. The average thickness of the gold plating layer is more preferably 0.003 to 0.03 μm, and even more preferably 0.005 to 0.02 μm.

[0027] In the plating material according to the embodiment of the present invention, when a mapping analysis is performed from the precious metal plating layer side by an EPMA (Electron Probe Micro Analyzer) at a magnification of 50,000 times, the coverage of the outermost layer component on the surface of the plating material is 70% or more of the observation field area, when the area shown by a color tone of 30% or more of the maximum detection intensity of the outermost layer component of the precious metal plating layer is defined as the covered area by the outermost layer component. According to this configuration, the exposure of the roughened plating layer is suppressed, and good solder wettability can be obtained while ensuring resin adhesion. In addition, even if mounting is performed with solder with little flux residue or flux-free solder, a plating material with good solder wettability and resin adhesion can be obtained. In the plating material according to the embodiment of the present invention, the coverage of the outermost layer component is preferably 75% or more of the observation field area, and more preferably 80% or more.

[0028] The above-mentioned "coverage rate of the outermost layer component on the surface of the plating material" indicates the coverage rate of the one component on the surface of the plating material when the precious metal plating layer is formed of one component (e.g., palladium or gold). On the other hand, when the precious metal plating layer has a palladium plating layer on the bottom and a gold plating layer on the top, the outermost layer component is gold, so the coverage rate of the gold on the surface of the plating material indicates the coverage rate.

[0029] As an example of a method for measuring the coverage of the outermost layer component on the surface of the above-mentioned plated material, first, the precious metal plating layer side of the plated material is observed at a magnification of 50,000 times by EPMA. Note that, as a result of intensive research by the present inventors, if the magnification is less than 50,000 times, the detection intensity in the roughened recesses cannot be sufficiently detected, and if the magnification exceeds 50,000 times, the roughened unevenness becomes an index of local enlargement, so the observation magnification is set. Next, the precious metal components in the outermost layer are mapped, and the parts that are shown in a color tone of 30% or more of the maximum detection intensity are extracted as "covered parts", and the area ratio is calculated and defined as the above-mentioned "coverage". If the coverage is low, the uncovered parts are oxidized when exposed to the atmosphere, which results in the inhibition of solder wettability. In addition, the above-mentioned coverage is measured by selecting any three points on the surface of the precious metal plating layer side of the plated material, and calculating the average value.

[0030] The plating material according to the embodiment of the present invention preferably has an arithmetic mean roughness Sa of 0.1 to 0.3 μm measured from the precious metal plating layer side. When the arithmetic mean roughness Sa measured from the precious metal plating layer side is 0.1 μm or more, the anchor effect is enhanced and the adhesion to the resin is improved, and when it is 0.3 μm or less, the coverage rate of the precious metal plating on the recesses (valleys) of the roughened surface is improved, and as a result, the solder wettability can be improved. In addition, when the arithmetic mean roughness Sa is 0.2 μm or less, damage to the tip portion can be suppressed. The plating material according to the embodiment of the present invention more preferably has an arithmetic mean roughness Sa measured from the precious metal plating layer side of 0.15 to 0.18 μm, and even more preferably 0.16 to 0.17 μm.

[0031] <Method of manufacturing plating materials> In the method for producing a plated material according to an embodiment of the present invention, a roughened plating layer is first formed on a conductive base material, and then a precious metal plating layer is formed on the conductive base material by wet (electrical or electroless) plating.

[0032] The roughening plating conditions for forming the roughened plating layer are shown below. - Solution composition: Desired plating solution composition containing nickel, nickel alloy, copper, copper alloy, etc. Plating temperature: 40~60℃ ·Current density: 5~15A / dm 2

[0033] The precious metal plating conditions for forming the precious metal plating layer are shown below. - Solution composition: Desired plating solution composition containing palladium, gold, etc. Plating temperature: 40~60℃ ·Current density: 0.05~2A / dm 2 Stirring speed: 800~1200rpm Ultrasonic mixing: 28kHz, 200~600W Although ultrasonic stirring is not necessary, it is preferable to carry it out.

[0034] As described above, by stirring the plating solution under the precious metal plating conditions of high stirring speed, low current density, and ultrasonic waves, electrodeposition of the roughened plating layer into the recesses is promoted, and the precious metal plating in the recesses can be formed very thin and uniformly, thereby improving the coverage of the precious metal plating layer.

[0035] (Sealing treatment) It is preferable to mount the product by soldering immediately after forming the precious metal plating layer, but if there is a possibility of long-term storage or exposure to poor surrounding environments, it is preferable to perform a sealing treatment. The sealing treatment can ensure long-term solder wettability and resin adhesion. It is particularly preferable to use a substance with a reducing effect as a component of the sealing treatment. For example, by using or implementing a sealing agent with a mercapto group, oxidation of the lightly covered roughened plated area can be prevented, and the reducing effect can greatly improve the solder wettability.

[0036] Depending on the type of sealing treatment and the coating thickness, there is a risk of reducing resin adhesion, so it is preferable to carry out the sealing treatment for 60 seconds or less, preferably 30 seconds or less, and to appropriately control the coating thickness.

[0037] Furthermore, by carrying out the sealing treatment, it is possible to significantly suppress the deterioration of solder wettability after, for example, a high temperature and high humidity test (85°C-85%-8 hours).

[0038] The sealing treatment of the plating material according to the embodiment of the present invention can be carried out using a known sealing agent and method. For example, the sealing treatment can involve forming a coating film containing a thiol compound.

[0039] <Applications of plating materials> The use of the plating material according to the embodiment of the present invention is not particularly limited, but it can be used as a material for electronic components that require good adhesion to resin, and in particular, it can be used as a material for electronic components that undergo resin molding, resin sealing, molding, etc., in which the surface is solidified with resin to protect against factors such as impact, temperature, and humidity. Examples of such electronic components include metal electronic components such as lead frames and bus bar modules. The plating material according to the embodiment of the present invention has very good adhesion between the surface of the conductive material and the resin, even when used as a material for electronic components used in harsh environments such as around the engine room for in-vehicle use, for example. EXAMPLES

[0040] Examples of the present invention and comparative examples are presented below, but these are provided for a better understanding of the present invention and are not intended to limit the present invention.

[0041] <Test Example 1> (Preparation of conductive substrate) In Examples 1 to 7 and Comparative Example 1, a conductive substrate (C11000: 99.9% Cu) was subjected to cathodic electrolytic degreasing in an alkaline degreasing bath containing 50 g / L of sodium hydroxide at 5 A / dm 2 After that, the sample was pickled in a pickling solution of 10% sulfuric acid and 50 g / L ammonium fluoride for 30 seconds.

[0042] (roughening plating treatment) Next, a roughening plating process was performed by adjusting the composition of the plating bath, the temperature of the plating solution, the current density, and the plating time by electroplating, and a roughening plating layer was formed on the surface of the conductive substrate. The roughening plating bath components in Examples 1 to 7 and Comparative Example 1 were all the same, with a Ni metal content of 130 g / L, boric acid of 25 g / L, and a pH of 3.3. Here, the Ni metal content was composed of nickel sulfamate tetrahydrate and Ni chloride as Ni salts. More specifically, nickel sulfamate tetrahydrate: Ni(NH2SO3)2·4H2O=294 g / L (about 300 g / L), Ni amount of 53.5 g / L, nickel chloride hexahydrate: NiCl2·6H2O=about 310 g / L, Ni amount of 76.5 g / L. The temperature of the plating solution in Examples 1 to 7 and Comparative Example 1 was 45° C., and the current density was 10 A / dm 2 It was decided.

[0043] (Palladium plating) Next, a palladium plating process was performed by adjusting the composition of the plating bath, the temperature of the plating solution, the current density, the stirring speed, the use of ultrasonic stirring, and the plating time in electroplating, to form a palladium plating layer on the surface of the roughened plating layer. The plating bath components in Examples 1 to 7 and Comparative Example 1 were all the same, and were Parabright SST-L (product name, manufactured by Japan High Purity Chemical Co., Ltd.). The palladium plating conditions are shown in Table 1. The ultrasonic stirring conditions were 28 kHz and 200 W.

[0044] [Table 1]

[0045] (Gold plating) Next, gold plating was performed by adjusting the composition of the plating bath, the temperature of the plating solution, the current density, the stirring speed, the use of ultrasonic stirring, and the plating time in electroplating to form a gold plating layer on the surface of the palladium plating layer. The plating bath components in Examples 1 to 7 and Comparative Example 1 were all the same, and were Afterplate (product name, manufactured by Japan High Purity Chemical Co., Ltd.). The gold plating conditions are shown in Table 2. The ultrasonic stirring conditions were 28 kHz and 200 W.

[0046] [Table 2]

[0047] (evaluation) -Average plating thickness The average thickness of each plating was confirmed by calculating the average value at any five points using a fluorescent X-ray thickness gauge (Hitachi High-Tech SFT9500) with a collimator diameter of 0.2 mm and a thickness measurement time of 30 seconds.

[0048] - Coverage rate of the outermost layer component on the surface of the plating material The coverage of the outermost layer component on the surface of the plated material was measured. Specifically, the plated material was observed from the precious metal plating layer side by EPMA at a magnification of 50,000 times. Next, the precious metal component (Au component in Examples 1 to 7 and Comparative Example 1) in the outermost layer was mapped, and the portion shown in a color tone of 30% or more of the maximum detection intensity was extracted as a "covered portion", and the area ratio was calculated and defined as the "coverage rate". In addition, the coverage rate was measured by selecting three arbitrary points on the surface of the precious metal plating layer side of the plated material and measuring the average value. The measurement conditions for the EPMA are as follows. Scan Type: Beam Scan Acceleration voltage: 15.0 kV ·Irradiation current: 5.390e -8 A Measurement time: 25.00 ms Number of measurement points: 256 x 256

[0049] Arithmetic mean roughness Sa The arithmetic mean roughness Sa of the plated material was measured from the precious metal plating layer side. Specifically, a Keyence laser microscope (VK-X150) was used, with an observation magnification of 1000 times, a spot diameter of φ0.8 mm, and a measurement area of ​​100 μm × 100 μm. The average value of five measurements (N5) was calculated and used as the Sa value of the surface of the plated material test piece.

[0050] Share Strength The surface of the plated material test piece was molded with resin to form a sample, and the shear strength was measured in a pudding cup mold test. The test conditions were: Resin: Hitachi Chemical Co., Ltd. GE-7470LA resin; Area of ​​the pudding cup bottom: 10 mm 2 The resin molding time was 120 seconds, and the mold cure time was 8 hours at 175°C. The average value of 10 shear force measurements (N10) was calculated and used as the shear strength. The shear was measured with a Daisy Bond Tester (Series 4000) at a shear speed of 100 μm / sec.

[0051] Solder wetted area After cutting the test piece to a size of 10 mm x 50 mm, it was immersed in Sn-3.0Ag-0.5Cu solder at a bath temperature of 245°C for 10 seconds at a immersion speed of 10 mm / sec. 2 The percentage of the wet area was calculated assuming that the wet area was 100%.

[0052] Table 3 shows the test conditions and test results for the above-mentioned Examples 1 to 7 and Comparative Example 1.

[0053] [Table 3]

[0054] (Evaluation Results) As shown in Table 3, it is understood that Examples 1 to 7 can provide a roughened plated material that has excellent solder wettability while maintaining shear strength. In particular, it is understood that even when the roughened plated thickness is thick and the roughness is high, good solder wettability is exhibited, and excellent solder wettability is maintained compared to Comparative Example 1. This is because the above-mentioned standardized coverage rate is 70% or more, and thus exposure of the roughened plated layer is suppressed, thereby obtaining good solder wettability while ensuring resin adhesion. The coverage of the outermost layer component in Examples 2 and 4 to 7 is described as "70 or more" and "84 or more", respectively, but these are estimated values ​​and not actual measured values. The coverage of the outermost layer component in Example 2 is the coverage of the outermost layer component estimated by back-calculating from the solder wetted area in Example 2, assuming that the relationship between the coverage of the outermost layer component and the solder wetted area in Example 1 and Comparative Example 1 is linear. In addition, the coverage of the outermost layer component in Examples 4 to 7 is highly likely to be higher than the coverage of the outermost layer component in Example 1, when Example 1 is used as a reference, because the Au plating thickness increase, the Pd plating thickness increase (thereby reducing the surface roughness of the roughening plating), strong stirring, and ultrasonic waves are performed. In addition, the shear strength of Example 5 was not measured.

[0055] <Test Example 2> In Examples 8 to 11, the sealing agent was applied by immersion or electrolysis to the surface of the plated material produced in Example 1, and then dried with hot air. Table 4 shows the sealing treatment conditions.

[0056] [Table 4]

[0057] For each of the plating materials of Examples 8 to 11, the shear strength was measured in the same manner as in Example 1. In addition, each plating material was left in a high-temperature and high-humidity environment of 85°C and 85RT% for 8 hours, and then the solder wetted area was evaluated in the same manner as in Test Example 1. The evaluation results are shown in Table 5.

[0058] [Table 5]

[0059] (Evaluation Results) As shown in Table 5, there is a significant difference in the solder wettability after the high temperature and high humidity test depending on whether or not the sealing treatment is performed. In Example 1, the solder wettability is ensured compared to Comparative Example 1, but it tends to be lower. On the other hand, in Examples 8 to 11 in which the sealing treatment is performed, the solder wettability is sufficiently ensured even after the environmental test, and this makes it possible to provide a plating material with excellent long-term reliability.

Claims

1. A plating material that has a resin molded on its surface or a resin sealed on its surface, A conductive substrate; A roughened plating layer provided on the conductive base material; a precious metal plating layer provided on the roughened plating layer; A plating material having a coverage rate of the outermost layer component to the surface of the plating material is 70% or more of an observation field area, when a mapping analysis is performed from the precious metal plating layer side by EPMA at an observation magnification of 50,000 times and a portion shown with a color tone of 30% or more of a maximum detection intensity of the outermost layer component of the precious metal plating layer is defined as a portion covered by the outermost layer component, The precious metal plating layer is A palladium plating layer having an average thickness of 0.005 to 0.05 μm provided on the roughened plating layer; and A gold plating layer having an average thickness of 0.001 to 0.05 μm provided on the palladium plating layer. It consists of: the plating material is an electroplating material; The plating material has an arithmetic mean roughness Sa of 0.1 to 0.3 μm as measured from the precious metal plating layer side.

2. 2. The plated material according to claim 1, wherein the precious metal plating layer has an average thickness of 0.006 to 0.1 μm.

3. The plating material according to claim 1 or 2, further comprising a thiol compound on a surface of the noble metal plating layer.

4. An electronic component comprising the plating material according to any one of claims 1 to 3.

Images