JP4027642B2 - Nickel-based surface treatment film with excellent heat-resistant adhesion to resin - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nickel-based surface treatment film formed on the surface of a metal substrate in order to provide extremely strong adhesive force when bonding a target substrate, particularly a metal substrate and a resin. More specifically, the present invention relates to a nickel-based surface treatment film that can maintain excellent adhesion even when the metal-resin bonded body is placed in a high temperature environment of 200 ° C. to 300 ° C.
[0002]
[Prior art]
Many electronic and electrical parts such as printed wiring boards, lead frames, LSIs, and the like use joints between metal and resin. In particular, in thermosetting resins such as epoxy resins and polyimide resins used in such fields or thermoplastic resins having a high molding temperature, it is necessary to expose the entire part to a high temperature of 200 ° C. to 300 ° C. when molding these resins. There is. In addition, in order to form a wiring pattern with a copper foil adhered on a resin, it is necessary to go through a harsh manufacturing process such as contact with a chemical such as an organic solvent, acid, and alkali. Furthermore, when mounting active components such as semiconductor elements and passive components such as LCR, soldering is used, but because of the recent environmental problems, lead solder cannot be used, so the solder reflow temperature will become even higher. It's getting on.
[0003]
In such a situation, if the adhesion between the metal substrate and the resin is poor, the moisture adsorbed on the metal surface or the moisture absorbed at the adhesion interface in the manufacturing process expands, especially at high temperatures, and the surface of the metal substrate This promotes peeling between the resin and the resin, causes swelling and the like, impairs the internal corrosion resistance, cracks the resin in some cases, and destroys the wiring pattern.
[0004]
In order to improve the adhesion between the metal substrate and the resin, a method of roughening the metal surface and forming a so-called anchor has been used for a long time. In many cases, fineness generated during processing tends to impair the precision of electronic and electrical parts. Therefore, in practice, it is common to perform some kind of surface treatment on the metal substrate surface side.
[0005]
For example, a phosphating treatment is typical for steel materials, and a copper oxide treatment called “black dyeing” is typical for copper and copper alloys. The former is a method in which a heavy metal having a very small solubility product with tertiary phosphoric acid such as zinc is brought into contact with an acidic aqueous solution of phosphoric acid, and the latter is immersed in a strong alkaline aqueous solution containing an appropriate oxidizing agent and boiled. Is the method.
[0006]
However, since many of the films formed by the phosphate treatment have crystal water, the crystals are broken at a temperature of about 200 ° C. at the most, and the heat resistance of the film is inferior. Although the initial adhesiveness is good, since the durability is poor, the bonding strength decreases with time, and the initial adhesive force cannot be maintained even with heat treatment.
[0007]
On the other hand, in JP-A-9-209167 and JP-A-9-172125, the adhesion is improved by subjecting the surface of the metal substrate to chromate treatment. Furthermore, Japanese Patent Application Laid-Open No. 2000-183235 discloses a method of forming a special chromium compound layer having a large number of fine scaly projections on the surface using an electrolytic method.
[0008]
However, all of these methods use hexavalent chromium compounds that are harmful to the surface treatment liquid, and it is considered that hexavalent chromium is contained on the surface of the formed metal substrate. It is not preferable.
[0009]
[Problems to be solved by the invention]
The present invention is for solving the above-mentioned problems of the prior art, and the object of the present invention is to use a metal substrate and a resin without using a substance that causes environmental pollution such as hexavalent chromium. An object of the present invention is to provide a surface-treated film excellent in adhesion, particularly at high temperatures.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have paid attention to metallic nickel generally excellent in heat resistance and stability over time and nickel oxide formed on the surface thereof. Thus, by introducing a third element into them, a new nickel-based surface treatment film having excellent adhesion to the resin has been invented.
[0011]
That is, the present invention is a nickel-based surface treatment film having a two-layer structure formed on a target material, in which nickel and phosphorus are in a lower layer in contact with the surface of the material, and nickel, oxygen and phosphorus are in an upper layer. A nickel-based surface treatment film excellent in heat-resistant adhesiveness with a resin characterized by being contained.
[0012]
Further, boron can be used as an element instead of phosphorus contained in the nickel-based surface treatment film of the present invention.
[0013]
Moreover, phosphorus and boron may coexist as an element contained in the nickel-based surface treatment film of the present invention.
[0014]
Furthermore, it is more preferable that the content ratio of phosphorus and / or boron to nickel in the nickel-based surface treatment film is larger than that of the lower layer, that is, the following relationship is satisfied.
[(Phosphorus and / or Boron) / Ni] _{Lower Layer} <[(Phosphorus and / or Boron) / Ni] _{Upper Layer}
[0015]
Furthermore, it is more preferable that the upper layer of the nickel-based surface treatment film has a columnar structure, and a fine gap is provided between the columns of the columnar structure.
[0016]
The nickel-based surface treatment film of the present invention is preferably formed on copper or a copper alloy.
[0017]
The nickel-based surface treatment film of the present invention preferably has a gray, gray-black or black appearance.
[0018]
Hereinafter, the nickel-based surface treatment film of the present invention will be described in more detail.
[0019]
The nickel-based surface treatment coating of the present invention has a two-layer structure in which metallic nickel and phosphorus and / or boron are disposed on the lower layer in contact with the surface of the material, that is, a layer containing oxygen is further disposed on the upper layer. The target material is not particularly limited as long as the metallic nickel can be formed with sufficient adhesion to the target material. However, in the field of electronic / electrical components, particularly heat resistance adhesion between copper or a copper alloy and a resin is often required, so that description will be made mainly on copper as a target material.
[0020]
A cross-sectional scanning electron microscope (hereinafter referred to as SEM) image of the nickel-based surface treatment film of the present invention is shown in FIG. 1, and a surface SEM image is shown in FIG. Reference numeral 1 in FIG. 1 represents an upper columnar structure (including nickel, oxygen, and phosphorus) of the nickel-based surface treatment film of the present invention, and reference numeral 2 in FIG. 1 represents a lower layer (nickel) of the nickel-based surface treatment film of the present invention. In FIG. 1, reference numeral 3 denotes a copper substrate. FIG. 2 shows a surface SEM image (× 10000) of the nickel-based surface treatment film of the present invention.
As shown in FIG. 1, the upper layer of the surface treatment film of the present invention has a columnar structure, and a fine gap is observed between the columns (comb-like structure). Therefore, when this is observed from the surface (FIG. 2), it is observed as an extremely fine unevenness of an order of several tens to several hundreds of nanometers, and a very effective substantial surface area can be obtained at the time of adhesion to the resin. .
[0021]
According to the analysis by XPS, the upper layer nickel is in an oxidized state and the thickness thereof is about 500 nm. However, the oxide formed on the mere metallic nickel is a thin film, and the columnar shape as in the present invention. An organization is not formed. Such a form can be obtained by introducing the third element introduced in the present invention, that is, phosphorus and / or boron. Empirically, these third elements are preferably in the range of 2% to 50% by weight. If it is less than 2% by weight, such a form cannot be obtained, and if it exceeds 50% by weight, it is not difficult to form a nickel film having such a composition as the content increases. That is, it is economically disadvantageous.
[0022]
The height of the upper columnar structure of the nickel-based surface treatment film of the present invention is preferably in the range of 50 to 3000 nm. If the thickness is less than 50 nm, fine unevenness on the surface is not sufficiently formed, and if it exceeds 3000 nm, the unevenness becomes coarse. On the other hand, the thickness of the lower metallic nickel layer is not particularly limited. However, in order to sufficiently cover a part of the target material surface so as not to be exposed, it is preferably 0.5 μm or more. Moreover, since an unnecessary thick film is economically disadvantageous, it is sufficient that the upper limit of the film thickness is 5 μm.
[0023]
The appearance of the nickel-based surface treatment film of the present invention is gray, grayish black to black. This seems to be due to the fact that columnar structures with gaps absorb visible light as seen in FIGS. 1 and 2, which is particularly preferred in the field of electronic and electrical components. When the adhesion surface (surface treatment film surface of the present invention) is observed through the resin from the copper wiring pattern side, if it is black, the contrast with the pattern becomes clear, and the pattern inspection is optically performed. This is advantageous when done.
[0024]
The nickel-based surface treatment film of the present invention can be formed by forming a metallic nickel layer on a target material by various methods and then oxidizing the surface. The method for forming the metallic nickel layer can be a physical method such as PVD, but a wet surface treatment method such as an electroplating method or an electroless plating method is excellent in mass productivity. Hereinafter, a plating method for co-depositing the third element will be described.
[0025]
In order to eutect phosphorus as the third element, in the case of electroplating, for example, hypophosphorous acid or phosphorous acid may be further added to a well-known Watt bath. In the case of electroless plating, a commercially available type using hypophosphorous acid as a reducing agent may be used.
[0026]
Next, in order to eutectoid boron as the third element, an electroless plating bath using a boron-containing reducing agent such as DMAB (dimethylamine borane) may be used. Furthermore, when DMAB and hypophosphorous acid are simultaneously used as the reducing agent, phosphorus and boron can be co-deposited simultaneously. These are all commercially available.
[0027]
On the other hand, depending on the additive added to the plating solution, in addition to phosphorus and / or boron, carbon, nitrogen, sulfur and zinc can be co-deposited. In the sense of blackening, these methods work in a more preferred direction. For example, it becomes possible by introducing the additives described below.
[0028]
That is, to co-deposit nitrogen, aniline, monoethylamine, diethanolamine, dimethylamine, triethanolamine, nitrilotriacetic acid, pyridine, imidazole, morpholine, o-phenanthroline, glycine, glutamic acid, alanine, serine, hydrazine, aspartic acid Nitrogen-containing organic substances typified by ethylenediamine may be added. To co-deposit sulfur, N, N-diethyl-dithiocarbamate sodium, 1,3-diethyl-2-thiourea, methionine, ethionine, cystine, cysteine, glutathione, thioglycolic acid, saccharin, dipyridine, 1,2 , 3-Benzotriazole-2-thiazoline-2-thiol, thiazole, thiourea, thiozole, thioindoxylic acid, o-sulfonamidobenzoic acid, sulfanilic acid, methyl orange, naphthionic acid, naphthalene-α-sulfonic acid, 2 -A sulfur-containing organic compound such as mercaptobenzothiazole, sulfadiazine, or rhodanammon may be added. In order to eutect the zinc, a zinc compound such as zinc carbonate, zinc oxide, zinc chloride, or zinc sulfate may be added. Finally, in order to eutect the carbon, an amine organic compound typified by diethylenetriamine or the like may be added.
[0029]
When applying the above plating to copper and copper alloys, for example, in the case of electroplating, the copper surface may be cleaned and then directly electroplated, but hypophosphorous acid is reduced especially by electroless plating. In the case of using a bath as an agent, copper cannot be plated as it is because it has no catalytic activity for hypophosphorous acid. In such a case, a small amount of palladium plating may be applied as a pretreatment by palladium displacement plating or the like, or electroless nickel plating may be performed thinly (about submicron) as strike plating and then electroless nickel plating.
[0030]
After a predetermined nickel plating layer is formed on the target material, a columnar structure layer is formed on the surface. For this purpose, it is effective to carry out the treatment by contacting with an acid containing a suitable oxidizing agent. Specifically, a necessary amount of an oxidizing agent such as nitric acid, permanganic acid, ferric ion or hydrogen peroxide may be added to phosphoric acid, sulfuric acid or hydrochloric acid as a base. Alternatively, anodic electrolysis may be performed in the base acid aqueous solution. Even if such an oxide forming treatment is applied to a mere nickel metal surface, the surface morphology as in the present invention cannot be obtained, but the third elements including phosphorus introduced in the nickel-based surface treatment film of the present invention are In general, the metal nickel crystal is refined and further amorphized, but this refines the distribution state of the anode and cathode of the local battery formed by the oxidation treatment, resulting in the characteristics of the present invention. It seems that a typical surface columnar texture layer is created. In fact, according to analysis such as XPS, the upper layer has a higher content ratio of the third element including phosphorus to nickel than that of the lower layer. That is, it is suggested that nickel is preferentially dissolved by the oxidation treatment and phosphorus and the like remain. In addition, oxygen contained in the columnar structure of the upper layer is introduced along with such an oxidation treatment, and the content rate of the surface layer increases and decreases toward the lower layer.
[0031]
The resin bonded to the nickel-based surface treatment film of the present invention is not particularly limited, but epoxy resin and polyimide resin are frequently used in the field of electronic and electrical parts, and are the main object of the present invention. From the viewpoint of adhesion, a resin having a lower glass transition temperature is more convenient for adhesion because it can be softened at a higher temperature to reduce the difference in coefficient of thermal expansion between the metal and the resin. However, such a resin preferably has a high glass transition temperature because the heat resistance of the resin itself is lowered. The nickel-based surface treatment film of the present invention is empirically demonstrated particularly in such a resin having a high glass transition temperature.
[0032]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples of the present invention together with comparative examples.
[0033]
Example 1
The surface of a 300 × 200 × 0.5 mm copper plate (JISC1100) was plated with 1 μm of strike nickel using a Watt bath, and then immersed in an electroless plating bath prepared so that the phosphorus content was 9% by weight. Thus, an electroless Ni—P alloy layer having a thickness of 5 μm was formed. Furthermore, this was immersed in an oxidation treatment solution in which 75% phosphoric acid and 67.5% nitric acid were mixed at a volume ratio of 90:10 for 3 minutes at 40 ° C., and phosphorus was concentrated on the surface of the Ni—P alloy layer on the copper plate. A nickel layer was formed. The surface after the oxidation treatment had a beautiful black appearance with no gloss. When analyzing phosphorus in the depth direction by XPS, it was 35% by weight in the outermost layer and 8.8% by weight in the lower layer (the lower part of the columnar structure). Incidentally, FIGS. 1 and 2 are those of the first embodiment.
[0034]
Next, a polyimide adhesive (“Neoflex double-sided adhesive sheet” manufactured by Mitsui Chemicals) is laminated to a thickness of 50 μm on the nickel-based surface treated copper plate, and a 35 μm thick copper foil is disposed thereon. Then, press bonding was performed under the conditions of a pressing pressure of 50 kg / cm ² , a heating temperature of 250 ° C., and a heating time of 2 hours. This sample was cut into 50 mm squares, left in a heated and humid environment of 85 ° C. and 85% RH for 24 hours to promote deterioration, and then floated in a molten solder bath at 270 ° C. for 300 seconds or more. I was not able to admit.
[0035]
The details of the plating bath used in Example 1 and the processing conditions are described below. Strike nickel plating dissolves a reagent (using special grade) in deionized water so as to have a watt bath, that is, nickel sulfate: 330 g / L, nickel chloride: 45 g / L, boric acid: 38 g / L. Bath temperature: 50 ° C. The nickel plate was used as the anode, and the cathode current density was 5 A / dm ² . The electroless plating bath has a concentration of sodium hypophosphite: 0.15 mol / L, ammonium sulfate: 0.5 mol / L, trisodium citrate: 0.2 mol / L, nickel sulfate: 0.1 mol / L. Each was dissolved in deionized water, and caustic soda was further added to adjust the pH to 9. The thus prepared electroless Ni—P alloy plating bath was heated to 90 ° C. to perform electroless plating to form the Ni—P alloy layer.
[0036]
Example 2
The same test as in Example 1 was performed using the electroless Ni-B alloy plating bath shown below instead of the electroless Ni-P alloy plating bath. That is, as an electroless Ni—B alloy plating bath, the concentration of nickel chloride: 0.126 mol / L, DMAB: 0.06 mol / L, malonic acid: 0.378 mol / L, TINO ₃ : 70 mg / L. Each reagent was dissolved in deionized water, and the pH was adjusted to 6 with aqueous ammonia. The electroless Ni—B alloy plating bath adjusted as described above was heated to 70 ° C. and used. The boron content in the obtained Ni—B alloy film was 2.8% by weight. When this was oxidized in the same manner as in Example 1, a grayish black appearance was exhibited. Similarly, after bonding to a copper foil via a polyimide adhesive and placing it in a warm and humid environment, the solder heat resistance was examined. In 240 seconds, swelling occurred in the copper foil.
[0037]
Example 3
10 g / L of phosphorous acid was added to the Watt bath for strike plating used in Example 1, and cathode electrolysis was performed under conditions of a temperature of 40 ° C. and a current density of 5 A / dm ² , and Ni having a phosphorus content of 10% by weight. A 5 μm thick P alloy film was formed. When the oxidation treatment was performed by the same method as in Example 1, a beautiful black appearance was exhibited. Hereafter, when the same sample as Example 1 was produced and evaluated, abnormality was not recognized in 300 seconds in solder heat resistance.
[0038]
Comparative Example 1
The Ni strike plating watt bath used in Example 1 was used as it was, and after forming a 3 μm nickel plating, the same oxidation treatment as in Example 1 was performed. The appearance of. Hereinafter, when the same sample as Example 1 was produced and evaluated, the swelling occurred in 2 to 3 seconds, and the adhesive layer was peeled off.
[0039]
By applying the nickel-based surface treatment film of the present invention according to the above-described Examples 1 to 3, it is possible to obtain extremely good heat-resistant adhesion even after being exposed to, for example, a high-temperature wet environment by adhering to the resin. it can. On the other hand, it can be seen that good adhesion cannot be obtained by simply oxidizing the surface of the nickel film as in Comparative Example 1.
[0040]
【The invention's effect】
By applying the nickel-based surface treatment film of the present invention, when bonding a metal substrate and a resin, it is possible to impart wet resistance and excellent adhesiveness at high temperatures. High reliability can be brought about. Further, as an incidental effect, since the surface treatment film of the present invention has a dull black appearance, it gives a good contrast and improves inspection accuracy when optically inspecting electronic and electrical parts. be able to.
[Brief description of the drawings]
FIG. 1 shows a cross-sectional SEM image (× 3000) of a nickel-based surface treatment film of the present invention.
FIG. 2 shows a surface SEM image (× 10000) of the nickel-based surface treatment film of the present invention.
[Explanation of symbols]
1 Upper columnar structure of nickel-based surface treatment film of the present invention (including nickel, oxygen and phosphorus)
2 Lower layer of nickel-based surface treatment film of the present invention (including nickel and phosphorus)
3 Copper substrate

Claims (6)

A nickel-based surface treatment film having a two-layer structure formed on a target material, wherein a layer containing nickel and phosphorus in a lower layer in contact with the surface of the material is used as an upper layer , the lower layer surface is nitric acid, Nickel, oxygen and phosphorus formed by oxidizing with a kind of aqueous acid selected from phosphoric acid, sulfuric acid and hydrochloric acid containing a kind of oxidizing agent selected from permanganic acid, ferric ion and hydrogen peroxide A nickel-based surface-treated film excellent in heat-resistant adhesion to a resin , comprising a columnar structure, and having a layer having a fine gap between columns of the columnar structure . A nickel-based surface treatment film having a two-layer structure formed on a target material, a layer containing nickel and boron in a lower layer in contact with the surface of the material , and the lower layer surface as nitric acid, Nickel, oxygen and boron formed by oxidation treatment with a kind of aqueous acid selected from phosphoric acid, sulfuric acid and hydrochloric acid containing a kind of oxidizing agent selected from permanganic acid, ferric ion and hydrogen peroxide A nickel-based surface-treated film excellent in heat-resistant adhesion to a resin , comprising a columnar structure, and having a layer having a fine gap between columns of the columnar structure . A nickel-based surface treatment film having a two-layer structure formed on a target material, wherein a layer containing nickel, phosphorus and boron is formed as a lower layer in contact with the surface of the material, and the surface of the lower layer is formed. Nickel and oxygen formed by oxidizing with a kind of aqueous acid selected from phosphoric acid, sulfuric acid and hydrochloric acid containing a kind of oxidizing agent selected from nitric acid, permanganic acid, ferric ion and hydrogen peroxide A nickel-based surface excellent in heat-resistant adhesion to a resin, characterized by containing phosphorus and boron, having a columnar structure, and having a layer having a fine gap between the columns of the columnar structure Treatment film. The content ratio of phosphorus and / or boron with respect to nickel in the nickel-based surface treatment film is larger than that in the lower layer, and has the following relationship. A nickel-based surface treatment film excellent in heat-resistant adhesiveness with the resin according to claim 1.
[(Phosphorus and / or Boron) / Ni] _{Lower Layer} <[(Phosphorus and / or Boron) / Ni] _{Upper Layer} A metal-resin assembly comprising a metal substrate and a resin, on which a nickel-based surface treatment film having the two-layer structure according to any one of claims 1 to 4 is formed on the surface of the metal substrate. A printed wiring board having the metal-resin bonded body according to claim 5.

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