JP5137317B2 - Electronic components - Google Patents

Description

  The present invention relates to a surface treatment agent for Sn and an Sn alloy, and a surface treatment method using the same. Furthermore, the present invention relates to an electronic component treated by the surface treatment method, an Sn alloy solder ball, an Sn alloy solder powder, a ball grid array using the solder ball, a solder paste using the solder powder, It relates to the mounted product used.

  Soldering is a technique for joining objects using a material having a relatively low melting point, and is widely used in joining and assembling electronic devices in the modern industry. The commonly used solder is Sn—Pb alloy, and its eutectic composition (63% Sn—remainder Pb) has a melting point as low as 183 ° C., so the soldering is performed at 220 to 230 ° C. As a result, almost no thermal damage is caused to the electronic components and the substrate. In addition, the Sn-Pb alloy has excellent characteristics that it has good solderability and is solidified immediately during soldering, and hardly cracks or peels even if vibration is applied to the soldered portion. .

In general, an electronic device is formed of a synthetic resin such as an outer frame or a substrate and a metal such as a conductor or a frame. When discarded, the electronic device is not incinerated and mostly buried in the ground. In recent years, rain on the ground tends to be acidic (acid rain), and it has become a problem that the solder of electronic devices buried in the ground is eluted to contaminate groundwater. For this reason, particularly in the electronic equipment industry, an alternative movement to lead-free solder (lead-free solder) is rapidly progressing.

  External lead terminals of electronic components are mainly subjected to solder plating (90% Sn-remainder Pb) in order to improve solder wettability and corrosion resistance, and it is desired to cope with lead-free. . Candidates for lead-free solder plating are broadly divided into pure Sn, Sn-Ag (Cu), Sn-Zn, and Sn-Bi, but each has its merits and demerits to completely replace Sn-Pb alloys. Has not yet reached.

  Pure Sn plating is considered to be the most powerful lead-free plating in terms of cost and workability of plating. However, Sn plating has a problem that solder wettability tends to deteriorate with time in addition to the fact that whiskers are likely to occur due to surface oxidation and internal stress, and there is a strong demand for improvement.

  The Sn—Zn alloy is advantageous in that it does not need to change current facilities and processes because it has a melting point close to that of a conventional Sn—Pb alloy. Moreover, it is excellent in the mechanical strength of a plating film, and is excellent also in cost. However, since Zn is an active metal species, it is likely to be oxidized, and Sn—Zn-based alloys have a very poor solder wettability due to oxidation. ing.

  Solder paste is used to surface-mount electronic components on a substrate, and the amount of use has increased in recent years. The solder paste is generally composed of a solder alloy powder as a main component and added with a flux containing an adhesive, an activator, a thixotropic agent, a surfactant, a solvent, and the like. As a lead-free solder paste, Sn—Ag (Cu) alloy, Sn—Zn alloy, and Sn—Bi alloy have been studied. As described above, Sn—Zn alloy is a conventional Sn—Pb alloy. Because it is close to the eutectic temperature of a solder, it is considered as a promising alternative candidate. However, because of the ease of oxidation of Zn as described above, the solder paste using the Sn—Zn alloy as the solder powder causes an oxidation reaction with the activator contained in the flux, and the solder wettability and storage stability are remarkably poor. In addition, there is a disadvantage that an inert gas atmosphere is required during reflow.

  In order to cope with these problems, the present inventors have disclosed, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-137574), one or two acidic phosphate esters having a saturated or unsaturated alkyl group and salts thereof. A surface treatment agent characterized by containing was proposed.

  Patent Document 2 (Japanese Patent Laid-Open No. 7-188942) proposes an antioxidant characterized in that it is composed of phosphoric acid diphenyl ester and / or phosphorous acid diphenyl ester.

  However, the phosphoric acid ester or phosphite ester in the above technique cannot obtain a sufficient antioxidant effect because the ester bond is decomposed by heat treatment at a relatively high temperature (200 ° C. or higher). For this reason, it has been difficult to prevent the oxidation of Sn and Sn alloy materials corresponding to lead-free solder, in which the soldering temperature is generally higher than in the prior art.

For the purpose of preventing this high temperature oxidation, the present inventors disclosed in Patent Document 3 (Japanese Patent Application No. 2004-061635) a compound having two or more phosphonic acid groups in one molecule and no ester bond in the molecule, and A surface treatment agent containing at least 0.01 g / L of one or more of its salts in total has been proposed.
However, since this surface treatment agent exhibits the maximum effect in a strong acid region (pH 2 or less), it has been difficult to apply it to parts made of materials that are vulnerable to acids such as chip capacitors.
JP 2004-137574 A Japanese Patent Laid-Open No. 7-188942 Japanese Patent Application No. 2004-061635

  The present invention can be applied to parts made of a material that is weak against acid, and an object thereof is to provide a surface treatment agent that imparts oxidation resistance to Sn and Sn alloy and improves solder wettability. Furthermore, an object of this invention is to provide the surface treating agent which suppresses generation | occurrence | production of the whisker of Sn and Sn alloy.

  Therefore, as a result of intensive studies, the present inventor imparts oxidation resistance even in a pH range of 3 to 5 by surface-treating Sn and Sn alloy with a surface treatment agent containing 0.01 g / L or more of tannic acid. And found that the solder wettability is improved. Further, the solder paste containing the Sn alloy subjected to the surface treatment showed a remarkable improvement effect on the storage stability. Furthermore, it was confirmed that the generation of whiskers was significantly suppressed from the Sn and Sn alloy plating subjected to this surface treatment.

That is, the present invention is as follows.
(1) It is characterized by containing 0.01 g / L or more of tannic acid for performing a surface treatment of the Sn or Sn alloy surface after the Sn or Sn alloy plating is performed on the conductor surface of the connection terminal portion of the electronic component. An electronic component that is surface-treated with a surface treatment agent.

By surface-treating Sn or Sn alloy with a surface treatment agent containing 0.01 g / L or more of tannic acid, oxidation resistance can be imparted and solder wettability can be improved.
Moreover, the storage stability of the solder paste containing the Sn alloy solder powder subjected to the surface treatment using the surface treating agent of the present invention is remarkably improved. Furthermore, by processing Sn and Sn alloy plating using the surface treating agent of the present invention, the generation of whiskers can be significantly suppressed.

The surface treatment agent of the present invention is described in detail below.
Examples of the metal to be treated with the surface treating agent of the present invention include Sn and Sn alloy. As the Sn alloy, an Sn alloy containing no lead is more preferable from the viewpoint of environmental pollution. Examples of the Sn alloy not containing lead include a solder alloy containing one or more of Zn, Bi, Cu, In, Ag, and Sb in Sn.

The surface treating agent of the present invention can be used by dissolving tannic acid in a solvent.
Tannin is a polyhydric phenol component usually contained in plants such as gallic and pentaploid, and is a compound having a plurality of OH groups in one benzene ring. In the present invention, tannin and / or a derivative thereof is used. Including tannic acid. As tannins, hydrolyzable tannins such as gallic tannin, pentaploid tannin, turkey tannin, sumac tannin, and condensed tannins such as kepracho tannin and walt tannin are effective for this application, but Sn and Sn alloys From the viewpoint of reactivity, it is desirable to use hydrolyzed tannin.
Tannic acid has a complex structure, and therefore has a relatively high decomposition temperature (225 to 235 ° C.) and high heat resistance. Accordingly, the heat resistance is superior to the case of using phosphate ester or phosphite ester.

  The solvent used is not particularly limited as long as it is soluble. For example, water and polar solvents such as alcohol and glycol can be mentioned, but water is preferable in consideration of solubility, cost and the like.

By surface-treating Sn or an Sn alloy with a surface treatment agent containing 0.01 g / L or more of tannic acid, it is possible to impart oxidation resistance to the surface of the material to be treated and improve solder wettability.
The effect is small when the amount of tannic acid is less than 0.01 g / L. On the other hand, if the amount added is too large, the properties will not deteriorate, so there is no upper limit for the amount added. However, from the viewpoint of cost, the amount added is preferably 0.01 to 500 g / L, more preferably 0. .1 to 100 g / L.

  When an aqueous solvent is used, the pH of the surface treatment agent is preferably pH 3 to 5 and more preferably pH 3 to 4 in view of the influence on the material and the like. When pH exceeds 4, it becomes easy to decompose | disassemble, but it can suppress by adding antioxidant. As the pH adjuster, generally available acids and alkalis can be used.

As described above, the surface treatment agent of the present invention can suppress decomposition of tannic acid by adding an antioxidant (solution stabilizer). The antioxidant is preferably added in an amount of 5 wt% or more based on the amount of tannic acid. When the addition amount of the antioxidant is less than 5 wt% of the tannic acid, the effect of suppressing the decomposition of tannic acid due to the addition cannot be obtained. The addition amount of the antioxidant is preferably 5 to 20 wt% with respect to the amount of tannic acid.
As the antioxidant, a normal antioxidant can be used, for example,
1) dl-α-tocopherol having a phenolic hydroxyl group in the molecule, dibutylhydroxytoluene, butylhydroxyanisole, gallic acid and the like, ascorbic acid derivatives such as L-ascorbic acid and L-ascorbic acid stearate, erythorbic acid, Eliminate radicals and active oxygen such as sodium erythorbate and L-cysteine hydrochloride
2) Strong inorganic reducing action such as potassium pyrosulfite, sodium pyrosulfite, sodium sulfite, sodium hyposulfite, sulfur dioxide,
3) Some have strong chelating action such as disodium ethylenediaminetetraacetate, disodium ethylenediaminetetraacetate, isopropyl citrate and the like.

  In addition, the surface treatment agent of the present invention may contain an amount of an additive in a range that does not impair the original properties for the purpose of imparting desired performance. Examples of the additive include preservatives and pH buffering agents, and conventionally known additives can be used.

In order to surface-treat Sn or Sn alloy using the surface treatment agent of the present invention, any method can be used as long as it is a method of forming a film on the surface of Sn or Sn alloy. For example, Sn or Sn alloy is simply immersed in the surface treatment agent. And a method of applying the surface treatment agent using a shower or a device such as an air coater, a blade coater, a rod coater, a knife coater, a gravure coater, a reverse coater, and a cast coater.
The temperature of the solution for the surface treatment is preferably 20 to 60 ° C., more preferably 30 to 50 ° C. from the viewpoint of reactivity, equipment heat resistance temperature and workability when used in an aqueous system.

The shape of the metal surface-treated with the surface treatment agent of the present invention may be any shape such as linear, plate / strip / foil, granular, powder, etc. The surface treatment agent of the present invention is an electronic component. Solder balls, solder powder, etc. can be processed. The electronic component in the present invention includes a substrate.
The surface treatment agent of the present invention is used to surface-treat the conductor surface of the connection terminal portion of the electronic component, or after plating the conductor surface, it is excellent in oxidation resistance and solder wettability. It can be an improved electronic component. Moreover, solderability is also improved by improving solder wettability.
Solder balls using an Sn alloy treated with the surface treating agent of the present invention have excellent oxidation resistance, and are arranged on electronic components as a ball grid array which is an electrical connection member, and this is connected to a circuit board. It can be used satisfactorily as a mounted product.

  Further, the Sn alloy powder can be treated with the surface treating agent of the present invention, and a flux containing an adhesive, an activator, a thixotropic agent, a surfactant, a solvent and the like can be added thereto to be used as a solder paste. This solder paste has a remarkable improvement effect on its storage stability. Conventionally known pressure-sensitive adhesives, activators, thixotropic agents, surfactants and solvents can be used.

Hereinafter, the present invention will be described in detail with reference to examples.
Examples 1-7 and Comparative Example 1
Seven types of isopropyl alcohol (IPA) solutions or aqueous solutions mainly containing tannic acid (tannic acid AL, manufactured by Fuji Chemical Industry Co., Ltd.) were prepared (Examples 1 to 7). The breakdown is shown in Table 1.
On the other hand, the following pretreatment was performed on the copper material (C1020P, 10 mm × 25 mm × 0.2 ^t mm).
Alkaline electrolytic degreasing (room temperature, 15 A / dm ² , treatment for about 30 seconds) → water washing → acid immersion (10% sulfuric acid, room temperature, 5 seconds) → water washing → chemical polishing (CPB-40, room temperature, 1 minute immersion) → water washing → Acid soaking (10% sulfuric acid, room temperature, 5 seconds) → Washing This substrate was Sn plated with a film thickness of about 5 μm (plating bath: Tincoat K (manufactured by Nikko Metal Plating Co., Ltd.)), plating Conditions: cathode current density 2 A / dm ² , temperature 20 ° C., liquid flow and cathode swing plating).

  The substrate subjected to Sn plating (hereinafter referred to as “Sn substrate”) was immersed in the above alcohol solution at room temperature for 10 seconds and then dried to obtain a test substrate (Examples 1 and 2). On the other hand, the Sn substrate was immersed in the above aqueous solution at a bath temperature of 40 ° C. for 10 seconds, then washed with water and dried to obtain a test substrate (Examples 3 to 7).

The following evaluations were performed on these test substrates.
Further, as a comparative example, the untreated Sn base material (Comparative Example 1) was also evaluated.
Thermal oxidation resistance These test boards were heat-treated in an electric furnace maintained at 220 ° C. for 1 hour in air, and then solderability with lead-free solder (zero cross time) was measured by the meniscograph method based on the following measurement conditions And evaluated according to the following criteria.
Equipment: Solder Checker SAT-5100 (Resca)
Solder bath; tin: silver: copper = 96.5: 3: 0.5 (bath temperature 245 ° C.)
Flux; NA-200 (manufactured by Tamura Kaken)
Immersion depth: 2mm
Immersion speed: 4 mm / sec.
Immersion time: 5 sec.
Evaluation criteria A: Zero cross time less than 1 second ○: Zero cross time 1 second or more and less than 3 seconds Δ: Zero cross time 3 seconds or more and less than 5 seconds X: Zero cross time 5 seconds or more Table 1 shows the test results.

Moisture oxidation resistance These test substrates were subjected to PCT treatment (left in a sealed kettle with a temperature of 105 ° C and a humidity of 100% for 16 hours) and then soldered with lead-free solder (zero cross time) by meniscograph method Measured and evaluated in the same manner as in the section of heat and oxidation resistance. Table 1 shows the test results.

Solution Stability The solutions prepared in Examples 1 to 7 were placed in a screw cap bottle, the lid was closed, and the solution was immersed in a water bath maintained at 40 ° C. to confirm deterioration of the solution over time (generation of precipitation). The results are also shown in Table 1.

Examples 8 to 13 and Comparative Example 2
The copper material (C1020P, 10 mm × 25 mm × 0.2 ^t mm) subjected to the same pretreatment as in Examples 1 to 7 was subjected to Sn—Zn plating with a film thickness of about 5 μm (plating bath: Nikko Metal) Plating Co., Ltd., plating conditions: cathode current density 3 A / dm ² , temperature 35 ° C., pH 4.0, liquid flow and cathode swing plating).
The substrate subjected to Sn—Zn plating (hereinafter referred to as “Sn—Zn substrate”) was dipped in the alcohol solution prepared in Examples 1 and 2 at room temperature for 10 seconds, and then dried and used as a test substrate. (Examples 8 and 9). On the other hand, the Sn—Zn base material was immersed in the aqueous solutions prepared in Examples 3, 4, 6, and 7 at a bath temperature of 40 ° C. for 10 seconds, washed with water, and dried, together with the test substrate. (Examples 10 to 13).
With respect to these test substrates, in the same manner as in Examples 1 to 7 and Comparative Example 1, the heat oxidation resistance and the moisture oxidation resistance were evaluated. The test results are shown in Table 2.

  Further, as a comparative example, the untreated Sn—Zn base material (Comparative Example 2) was also evaluated. The test results are also shown in Table 2.

Example 14 and Comparative Example 3
Example 14 shows a result in which whisker generation of the surface-treated Sn plating was significantly suppressed as compared to the case where the surface treatment was not performed.
The Sn-plated substrate treated in the same manner as in Example 2 and the substrate not subjected to surface treatment were left for 24 hours in a constant temperature and humidity atmosphere at a temperature of 85 ° C. and a humidity of 85%. Then, after fully drying the substrate, the surface was observed with a scanning electron microscope (SEM). When the surface treatment was not performed, many whiskers were observed (Comparative Example 3), whereas the surface treatment was performed. No whiskers were observed from those subjected to (Example 14).

Example 15 and Comparative Example 4
In Example 15, the storage stability of the paste using the surface-treated Sn-9% Zn alloy powder is shown to be significantly suppressed as compared to the case where the surface treatment was not performed.
A 1 wt% isopropanol solution containing tannic acid as an active ingredient (the same solution as in Example 2) was prepared, and surface treatment was performed on Sn-9% Zn solder powder (particle size: 25 to 45 μm).
This surface-treated solder powder and flux were well mixed at a weight ratio of 9: 1 to obtain a solder paste. The flux includes 30 parts of polymerized rosin, 30 parts of hydrogenated rosin, 30 parts of glycol solvent, 5 parts of activator (organic acid having 1 to 30 carbon atoms and amine hydrobromide), thixotropic agent (cured castor) Oil) Flux for solder paste using 5 parts was used.
When the storage stability was evaluated by refrigerated storage at 5 ° C., the solder paste made of untreated powder solidified after one week, and the viscosity became unmeasurable (Comparative Example 4). The solder paste according to No. 3 showed no significant difference in viscosity even after 3 months (Example 15).

Example 16 and Comparative Example 5
In Example 16, the storage stability of the paste using the surface-treated Sn-3% Ag-0.5% Cu alloy fine powder is shown to be significantly suppressed as compared with the case where the surface treatment was not performed.
A 1 wt% isopropanol solution containing tannic acid as an active ingredient (the same solution as in Example 2) was prepared, and surface treatment was performed on Sn-3% Ag-0.5% Cu solder powder (particle diameter 5-15 μm).
This surface-treated solder powder and the solder paste flux used in Example 15 were well mixed at a weight ratio of 9: 1 to obtain a solder paste.
When the storage stability was evaluated by refrigerated storage at 5 ° C., the solder paste made of untreated powder solidified after 2 weeks, and the viscosity became unmeasurable (Comparative Example 5). The solder paste according to No. 3 showed no significant difference in viscosity even after 3 months (Example 16).

Example 17 and Comparative Example 6
In Example 17, the oxidation resistance performance of the solder balls using the surface-treated Sn-3% Ag-0.5% Cu alloy is shown to be remarkably improved as compared with those not subjected to the surface treatment.
A 1 wt% isopropanol solution containing tannic acid as an active ingredient (the same solution as in Example 2) was prepared, and surface treatment was performed on Sn-3% Ag-0.5% Cu solder balls (particle diameter 600 μm).
The surface-treated solder balls and untreated solder balls were heat-treated in an air atmosphere for 1 hour in an electric furnace maintained at 220 ° C., and then Sn-plated substrate produced in Example 1 based on the following measurement conditions The reflow process was performed above.
Reflow conditions: 260 ° C x 30 seconds (implemented on a hot plate)
Flux: NA-200, manufactured by Tamura Chemical Co., Ltd. Each solder part was photographed from above, the wet spread area of the solder part was calculated, and the wet spread characteristic of the solder ball was evaluated. Table 3 shows the results.

Claims (1)

  A surface comprising 0.01 g / L or more of tannic acid for performing Sn or Sn alloy plating on a conductor surface of a connection terminal portion of an electronic component and then performing surface treatment of the Sn or Sn alloy surface An electronic component that is surface-treated with a treating agent.