JPH06235088A - Steel products for electronic parts and their production - Google Patents

Abstract

PURPOSE:To provide the steel products for electronic parts having good solderability by subjecting a steel blank material as anode to alkaline degreasing and acid electrolytic washing, then subjecting the blank material as cathode to electroplating after the alkaline degreasing and acid washing. CONSTITUTION:The steel blank material 2 is subjected as the anode to the alkaline degreasing and the acid electrolytic washing, by which calcium and fat and oil components are electrically stripped from the surface of the steel blank material 2. The steel blank material 2 is covered with gaseous oxygen and is passivated as an oxidized film is formed on its surface in this stage. The steel blank material 2 is, therefore, subjected as the cathode to the alkaline electrolytic degreasing, by which the oxidized film is reduced. Further, the oxidized film is removed by the acid dip washing. Tin or solder plating is then directly applied on, the blank material by electroplating, by which the steel products 1 for electronic parts are obtd. The steel products for electronic parts have the good solderability and sufficient plating adhesion even if the products are not subjected to ground surface plating of Ni, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steel material for electronic parts, which has a good solderability even after a long time has passed after solder plating, like a solder-plated lead steel wire plated with nickel or copper undercoat. And a manufacturing method thereof.

[0002]

2. Description of the Related Art Steel materials for electronic parts (commonly called iron materials) including lead wires, frames and cases are cheaper than copper materials such as copper wires and copper covered steel wires (CP or EF wires). In the dry method, a solid lubricant is used at the time of finish processing such as wire drawing or rolling, so that calcium and oil components remain on the surface thereof, which are carbonized by annealing. On the other hand, in the dry method for steel materials, the use of a liquid lubricant during the finish processing of wire drawing or rolling causes oil to remain mainly on the surface of the liquid lubricant.

Since impurities such as oil remain on the surface of the steel material, it is necessary to first perform base plating in order to form tin or solder (tin-lead alloy) plating on the steel material, which is a copper material. Different from This base plating is, for example, nickel strike plating of a wood bath, copper strike plating of a cyan bath or pyrophosphoric acid bath, or electroless nickel plating.

When nickel underplating is applied to a solder-plated lead steel wire for a resistor made of ceramic or the like, there is a defect that a diffusion layer of the nickel and tin is brittle and easily peeled off. On the other hand, for copper wire and copper-clad steel wire, the price of the lead wire fluctuates according to the copper market price because the price is set based on relatively expensive copper, and if the copper base rises, the price of the lead wire also There is a problem of rising.

Recently, as in Japanese Examined Patent Publication No. 3-54405, a method of applying solder plating on tin strike plating (flash plating) as a base plating has been developed. The lead steel wire manufactured by this method has relatively good solderability even after a long time has passed after solder plating, but it requires plating twice.

[0006]

The lead steel wire which has been subjected to the solder plating by the above-mentioned methods requires the undercoating after the conventional pretreatment process of immersion degreasing → alkali electrolytic degreasing → acid immersion cleaning, If this undercoating is omitted, the scale on the steel surface is not sufficiently removed, resulting in poor adhesion of the solder plating and poor solderability. When manufacturing a steel material to be subjected to solder plating, adding the step of forming the base plating increases the number of steps as a whole, and the advantage that the steel material is less expensive than copper wire or copper-clad steel wire almost disappears. .

The present invention has been proposed in order to improve the above-mentioned problems relating to the production of lead steel wires for electronic components, and solder plating that has good solderability and solder wettability in accelerated deterioration tests and the like. It is intended to provide a single lead steel material. Another object of the present invention is to provide a method for producing a steel material for electronic parts, which is capable of directly applying tin or solder plating to a steel material by an electroplating method by further improving plating pretreatment.

[0008]

In order to achieve the above object, a steel material for electronic parts according to the present invention, for example, a lead steel wire 1
As shown in FIG. 1, the steel material 2 is formed by the electroplating method.
Then, a tin or solder plating layer 3 having a thickness of 1 to 50 μm is directly formed. This steel material includes lead frames, electronic component cases, etc. in addition to lead wires.

In the tin or solder plating layer 3, the composition of the solder plating layer is about 98 to 5% tin and about 2 to 95% lead. The steel material 2 includes products of iron or its alloys such as carbon steel and stainless steel.

In order to manufacture the steel material 1 for electronic parts, at least the steel material 2 is used as an anode for alkaline electrolytic degreasing cleaning and acid electrolytic cleaning, and then the steel material is used as a cathode for alkaline electrolytic degreasing cleaning and then acid immersion cleaning. . It is necessary to wash with water after each washing step.

The alkaline electrolytic degreasing cleaning using the steel material 2 as a cathode may be replaced with the alkaline electrolytic degreasing or acid electrolytic cleaning using the steel material as an anode. Generally, sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate is used for alkaline electrolytic degreasing, hydrochloric acid is used for acid electrolysis and acid immersion cleaning, and a surfactant or the like may be added to each cleaning solution.

In the method of the present invention, tin or solder plating is directly applied to the surface of the steel material 2 by the electroplating method.
As a tin or solder plating bath in the electroplating method, a borohydrofluoric acid bath, an alkanol sulfonic acid bath, a phenol sulfonic acid bath, a sulfamic acid bath or the like can be used as an organic acid bath.

[0013]

In the method of the present invention, oil and fat components are electrically stripped from the surface of the steel material 2 by alkaline electrolytic degreasing cleaning and acid electrolytic cleaning using the steel material 2 as an anode. In this process,
The steel material 2 is covered with oxygen gas and forms an oxide film on the surface to become a non-conductor. For this reason, alkaline electrolytic degreasing cleaning is performed using the steel material 2 as a cathode for reduction, and the oxide film is removed by acid immersion cleaning.

[0014]

EXAMPLES Next, the present invention will be explained based on examples. Example 1 A lead steel strand 2 having a diameter of 0.5 mm is pretreated according to the process illustrated in FIG. The cleaning liquid and cleaning conditions in this pretreatment are as follows.

1. Alkali immersion degreasing cleaning Sodium hydroxide 15% Surfactant 10% Liquid temperature 40-50 ° C

2. Alkaline electrolytic degreasing cleaning (+) Sodium hydroxide 15-20% Surfactant 2-5% Anode lead Steel element wire 2 Cathode Iron plate

3. Acid electrolysis cleaning Hydrochloric acid 15-20% Anode lead Steel element wire 2 Cathode Iron plate

4. Alkaline electrolytic degreasing cleaning (-) Sodium hydroxide 15-20% Surfactant 2-5% Anode iron plate Cathode Lead steel element wire 2

5. Acid immersion cleaning hydrochloric acid 20-30%

The pretreated lead steel wire 2 is
Alternatively, it is dipped in an electroplating bath of the second bath composition to contain lead 3% and tin 9%.
A solder plating layer 3 having a thickness of 7% and a thickness of 12 μm is formed. (First bath composition) Stannous borofluoride 350 g / l Lead borofluoride 30 g / l Borofluoric acid 220 g / l Semi-brightener 65 ml / l Dispersant 50 g / l

(Second bath composition) Stannous alkanol sulfonate 360 g / l Lead alkanol sulfonate 20 g / l Free acid 100 g / l Brightener and dispersant 60 ml / l

Example 2 A lead steel element wire 2 pretreated in the same manner as in Example 1 was immersed in an electroplating bath having the above bath composition, and a solder plating layer 3 having a lead content of 3% and a tin content of 97% and a thickness of 8 μm. To form.

Comparative Example 1 The lead steel wire used in Example 1 is cleaned by immersion degreasing → alkali electrolytic degreasing (−) → acid immersion as in the conventional case. The pretreated lead steel wire was immersed in the same electroplating bath as in Example 1, and had a thickness of 12 μm containing 3% lead and 97% tin.
m solder plating layer is formed.

Comparative Example 2 The lead steel wire used in Example 1 is treated in the same manner as in Comparative Example 1 to form a solder plating layer having a thickness of 8 μm and containing 3% lead and 97% tin.

Comparative Example 3 The lead steel wire used in Example 1 is washed by immersion degreasing → alkali electrolytic degreasing (−) → acid immersion as in the conventional case. The pretreated lead steel wire is subjected to copper strike plating of 1 to 2 μm, and further immersed in an electroplating bath in the same manner as in Example 1 to form a solder plating layer having a thickness of 12 μm and containing 3% lead and 97% tin. To do.

Comparative Example 4 The lead steel wire used in Example 1 was treated in the same manner as in Comparative Example 3 to form a solder plating layer having a thickness of 8 μm and containing 3% lead and 97% tin.

The solderability of the solder-plated lead steel wires obtained in both Examples and Comparative Examples is evaluated. This solderability was obtained by immersing each lead steel wire in a flux of 25% by weight of rosin and 75% by weight of IPA for 5 seconds and then immersing it in a eutectic solder bath of 62% tin and 38% lead held at a temperature of 235 ° C. The area dipped in solder for 2 seconds and wetted with solder is expressed as a percentage (%).

Table 1 below shows the normal state of the lead steel wire and the solderability after leaving it in a constant temperature bath at 170 ° C. for 24, 48 and 72 hours, with an average value of 5 pieces each.

[0029]

[Table 1]

Further, the solderability of each lead steel wire in a constant temperature and humidity test at 85 ° C. and 85% RH is also disclosed. Table 2 below shows the normal state and 25
It is an average value of 5 pieces each showing solderability after being left for 0,500 hours.

[0031]

[Table 2]

Next, the solder wettability of each lead steel wire is evaluated. This solder wettability is determined by immersing a lead steel wire with a length of 2 mm in the same flux as above for 5 seconds and then in a eutectic solder bath maintained at 235 ° C for 7 seconds, until the solder liquid surface becomes parallel. (Zero cross time) is measured with a solder graph and expressed in seconds.

Solder wettability is 105 ° C., 100% R
H, 1.2 atm pressure cooker test (hereinafter P
(Referred to as CT). In Table 3 below, the normal state of the lead steel wire and the solder wettability after standing for 16, 24, and 48 hours after PCT are shown as an average value of 5 pieces each.

[0034]

[Table 3]

As is clear from Tables 1 to 3, Example 1
The solder-plated lead steel wires 1 and 2 had better solderability after the heating and constant temperature and humidity tests than the lead steel wires of Comparative Examples 1 and 2, and the solder wettability after the PCT accelerated deterioration test. Is also excellent. The solder-plated lead steel wire 1 of Examples 1 and 2 has substantially the same performance as the solder-plated lead steel wire after the copper strike in Comparative Examples 3 and 4.

Comparing Examples 1 and 2, as the thickness of the solder plating tends to decrease, the quality decreases a little when the plating thickness becomes thin. This is the same in Comparative Examples 1 and 2 or Comparative Examples 3 and 4. Therefore, the solder-plated lead steel wire 1 of Examples 1 and 2 can be stored as an electronic component for a long period of time and sufficiently satisfies the quality as an electronic component.

[0037]

EFFECTS OF THE INVENTION The steel material for electronic parts according to the present invention has good solderability and sufficient plating adhesion even without undercoating of nickel or the like, and accelerated deterioration such as in PCT and heating test. The solder wetting rate after the test is also excellent, and it can be stored for a long time as an electronic component. Since the solder-plated steel material of the present invention has substantially the same performance as the solder plating after copper strike, an inexpensive steel material can be used in a material for electronic parts such as lead wires, and expensive copper need not be used. .

As a result, the solder-plated steel material of the present invention is
It can be provided to the electronic component industry at a stable and low price without becoming dependent on the copper market price such as copper wire and copper-clad steel wire, and the price does not fluctuate according to the copper market price. Further, the solder-plated steel material of the present invention is also used for a resistor made of ceramic or the like, and eliminates the defect that it is brittle and easily peeled off, as in the case of nickel underplating.

Further, in the method of the present invention, oil and fats and the like are electrically stripped from the surface of the steel material by alkaline electrolytic degreasing cleaning and acid electrolytic cleaning using the steel material as an anode, and an oxide film is formed on the surface in this step. Then, the steel material that has been rendered non-conductive is used as a cathode, and alkaline electrolytic degreasing cleaning is performed to reduce it. In the method of the present invention, the oxide film is finally completely removed by acid immersion cleaning, and hydrochloric acid is usually used for acid immersion cleaning to assist the initial electrodeposition of electroplating.

In the method of the present invention, the step of forming the base plating can be omitted in the production of the steel material and the solder plating can be directly applied, and the number of plating steps is small as a whole. Therefore, the method of the present invention can surely maintain the advantage that the steel material is less expensive than the copper wire or the copper-clad steel wire, and can provide the steel material for electronic parts whose quality is almost at the same level as the present.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing a steel material for electronic parts according to the present invention.

FIG. 2 is a flowchart illustrating a manufacturing process of a steel material for electronic parts of the present invention.

[Explanation of symbols]

 1 Lead steel wire 2 Steel material 3 Solder plating layer

Claims (2)

[Claims] 1. The steel material includes a lead wire, a lead frame,
Including an electronic component case, etc., the calcium content and the oil content are almost completely removed from the surface of the steel material to directly form a tin or solder plating layer having a thickness of 1 to 50 μm on the steel material by the electroplating method. Steel for electronic parts that has a solderability of 95% or more after being left for 72 hours. 2. At least a steel material is used as an anode for alkaline electrolytic degreasing cleaning and acid electrolytic cleaning. Further, the steel material is used as a cathode for alkaline electrolytic degreasing cleaning, followed by acid immersion cleaning, and then the surface of the steel material is electroplated. A method for manufacturing a steel material for electronic parts, which is directly plated with tin or solder.