JP3142754B2 - Lead frame for electroacoustic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for connecting internal elements of an electro-acoustic transducer such as a sounder, a speaker, a microphone, an earphone, a pickup, a magnetic head and the like and for connecting with an external element. It is.

[0002]

2. Description of the Related Art For example, a sounder which is a kind of an electroacoustic transducer will be described. As shown in FIG. 4, a lead frame 1 is a molded body formed by etching or punching a metal base material. The lead terminal 6
A, 6B, 6C, and 6D are used as inner lead portions, and are shown on the inner lead portion as shown by imaginary lines in FIG. 4 (not shown).
A base member in which a base member including a pole piece portion is molded from a synthetic resin is integrally formed, and a terminal of a coil installed in the pole piece on the base portion is connected to a lead terminal, and then a resonance chamber is formed. A package of an electroacoustic transducer is formed by bonding a synthetic resin case to the base portion to cover the base portion, and further, externally connecting the outer lead portions 7A, 7B, 7C and 7D of the lead terminals by bending at 90 °. The electroacoustic transducer is completed by configuring the terminals for use. In the drawing, reference numeral 5 denotes a guide hole for processing the lead frame and forming the lead frame 1. The external connection terminal is an important part to be soldered to the surface mounting substrate.

Recently, lead frames (hereinafter referred to as "frames") of such electroacoustic transducers have recently been made of Cu--Zn (for example, Cu-30% Zn, Cu-40% Zn), Cu
-Sn-based alloys (e.g., Cu-4% Sn-0.2% P) and the like (hereinafter abbreviated as "base material") have come to be used. As the above-described Cu-Zn-based and Cu-Sn-based alloy frame materials, those having an elongation of 5 to 50% have been used in order to prevent cracks from occurring during bending. More specifically, for example, a plate of Cu-30% Zn-based alloy is plated with a Cu underlayer having a thickness of 1 μm,
The one subjected to bright solder plating of 7 μm to 7 μm is used as a frame. This bright plating is employed to improve the solderability of the base material. Also,
For example, a Cu-4% Sn-0.2% P alloy which is plated with a Ni underlayer having a thickness of 2 to 5 .mu.m and then a bright solder plating having a thickness of 5 to 7 .mu.m is also used as a frame. .

[0004]

The resin-encapsulation is performed using these plated frames, and the outer leads are bent at 90 ° in the final step. Fine cracks occur, and furthermore, when soldering on the board, these fine cracks cause deterioration of solder wettability due to aging in the bent part,
Insufficient soldering occurs during board mounting.

When a Cu—Zn alloy is used for a frame, Zn precipitates and diffuses in a solder plating layer during soldering,
It significantly impairs solder wettability. Similarly, when the outer lead portion of a frame in which a Cu—Sn-based alloy is subjected to solder bright plating is bent at 90 °, fine cracks are generated in the solder plating layer even if micro cracks do not occur in the base material, When the outer lead is joined to the lead of the external element at the time of mounting on the board, a soldering failure occurs.

[0006] Such poor soldering during board mounting is a major problem in terms of the reliability of the electroacoustic transducer. In other words, when analyzing the cause of failure of the electroacoustic transducer,
Since solder at the time of mounting did not flow into the cracked portion, there was a connection defect, which was found to be one of the causes.

[0007]

According to the present invention, as a result of various studies, a lead frame for an electro-acoustic transducer capable of manufacturing a highly reliable electro-acoustic transducer while performing economical plating on the frame has been developed. The growth rate is 20
% Of the frame formed from metal substrate strips,
Ni plating on the entire surface of the frame or at least the lead terminal portion with a plating solution containing no brightener,
It is characterized by being subjected to solder plating with a plating solution containing no brightener.

In the present invention, each plating is carried out without adding a brightener composed of an organic compound such as thiourea, saccharin or glucose or an inorganic compound such as thiosulfate to the Ni plating bath and the solder plating bath. This is because when the brightener is contained, the plating surface becomes bright and the plating structure becomes finer, and the plating film easily cracks when the frame is bent. The plating formed by the plating solution containing no brightener is hereinafter referred to as “matte plating”.

As the nickel plating solution, a normal bath, a Watts bath, a semi-bright bath, a sulfamic acid bath and the like can be used, and a Watts bath is particularly preferable. Similarly, as the solder plating bath, a borofluoric acid solder plating bath, a methanesulfonic acid bath, or the like can be used, but a methanesulfonic acid bath is preferable.

Further, in the present invention, the elongation percentage of the metal substrate strip alloy is set to 20% or more because a metal base having an elongation percentage of less than 20% is subjected to press forming or etching, followed by plating and then bending. This is because when processing is performed, cracks occur at the corners of the lead portions, and the underlying plating is oxidized due to aging, and the wettability of the solder deteriorates.

That is, according to the present invention, a metal substrate strip alloy having an elongation of 20% or more is formed into a frame by pressing or etching, and then, as shown in FIG. 0 μm, preferably 0.1 μm.
A matte Ni base plating having a thickness of from 05 to less than 0.3 μm is provided, and a coating layer of matte solder plating having a thickness of 1 to 10 μm, preferably 5 to 7 μm is provided thereon. Ni and solder plating may be applied to the entire surface of the frame, or at least to the lead terminal portion, and may be coated by electroplating to a desired thickness. As the solder, 90% Sn-10% Pb is particularly preferable.

In the present invention, Fe-3 is used as the metal substrate.
5.5-36.5% Ni alloy, Fe-40.5-41.
F such as 5% Ni, Fe-49.5-51.5% Ni alloy
e-Ni alloys and copper alloys such as brass, phosphor bronze, and phosphor bronze for springs are preferably selected, but have an elongation of 20% or more, and have good Ni base plating conformity and good solder wettability. If so, a metal substrate other than the above can be selected.

In order to increase the elongation of the Fe—Ni alloy to 20% or more, a step of reducing the rolling reduction (thickness reduction) of the temper rolling after the recrystallization annealing to 10% or less may be employed. Although elongation is further increased by performing strain relief annealing after the temper rolling, strain relief annealing at 500 to 600 ° C. is preferable in order to prevent a decrease in strength. Also, after rolling, temper annealing
Although elongation of 20% or more can be obtained by performing at 700 ° C., temper rolling has less variation in quality than temper annealing.

For the copper alloy, the rolling reduction of the temper rolling in recrystallization annealing is 20% or less for brass and 1 for general phosphor bronze.
5% or less, and 25% or less for phosphor bronze for spring,
By rolling, an elongation of 20% or more can be obtained.

[0015] The frame of the present invention has the above-described structure, and by setting the elongation percentage of the metal base material to 20% or more, the occurrence of cracks at the time of bending the lead terminal portion at 90 ° is prevented.
Further, the surface of the lead terminal portion mounted on the substrate is covered with Ni plating to prevent the diffusion of the constituent elements from the base material. In addition, Ni plating and solder plating coated on the base material are made to be matte plating, so that 90 °
Prevents the generation of fine cracks in the plated part due to bending.

However, the thickness of the dull Ni plating is 0.1 mm.
When the coating thickness is less than 0.01 μm, the effect as a diffusion barrier of alloying elements and impurity elements contained in the metal substrate under heating conditions at the time of sealing the synthetic resin is lost. If it exceeds, a greater effect cannot be obtained and it is uneconomical. The thickness of the Ni coating layer is preferably 0.05 to 0.3 μm.

[0017] When bright Ni plating is applied as in the conventional method, the electrodeposited nickel has a large strain and becomes microcrystalline, and as a result, is harder than a metal base material and has poor workability. Cracks occur during processing, leading to defects in the leads. Particularly in the case of an electroacoustic transducer, the bending of the outer leads has a radius (r) of 0.5 mm or less and a plate thickness (t).
Ratio (r / t) to 2.5 is strictly 2.5 or less, and excellent workability is required for the plating layer.

The thickness of the solder coating layer is 1 to 10
If the coating thickness is less than 1 μm, the soldering strength at the time of mounting on the board is insufficient, and if it exceeds 10 μm, the solder becomes excessive and uneconomical. The thickness of the solder coating layer is preferably 5 to 7 μm. The reason why the coating layer of the solder is matte plating is the same as the case of the Ni plating. Hereinafter, the present invention will be described in detail with reference to examples.

Preferred compositions and conditions for the matte plating bath of the present invention are as follows. A. Matte Ni plating bath composition Nickel sulfate: 200 g / L to 250 g / L Nickel chloride: 35 g / L to 45 g / L Boric acid: 20 g / L to 30 g / L pH: 4 to 5 Bath temperature: 40 to 55 ° C. Current density : 1 A / dm ^{2 to} 8 A / dm ² B. Matte solder plating bath composition Stannous fluoride: 80 g / L to 120 g / L Lead borofluoride: 20 g / L to 40 g / L Free hydrofluoric acid: 80 g / L to 120 g / L Free boric acid: 20 g / L to 30 g / L B naphthol: 0.5 g / L to 3 g / L Formalin: 8 g / L to 15 g / L pH: 4 to 5 Bath temperature: 15 to 30 ° C. Current density: 1 A / dm ^{2 to} 6 A / dm ²

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 0.2 m thickness, each having an elongation of 20%
m Fe-36% Ni alloy, Fe-42% Ni alloy, F
e-50Ni% alloy, brass, phosphor bronze specified in JIS H 3110, phosphor bronze for spring specified in JIS H 3130, a metal base plate strip having a width of 10 mm and a length of 100 in the rolling direction.
mm strip-shaped test pieces, which were used in Example 1 of the present invention.
６6 and subjected to the tests described below and evaluated.

Matte Ni plating was performed by the following method. (1) Bath composition Nickel sulfate 240 g / L Nickel chloride 45 g / L Boric acid 30 g / L pH 5.0 (2) Bath temperature 50 ° C. (3) Current density 5 A / dm ²

The matte solder plating was performed by the following method. (1) Bath composition Stannous borofluoride 80 g / L Lead borofluoride 10 g / L Free hydroboronic acid 100 g / L Free boric acid 25 g / L β-naphthol 1 g / L Formalin 20 g / L pH 5.0 (2) ) Bath temperature 25 ° C (3) Current density 3A / dm ²

Further, as a comparative example, a metal substrate of the same kind as the above having an elongation of less than 20% was taken as a comparative example, and the same thickness as that of the above was used.
A strip-shaped test piece having a size of 2 mm, a width of 10 mm and a length of 100 mm was prepared and subjected to an evaluation test.

The bright Ni plating was performed by the following method. (1) Bath composition Nickel sulfate 300 g / L Nickel chloride 50 g / L Boric acid 40 g / L Brightener (saccharin) 1.5 g / L pH 4.5 (2) Bath temperature 50 ° C. (3) Current density 5 A / dm ²

The bright solder plating was performed by the following method. (1) Bath composition Stannous borofluoride 150 g / L Lead borofluoride 50 g / L Free hydroboronic acid 100 g / L Free boric acid 25 g / L β-naphthol 1 g / L Formalin 20 g / L Brightener (amine aldehyde type 60 g / L pH 5.0 (2) Bath temperature 25 ° C. (3) Current density 3 A / dm ²

The alloy composition of the base material is as follows. Fe-36% Ni alloy: 36.1% Ni, 0.3% Mn, 0.1% Si, 0.003% C, balance FeFe-42% Ni alloy: 41.6% Ni, 0.5% Mn, 0.3% Si, 0.004% C, balance Fe Fe-50% Ni alloy: 49.8% Ni, 0.6% Mn, 0.4% Si, 0.003% C, balance Fe phosphorus Bronze (1): 3.8% Sn, 0.18% P, balance Cu phosphor bronze (2): 4.8% Sn, 0.20% P, balance Cu phosphor bronze (3): 6.1% Sn , 0.19% P, balance Cu phosphor bronze (4): 7.9% Sn, 0.21% P, balance Cu 70/30 brass (1): 30.5% Zn, balance Cu 70/30 brass ( 2): 35.8% Zn, balance Cu 70/30 brass (3): 37.5% Zn, balance Cu phosphor bronze for spring: 7.9% Sn, 0.20 P, the balance Cu

Using the test pieces described above, the following evaluation tests were performed assuming plating and board mounting. (1) Plating adhesion: After applying a predetermined base plating and 90% Sn-10% Pb solder plating to a metal substrate, bending 90 ° (inner radius 0.2 mm) in a direction parallel to rolling,
The presence or absence of plating peeling was observed.

(2) Solderability of plating: A test piece obtained by applying a rosin-alcohol-based flux to a test piece having a predetermined undercoating and solder plating applied to a metal substrate was heated at 230 ° C.
Was immersed in the 60% Sn-40% Pb solder for 5 seconds, and the solder wetting area was observed.

(3) Solderability after heat resistance test: A test piece obtained by subjecting a metal substrate to a predetermined undercoating and solder plating is bent at 90 ° in a direction parallel to the rolling direction, and then heated at 150 ° C for 24 hours.
After heating in air for an hour, soldering was performed by the method described in the above section (2). Tables 1 and 2 show the test results.

Each characteristic was evaluated by the following method. Adhesion of plating: The test piece was bent by 90 °, and the presence or absence of plating peeling was determined. Plating solderability: Solder wet area of 95% or more was accepted and less than 95% was rejected. Solderability after heat resistance test: Solder wet area of 95% or more was accepted, and less than 95% was rejected.

As is clear from Tables 1 and 2, Example No. 1 of the present invention. Nos. 1 to 6 are Comparative Example Nos. It can be seen that it has higher reliability in the mounted state as compared with 7 to 12. Comparative Example N
o. Even when phosphor bronze for springs having an elongation of 20% or more is used as shown in FIG. 12, corner cracks are observed in the plating layer in a 90 ° bending test when a bright Ni plating is applied, and solder wetting in a board mounting test is performed. It can be seen that the rejection rate is high and the reliability is poor.

[0032]

As described above, according to the frame of the present invention, a high reliability of an electroacoustic transducer can be manufactured by effectively exhibiting a high elongation rate of a metal substrate and characteristics of solder plating. It is. In addition, this frame requires a high elongation rate of the metal substrate and solder plating, and is expected to have a remarkable effect as a frame of an electronic component subjected to severe bending.

[Brief description of the drawings]

FIG. 1 is a table (Table 1) showing the structure and characteristics of a lead according to an embodiment of the present invention.

FIG. 2 is a table (Table 2) showing the structure and characteristics of a lead of a comparative example.

FIG. 3 is a sectional view showing a frame of the present invention.

FIG. 4 is a plan view of a press-molded frame of the present invention.

[Explanation of symbols]

 1 Frame 2 Metal substrate 3 Matte Ni plating coating layer 4 Matte solder plating coating layer 5 Guide hole 6 Lead terminal 7 Outer lead part of lead terminal (external terminal)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Sone 20-10 Nakayoshida, Shizuoka City, Shizuoka Prefecture Inside Star Seimitsu Co., Ltd. (72) Inventor Kazuyuki Suzuki 20-10, Nakayoshida, Shizuoka City, Shizuoka Prefecture (56) References JP-A-7-121184 (JP, A) JP-A-3-125396 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 9 / 02 C23C 28/02 G10K 9/13 101 H01L 23/48

Claims (6)

(57) [Claims] 1. A molded article of a metal substrate having an elongation of 20% or more, having a thickness of 0.01 formed by a plating solution containing no brightener.
To a thickness of 1 to 10 μm formed by a Ni underplating layer having a thickness of from 2.0 to 2.0 μm and a plating solution containing no brightener thereon.
A lead frame for an electroacoustic transducer, comprising: 2. The method according to claim 1, wherein the metal substrate is selected from the group consisting of an Fe—Ni alloy, brass, phosphor bronze, and phosphor bronze for a spring.
The lead frame for an electroacoustic transducer according to claim 1, which is a seed. 3. The lead frame for an electroacoustic transducer according to claim 1, wherein the metal substrate is an Fe—Ni alloy temper-rolled at a rolling reduction of 10% or less after recrystallization annealing. 4. The lead frame for an electroacoustic transducer according to claim 1, wherein said metal substrate is brass temper-rolled at a rolling reduction of 20% or less after recrystallization annealing. 5. The method according to claim 1, wherein the metal substrate is a general phosphor bronze that has been temper rolled at a rolling reduction of 15% or less after recrystallization annealing.
The lead frame for an electroacoustic transducer according to the above. 6. The lead frame for an electroacoustic transducer according to claim 1, wherein the metal substrate is a phosphor bronze for a spring temper-rolled at a rolling rate of 25% or less after recrystallization annealing.