JPH09135492A - Lead frame for electro-acoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in solderability or occurrence of a crack at bending processing of a lead terminal by applying Ni undercoat plating and solder plating to a lead frame with a plating liquid not containing a brightener. SOLUTION: The read frame 1 is a forming by etching or punching a metallic base, and an electroacoustic transducer is manufactured by using lead terminals 6A to 6d for inner leads and using bent outer leads 7a to 7b for external connection terminals. The lead frame 1 is formed by applying an Ni undercoat plating layer formed by a plating liquid not including a brightener and whose thickness is 0.01 to 2.0μm and a solder plating layer formed by a plating liquid not including a brightener and whose thickness is 1 to 10μm. Thus, production of very small cracks is prevented at 90 deg. bending processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component, and more particularly to a lead frame used for connecting internal elements and external elements of electroacoustic transducers such as sounders, speakers, microphones, earphones, pickups and magnetic heads. Is.

[0002]

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

The lead frame (hereinafter referred to as "frame") of such an electroacoustic transducer has recently been made of Cu-Zn system (for example, Cu-30% Zn, Cu-40% Zn), Cu.
Alloys such as -Sn system (e.g. Cu-4% Sn-0.2% P) (hereinafter abbreviated as "base material") have come to be used. As the frame material of the above-mentioned Cu-Zn-based and Cu-Sn-based alloys, those having an elongation of 5 to 50% have been used in order to prevent the occurrence of cracks during bending. More specifically, for example, a strip of Cu-30% Zn-based alloy is subjected to Cu undercoating with a thickness of 1 μm and then a thickness of 5
It is used as a frame that has been plated with 7 to 7 μm of bright solder. This bright plating is used to improve the solderability of the base material. Also,
For example, a Cu-4% Sn-0.2% P alloy having a thickness of 2 to 5 .mu.m on which Ni undercoat is plated and then a bright solder plating having a thickness of 5 to 7 .mu.m on it is also used as a frame. .

[0004]

When resin-sealing is performed using these plated frames and the outer lead portions are bent by 90 ° in the final step, the bent corner portions of the metal base material are Fine cracks occur, and when soldering onto the substrate, these fine cracks cause deterioration of solder wettability due to aging in the bent portion,
Poor soldering occurs on board mounting.

When a Cu-Zn alloy is used for the frame, Zn is deposited and diffused in the solder plating layer during soldering,
Remarkably hinders solder wettability. Similarly, when the outer lead portion of a frame obtained by applying a solder bright plating to a Cu-Sn alloy is bent by 90 °, fine cracks are generated in the solder plating layer even if microcracks are not generated in the base material. Soldering failure occurs when the outer lead is joined to the lead of the external element during mounting on the board.

[0006] Such soldering failure in mounting on a substrate has become a serious problem in terms of reliability of the electroacoustic transducer. That is, when analyzing the cause of the electroacoustic transducer failure,
It was found that one of the causes was a connection defect because solder did not flow into the cracked part during mounting.

[0007]

As a result of various studies in view of this, the present invention develops an electroacoustic transducer lead frame capable of producing an electroacoustic transducer with high reliability while economically plating the frame. The growth rate is 20
In a frame molded from a metal board plate strip of more than%,
Ni base plating with a plating solution containing no brightening agent is applied to the entire surface of the frame or at least the lead terminal portion,
It is characterized in that a solder plating with a plating solution containing no brightening agent is applied thereon.

In the present invention, the Ni plating bath and the solder plating bath are each plated without containing a brightening agent made of an organic compound such as thiourea, saccharin, glucose or the like or an inorganic compound such as thiosulfate. This is because when the brightener is contained, the plated surface becomes glossy and the plated structure becomes finer, and cracks easily occur in the plated film when the frame is bent. The plating formed by the plating solution containing no brightening agent 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, but 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 rate of the strip alloy of the metal substrate is set to 20% or more in order that the metal base material having the elongation rate of less than 20% is subjected to press forming or etching and then plating, followed by bending. This is because when processing is performed, cracks are generated in the corners of the lead portion, the base plating is oxidized due to changes with time, and the wettability of the solder deteriorates.

That is, according to the present invention, a metal substrate sheet alloy having an elongation of 20% or more is formed into a frame by pressing or etching, and then the surface of the frame 1 has a thickness of 0.01 to 2. As shown in FIG. 0 μm, preferably 0.
A matte Ni undercoat having a thickness of 05 to less than 0.3 μm is applied, and a coating layer of a 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 plated by electroplating to a desired thickness and coated. 90% Sn-10% Pb-based solder is particularly preferable.

Fe-3 as the metal substrate in the present invention
5.5-36.5% Ni alloy, Fe-40.5-41.
F such as 5% Ni, Fe-49.5 to 51.5% Ni alloy
An e-Ni-based alloy and a copper alloy such as brass, phosphor bronze, and phosphor bronze for springs are preferably selected, but have an elongation rate of 20% or more, and are well compatible with Ni undercoat and have good solder wettability. If so, a metal substrate other than the above can be selected.

In order to increase the elongation rate of the Fe-Ni alloy to 20% or more, it is advisable to adopt a process in which the rolling rate (sheet thickness reduction rate) of the temper rolling after recrystallization annealing is 10% or less. The strain rate is further increased by performing stress relief annealing after temper rolling, but strain relief annealing at 500 to 600 ° C. is preferable in order to prevent a decrease in strength. In addition, after rolling, temper annealing is 600 to
An elongation of 20% or more can be obtained by carrying out at 700 ° C, but temper rolling has less variation in quality than temper annealing.

Copper-based alloys have a rolling ratio of 20% or less for temper rolling of recrystallization annealing, and 1 for general phosphor bronze.
5% or less, 25% or less for phosphor bronze for springs,
By rolling, an elongation rate of 20% or more can be obtained.

The frame of the present invention has the above-mentioned structure, and the elongation rate of the metal base material is set to 20% or more to prevent the occurrence of cracks during the 90 ° bending process of the lead terminal portion.
Further, by coating the surface of the lead terminal portion mounted on the substrate with Ni plating, diffusion of the contained component elements from the base material is prevented. Also, by making the Ni plating and solder plating coated on the base material dull, 90 °
Prevents the generation of fine cracks in the plated part due to bending.

However, the thickness of the matte plating of Ni is 0.
It is necessary to set the thickness to 01 to 2 μm, and if the coating thickness is less than 0.01 μm, the effect as a diffusion barrier for alloying elements and impurity elements contained in the metal substrate under the heating condition at the time of sealing the synthetic resin is lost, and If it exceeds, it is uneconomical because it does not have a greater effect. The thickness of the Ni coating layer is preferably 0.05 to 0.3 μm.

When the bright Ni plating is applied as in the conventional method, the electrodeposited nickel has a large amount of strain and becomes fine crystals, and as a result, it is harder and less workable than the metal base material, and therefore the outer lead portion of the lead terminal is bent. A crack is generated during processing, which leads to a defect in the lead portion. Particularly, in the electroacoustic transducer, the bending of the outer lead has a radius (r) of 0.5 mm or less and a plate thickness (t).
Since the ratio (r / t) to (2) is strict as 2.5 or less and excellent workability is required for the plating layer, dull Ni plating was used in the present invention.

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 board mounting 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 solder coating layer is matte plating is the same as in the case of Ni plating. Hereinafter, the present invention will be described in detail with reference to examples.

The preferred matte plating bath composition and conditions 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 ° C. to 55 ° C. Current density ^{: 1A / dm 2 ~8A / dm} 2 B. Matte solder plating bath composition Stannous borofluoride: 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 ° C. to 30 ° C. Current density: 1 A / dm ^{2 to} 6 A / dm ²

[0020]

Examples 0.2 m thick with 20% elongation in each case
Fe-36% Ni alloy, Fe-42% Ni alloy, F
e-50Ni% alloy, brass and phosphor bronze specified in JIS H 3110, and phosphor bronze for springs specified in JIS H 3130, metal base strip 10 mm wide and 100 mm long in the rolling direction.
mm strip-shaped test pieces, which are used in Example 1 of the present invention.
.About.6 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

Matte solder plating was performed by the following method. (1) Bath composition stannous borofluoride 80 g / L lead borofluoride 10 g / L free hydrofluoric 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 3 A / dm ²

Further, as a comparative example, the same kind of metal base material having an elongation rate of less than 20% was used as a comparative example, and the thickness of 0.
A strip-shaped test piece having a width of 2 mm, a width of 10 mm, and a length of 100 mm was prepared and subjected to an evaluation test.

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

Bright solder plating was performed by the following method. (1) Bath composition: stannous borofluoride 150 g / L lead borofluoride 50 g / L free hydrofluoric acid 100 g / L free boric acid 25 g / L β-naphthol 1 g / L formalin 20 g / L brightener (amine aldehyde-based ) 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 Fe Fe-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 spring phosphor bronze: 7.9% Sn, 0.20 P, the balance Cu

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

(2) Solderability of plating: A test piece obtained by applying a rosin / alcohol-based flux to a test piece obtained by subjecting a metal substrate to predetermined undercoating and solder plating is tested at 230 ° C.
The solder wetted area was observed by immersing the solder in 60% Sn-40% Pb solder held for 5 seconds.

(3) Solderability after heat resistance test: A test piece obtained by subjecting a metal substrate to predetermined undercoating and soldering is bent at 90 ° in the rolling parallel direction, and then at 150 ° C for 24 hours.
After heating in the atmosphere for a period of time, soldering was performed by the method described in (2) above. The test results are shown in Tables 1 and 2.

The evaluation of each characteristic was performed by the following methods. Plating adhesion: The test piece was bent at 90 ° and the presence or absence of plating peeling was determined. Solderability of plating: A solder wet area of 95% or more was passed, and less than 95% was rejected. Solderability after heat resistance test: Solder wet area 95% or more was passed, and less than 95% was rejected.

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

[0032]

As described above, according to the frame of the present invention, the high elongation of the metal base material and the characteristics of the solder plating can be effectively exhibited, and a highly reliable electroacoustic transducer can be manufactured. Is. Further, this frame is also expected to bring about a remarkable effect as a frame of an electronic component which requires a high elongation of a metal substrate and solder plating, and is subjected to severe bending work.

[Brief description of the drawings]

FIG. 1 is a chart (Table 1) showing a structure and characteristics of a lead of an example of the present invention.

FIG. 2 is a chart (Table 2) showing a 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 base material 3 dull Ni plating coating layer 4 dull solder plating coating layer 5 guide hole 6 lead terminal 7 outer lead part of lead terminal (external terminal)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Sone No. 20-10 Nakayoshida, Shizuoka City, Shizuoka Prefecture Star Precision Co., Ltd. In the company

Claims (6)

[Claims] 1. A thickness of 0.01 formed by a plating solution containing no brightening agent on a molded body of a metal substrate having an elongation of 20% or more.
To 2.0 μm Ni base plating layer and a thickness of 1 to 10 μm formed on it by a plating solution containing no brightening agent
A lead frame for an electroacoustic transducer, which has a solder plating layer of m. 2. A metal substrate selected from the group consisting of Fe-Ni alloys, brass, phosphor bronze and phosphor bronze for springs.
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 a Fe—Ni-based alloy that has been temper-rolled at a rolling rate of 10% or less after recrystallization annealing. 4. The lead frame for an electroacoustic transducer according to claim 1, wherein the metal substrate is brass that has been temper-rolled at a rolling rate of 20% or less after recrystallization annealing. 5. The general phosphor bronze, wherein the metal substrate is temper-rolled at a rolling rate of 15% or less after recrystallization annealing.
A lead frame for the electroacoustic transducer described. 6. The lead frame for an electroacoustic transducer according to claim 1, wherein the metal substrate is phosphor bronze for spring that is temper-rolled at a rolling rate of 25% or less after recrystallization annealing.