KR100722072B1 - Connector terminal - Google Patents

Abstract

assignment

It is effective to prevent occurrence of a short circuit and increase in contact resistance in a portion to which mechanical compressive stress is applied, and to provide a connector terminal having excellent wettability of the alloy in a soldered portion.

Resolution

A connector having a plating layer structure having a mixed layer of a pure nickel layer, a nickel-tin intermetallic compound layer, a mixed layer composed of a nickel-tin intermetallic compound and pure tin, and a tin oxide layer on a base material in a portion to which mechanical compressive stress is applied. A connector terminal, wherein a part of the nickel-tin intermetallic compound in the mixed layer is in contact with the tin oxide layer.

Connector terminals

Description

Connector terminal {CONNECTOR TERMINAL}

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing of the plating layer structure which the part in which the mechanical compressive stress is provided in the connector terminal of this invention has.

2 is a schematic cross-sectional view for explaining a mechanism in which the connector terminal of the present invention prevents the occurrence of whiskers and the like.

3 is a schematic view of an example of a connector terminal of the present invention.

4 is a schematic cross-sectional view for explaining the use mode of the connector terminal of the present invention.

5 is a schematic cross-sectional view illustrating a mechanism in which a conventional connector terminal generates whiskers and the like.

(Explanation of symbols for the main parts of the drawing)

1: base material 2: nickel layer

3: Ni-Sn layer 4: mixed layer

5: tin oxide layer 6: nickel-tin intermetallic compound portion

7: pure tin part 8: plated layer structure (A)

9: mechanical compressive stress 10: connector terminal

11: part where mechanical compressive stress is applied

12: portion to be soldered 15: solder alloy

16 connector board 17 flexible board

18: slider 50: the base material

51 nickel layer 52 tin layer

53: nickel-tin intermetallic compound 54: tin oxide layer

55: mechanical compressive stress 56: whisker

57: extrusion part (or)

Technical field

The present invention relates to a connector terminal having a portion to which a mechanical compressive stress is applied for electrical connection with a terminal constituting the connector, in particular with another member such as a flexible substrate.

Background technology

Generally, the terminal which comprises a connector is plated on the whole surface. As the plating treatment, it is known to perform a reflow treatment after forming a tin layer on the nickel layer from the viewpoint of improving corrosion resistance and sliding performance (for example, Patent Document 1 and Patent Document 2).

However, in the conventional connector terminal obtained by the above-mentioned technique, whiskers generate | occur | produce, a problem arises that it contacts with the next connector terminal, and a short circuit arises. In addition, the wettability to the solder alloy of the connector terminal may be lowered, or the contact resistance of the terminal may be increased.

[Patent Document 1]

Japanese Patent Laid-Open No. 6-73593

[Patent Document 2]

Japanese Patent Laid-Open No. 20O1-59197

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and effectively prevents occurrence of short circuit and increase in contact resistance at a portion to which mechanical compressive stress is applied, and provides a connector terminal having excellent wettability to an alloy at a soldered portion. The purpose.

The present invention provides a plating layer structure having a mixed layer and a tin oxide layer sequentially formed of a pure nickel layer, a nickel-tin intermetallic compound layer, a nickel-tin intermetallic compound, and pure tin on a base material, wherein a mechanical compressive stress is provided. It is a connector terminal which is provided in the invention, and relates to the connector terminal in which a part of the nickel-tin intermetallic compound in a mixed layer is in contact with a tin oxide layer.

Although the detail of the mechanism of whisker generation in the conventional connector terminal is not clear, it is considered based on the following mechanism. As shown in FIG. 5, when the tin layer 52 is formed on the nickel layer 51 on the base material 50 and then reflowed, the nickel-tin metal is between the nickel layer 51 and the tin layer 52. The liver compound 53 is produced, and the tin oxide layer 54 is formed on the surface. At that time, if the treatment conditions are relatively weak and the reflow treatment is insufficient, there is a tin layer 52 containing no nickel-tin intermetallic compound. Since such a tin layer is easy to deform | transform, when a mechanical compressive stress 55 is given, internal stress will increase in the said tin layer. When the internal stress increases, the migration (transition) of tin atoms occurs, the crystal state of the tin layer formed during plating collapses, and the tin layer becomes unstable. Then, in the process of transition to a stable state, recrystallization advances, and it is considered that whisker 56 and the extrusion part (or 57) are formed as a result.

On the other hand, when the reflow treatment conditions are relatively strong, the formation of the nickel-tin intermetallic compound is promoted, and the tin layer is converted into the nickel-tin intermetallic compound layer, so that the solder wettability is lowered due to the nickel-tin intermetallic compound. It is considered that the contact resistance increases.

Best Mode for Carrying Out the Invention

The connector terminal of this invention has a plating layer structure (A) shown below in the part to which mechanical compressive stress is given.

As shown in Fig. 1, the plating layer structure (A) includes a nickel layer (2) made of pure nickel, a Ni-Sn layer (3) made of a nickel-tin intermetallic compound (6), and a base material (1). It has the mixed layer 4 and the tin oxide layer 5 which consist of the nickel-tin intermetallic compound 6 and pure tin 7 sequentially, and the nickel-tin intermetallic compound in the mixed layer 4 ( A part of 6) is in contact with the tin oxide layer 5. That is, the nickel-tin intermetallic compound (only Ni-Sn) produced between a pure nickel layer and a pure tin layer by forming a pure nickel layer and a pure tin layer sequentially, and then performing a reflow process suitably. Ni-Sn is grown until a part of the layer reaches the tin oxide layer. Therefore, the plating layer structure (A) does not have the tin layer which consists of pure tin which does not contain a nickel-tin intermetallic compound.

In this specification, pure tin is used to distinguish tin from the tin-tin intermetallic compound, and means tin (single) that does not constitute the intermetallic compound. In the present invention, pure tin is copper, magnesium, phosphorus It does not prevent containing impurity, such as these.

In addition, pure nickel is similarly used to mean nickel (single) which is used differently from nickel constituting the nickel-tin intermetallic compound and does not constitute the intermetallic compound. In the present invention, pure nickel is copper, magnesium, phosphorus It does not prevent containing impurity, such as these.

In the present invention, the portion where the mechanical compressive stress is applied in the connector terminal is the plating layer structure (A), so that whiskers or extruded parts (or) are generated over a long time even when the mechanical compressive stress is continuously applied and energized. To prevent. In detail, as shown in FIG. 2, even if mechanical compressive stress 9 is continuously applied to the plating structure (A) 8, it exists in the mixed layer 4, and also tin oxide layer 5 The nickel-tin intermetallic compound (6a) in contact with the s) is subjected to the stress and acts as a support column. Therefore, in the mixed layer 4, there is no increase in internal stress in the pure tin portion 7, and the pure tin portion 7 is not destabilized. As a result, recrystallization can be suppressed and generation | occurrence | production of a whisker and an extrusion part (or) can be prevented effectively.

The proportion of the nickel-tin intermetallic compound 6a in contact with the tin oxide layer 5 in the mixed layer 4 is such that whiskers or the like are supported by the nickel-tin intermetallic compound 6a supporting external stress. As long as the occurrence can be effectively prevented, it is not particularly limited. For example, the ratio of occupied area (Sn: Ni-Sn) of pure tin (Sn) and nickel-tin intermetallic compound (Ni-Sn) on the surface of the mixed layer after peeling the tin oxide layer 5 is 99: It is preferable that they are 1-20: 80, especially 8O: 20-50: 50.

Occupancy area ratio can be measured by the following method. However, it is not to be measured by the method described above, but may be measured by any method as long as the area ratio of Sn and Ni-Sn on the surface of the mixed layer can be measured.

The sample surface (surface of tin oxide layer) was repeatedly measured by Auger electron spectroscopy and argon ion etching (etching depth of about 1 nm), and the layer in contact with the tin oxide layer (the layer immediately below the tin oxide layer). To discover the appearance of The appearance of the layer in contact with the tin oxide layer can be seen by the distribution state in the depth direction of oxygen and the chemical shift state of the tin spectrum in Auger electron spectroscopy. Subsequently, the atomic ratio of Sn and Ni-Sn was calculated | required from the measurement data by Auger electron spectroscopy which noticed the appearance of the layer which contact | connects a tin oxide layer, and it was set as the occupancy area ratio of Sn and Ni-Sn.

In addition, the content of pure tin in the mixed layer 4 is preferably 20 to 80% by weight, particularly 40 to 60% by weight, from the viewpoint of more effectively preventing the occurrence of whiskers and the like and maintaining electrical characteristics. Do.

The content of pure tin can be measured by the following method. However, it does not have to be measured by the said method, and as long as the pure tin content of a mixed layer can be measured, it may be measured by what method.

The measurement by Auger electron spectroscopy and the argon ion etching (etching depth of about 1 nm) are repeatedly performed similarly to the measuring method of occupied area ratio, and the appearance of a mixed layer and the termination of a mixed layer are detected. The appearance of the mixed layer can be seen by the atomic ratio of tin and nickel in the layer in contact with the tin oxide layer. Since the atomic ratio of tin and nickel in the nickel-tin intermetallic compound is 3: 2, the presence of the mixed layer can be seen from the fact that the ratio of tin is higher than this atomic ratio and that nickel is present. The end of the mixed layer can be seen by the fact that the atomic ratio of tin and nickel reaches 3: 2. Next, content of pure tin is calculated | required as an average value by all the measurement data by Auger electron spectroscopy in a mixed layer.

The thickness of the nickel layer 2, the Ni-Sn layer 3, the mixed layer 4 and the tin oxide layer 5 is such that the surface of the mixed layer 4 has the above-mentioned area ratio (Sn: Ni-Sn). Although it does not restrict | limit especially, Usually, it is preferable to have thickness shown below from a viewpoint of whisker suppression and maintenance of favorable electrical characteristics.

Nickel layer; 1 to 5 μm, especially 2 to 3 μm;

Ni-Sn layer; 0.5 to 2 μm, especially 0.5 to 1 μm;

Mixed layer; 0.1 to 2 μm, especially 0.3 to 1.0 μm; And

Tin oxide layer; 0.001 to 0.05 μm, especially 0.001 to 0.015 μm.

As the formation method of the plating layer structure A as mentioned above, after forming a nickel layer and a tin layer on the base material 1 sequentially, an appropriate reflow process (heat-fusion process) is performed. If the reflow treatment conditions are relatively weak, there is a tin layer which does not contain the nickel-tin intermetallic compound as described above. That is, the nickel-tin intermetallic compound produced between the nickel layer and the tin layer does not grow enough to reach the tin oxide layer. Therefore, the nickel-tin intermetallic compound cannot act as a support column, and the tin layer becomes unstable due to internal stress, and as a result, a whisker and an extruded portion (or) are formed. On the other hand, if the reflow treatment conditions are relatively strong, the nickel-tin intermetallic compound is easily and excessively produced, and the interface with the tin oxide layer 5 in the mixed layer 4 is composed of only the nickel-tin intermetallic compound. And the contact resistance increases.

The method for forming the nickel layer is not particularly limited, and for example, nickel sulfate 30 to 380 g / l, nickel chloride 40 to 50 g / l, boric acid 45 to 50 g / l and additives (additives including anionic surfactants) 20 What is necessary is just to employ | adopt the bath composition of 40 ml / L, and the conditions of 40-55 degreeC, and 20-40 A / dm <2>. The nickel layer should just be formed so that thickness may be 1-4 micrometers normally, Preferably it is 2-3 micrometers.

The method of forming the tin layer is also not particularly limited, for example, acid 70 to 140 ml / l, tin 160 to 600 ml / l and additive (additive including nonionic surfactant) 20 to 80 ml / l The bath composition and conditions of 40-60 degreeC and 20-40 A / dm <2> may be employ | adopted. The tin layer should just be formed so that thickness may be 1-4 micrometers normally, Preferably it is 2-3 micrometers.

The reflow treatment is performed by heating and melting the formed nickel layer-tin layer. The heating method is not particularly limited as long as it can achieve a predetermined plating structure, and usually a warm air heating method is employed. The warm air heating method is a method of achieving heating by injecting warm air of a predetermined temperature at a predetermined pressure and time. According to the warm air heating method, it is easy to perform the reflow treatment only on the part to which the mechanical compressive stress is applied in the connector terminal, and furthermore, the processing conditions can be controlled relatively precisely, and the plating layer structure A is relatively easy. It is preferable because it can be formed. As another heating method, a furnace heating method for achieving heating by placing it in a furnace at a predetermined temperature for a predetermined time is known, but according to the method, a reflow treatment can be performed only at a portion to which mechanical compressive stress is applied in the connector terminal. Can not. Furthermore, since the processing conditions cannot be strictly controlled, it is very difficult to form the plating layer structure (A).

Reflow treatment conditions for forming the plated layer structure A depend on the thickness of the tin layer, the heating method, the shape of the connector terminal, the material, and the like, and thus cannot be defined in one word.

For example, when the thickness of a tin layer is about 2 micrometers and the warm air heating system of air volume 0.8m <3> / min is employ | adopted, hot air temperature is 340-440 degreeC, especially 380-400 degreeC, and processing time is 2-3 seconds. It is preferable to set it as.

For example, when the thickness of a tin layer is about 4 micrometers and the warm air heating system of air volume 0.8 m <3> / min is employ | adopted, it is preferable to make a warm air temperature 3800-400 degreeC and a processing time for 2-3 seconds. .

After performing the reflow process, a post-process is normally performed. What is necessary is just to achieve cooling of post-processing, for example, by natural cooling.

As a base material, any metal material conventionally used as a base material of a connector terminal can be used, For example, alloys, such as copper, copper, tin, iron, phosphorus, etc. are mentioned.

The base material is usually subjected to electrolytic degreasing treatment and acid activation treatment prior to the formation of the nickel layer.

The connector terminal of this invention also has another plating layer structure (B) in the part to be soldered. The plating layer structure (B) is not particularly limited as long as the surface has a pure tin layer. However, the plating layer structure (B) is formed on the base metal from the viewpoint of process simplification by simultaneous treatment with the portion having the plating layer structure (A) at the connector terminal. It is preferable to have a pure nickel layer and a pure tin layer sequentially. The base material is the same as described above.

Such a preferable plating layer structure (B) can be formed by the same method as the formation method of a plating layer structure (A) except not performing reflow process and post-process. The thickness of the nickel layer is usually 1 to 4 µm, particularly preferably 2 to 3 µm. The thickness of the tin layer is usually 1 to 4 µm, particularly preferably 2 to 3 µm.

The preferred solder alloy used when the connector terminal of the present invention is soldered to the connector substrate is Sn 3 Ag 0.5 Cu.

In the connector terminal of this invention, parts other than the part to which mechanical compressive stress is provided and the part to be soldered may have the plating layer of any structure, or may not have a plating layer. It is preferable to have only a pure nickel layer on a base material from a corrosion prevention viewpoint. The base material is the same as described above.

The nickel layer can be formed by the same method as the nickel layer at the time of forming a plating layer structure (A). The thickness of the nickel layer is usually 1 to 4 µm, particularly preferably 2 to 3 µm.

The connector terminal of this invention has a shape as shown in FIG. 3, for example. In the connector terminal 10 shown in FIG. 3, 11 is a part to which mechanical compressive stress is given, and has the said plated layer structure (A). In FIG. 3, 12 is a soldered part and has the said plating layer structure (B). In addition, from the viewpoint of facilitating the plating process and obtaining the effect of the present invention more reliably, the connector terminal 10 usually shows the entirety of the plated layer structure A as shown in FIG. The entire area is treated to have a plating layer structure (B).

The connector terminal 10 shown in FIG. 3 is used in the form as shown in FIG. 4, for example. Specifically, the connector terminal 10 is well secured to the connector substrate 16 by the solder alloy 15 at the portion 12 to be soldered. On the other hand, in the terminal 10, another member (for example, the flexible substrate 17, etc.) to which electrical connection with the terminal is to be achieved is inserted. Thereafter, the slider 18 is also inserted, and the mechanical stress is applied to the portion 11 through the flexible substrate 17 or the like, so that the electrical connection between the portion 11 and the flexible substrate 17 or the like is achieved. .

Example 1

The following process was performed sequentially about the copper base material (about 4 mm of full length (L of FIG. 3)) which has a shape as shown in FIG. 3, and the connector terminal was obtained.

(Electrolytic degreasing treatment)

The entire base material was immersed in an alkaline detergent having a concentration of 5% for 10 seconds and dried.

(Acid active treatment)

The entire electrolytic degreasing base material was immersed in an aqueous 5% sulfuric acid solution for 10 seconds and dried.

(Nickel plated)

Nickel plating was performed under the conditions of Table 1 on the entire surface of the acid-activated base material (nickel layer thickness; 2 µm).

(Tin plating treatment)

Both ends (in detail, X area | region and Y area | region of FIG. 3) of the nickel-plated base material were sequentially tin-plated on the conditions of Table 1 (tin layer thickness: 2 micrometers).

fair Bath composition Temperature Current density Nickel plating treatment Nickel sulfate; 300-380 g / l nickel chloride; 40-50 g / l boric acid; 45-50 g / L additive (additive including anionic surfactant); 20 ~ 40ml / ℓ   50 ℃ 34 A / dm ² Tin plating treatment mountain; 75 ml / l tin; 400 ml / l additive (additive including nonionic surfactant); 60ml / l   50 ℃ 31 A / dm ²

(Reflow processing)

The reflow process was performed on the X area | region (refer FIG. 3) of a tin-plated base material on the conditions of Table 2.

fair Example / Comparative Example Processing conditions   Reflow processing   Example 1 Warm air heating air volume; Temperature of 0.8 m ³ / min; 340-360 degreeC time; For 2-3 seconds

(After treatment)

The entire surface of the reflowed base material was immersed for 5 seconds in a water-soluble lubricant having a concentration of 10% and dried.

Examples 2 and 3, Comparative Examples 1 and 2

The connector terminal was obtained by the method similar to Example 1 except having changed the reflow process conditions into the conditions of Table 3.

fair Example / Comparative Example Processing conditions         Reflow processing Example 2 Warm air heating air volume; Temperature of 0.8 m ³ / min; 380-400 ° C. time; For 2-3 seconds Example 3 Warm air heating air volume; Temperature of 0.8 m ³ / min; 420 ~ 440 ° C time; For 2-3 seconds Comparative Example 1 Warm air heating air volume; Temperature of 0.8 m ³ / min; 300 to 320 ° C time; For 2-3 seconds Comparative Example 2 Warm air heating air volume; Temperature of 0.8 m ³ / min; 460-480 ° C time; For 2-3 seconds

Property evaluation

In the obtained connector terminal, the plating layer structure of X area | region (refer FIG. 3) was analyzed.

(Occupied area ratio)

The occupancy area ratio (Sn: Ni-Sn) in the surface obtained by peeling the tin oxide layer of the surface was measured.

(Net Tin Content)

The pure tin content in the layer immediately below the tin oxide layer on the surface was measured.

(Layer composition and thickness)

In addition, the layer structure and the thickness of each layer were measured (analytical conversion) by a scanning-type Auger electron spectrometer (made by Nippon Electronics Co., Ltd.). That is, the measurement by Auger electron spectroscopy and the argon ion etching (etching depth about 1 nm) were repeated, and the layer structure and thickness were investigated based on the measurement data. The layer structure and the thickness of each layer can be obtained by knowing the boundary of each layer based on the presence or absence of atoms intrinsic to each adjacent layer, and / or the ratio of the constituent atoms and the change thereof.

The results are summarized in Table 4.

Example / Comparative Example Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Occupied area ratio (%) (Sn: Ni-Sn) 85:15 65:35 23:77 100: 0 0: 100 Net Tin Content (weight &) 62 52 21 70 0 The layer just below the tin oxide layer Mixed layer Mixed layer Mixed layer Pure Sn layer Ni-Sn layer     Layer composition (thickness (㎛)) Tin Oxide Layer (0.005) Tin oxide layer (0.013) Tin oxide layer (0.009) Tin oxide layer (0.010) Tin oxide layer (0.013) Mixed Layer (0.26) Mixed Layer (0.46) Mixed Layer (0.12) Pure Sn layer (0.69) Ni-Sn Layer (1.5) Ni-Sn layer (0.71) Ni-Sn Layer (0.62) Ni-Sn Layer (1.45) Mixed Layer (0.51) Ni layer (2.1) Ni layer (1.9) Ni layer (2.1) Ni layer (2.2) Ni-Sn Layer (0.47) Base material Base material Base material Base material Ni layer (2.5) - - - - Base material - Whiskers ○ ○ ○ × ○ Contact resistance ○ ○ ○ ○ × Solder wettability ○ ○ ○ ○ ○

From these results, it turned out that it has a mixed layer in Examples 1-3.

In Comparative Example 1, it was found that a pure tin layer exists between the mixed layer and the tin oxide layer.

In Comparative Example 2, it was found that the mixed layer did not exist, and the Ni—Sn layer was present immediately below the tin oxide layer.

Function evaluation

(Short circuit at the part where mechanical compressive stress is applied)

Insert the FPC into the connector where the connector terminal is assembled, and after leaving for 50 hours at room temperature, check the whisker with an electron microscope. Evaluation criteria are shown below.

○; Whiskers total length was 0 μm (whiskers did not occur at all);

△; Whisker total length was 30 micrometers or less (practically no problem);

×; Whiskers total length exceeded 30 micrometers.

(Contact resistance of the part subjected to mechanical compressive stress)

Fit FPc to the connector which assembled the connector terminal, and measure it by a 4-terminal method with a circuit element measuring device. Evaluation criteria are shown below.

○; Contact resistance was 21 mΩ or less;

△; Contact resistance was 40 mΩ or less (practically no problem);

×; Contact resistance exceeded 40mΩ.

Mount the connector assembled with the 50 pin connector terminal on the printed board under the following conditions and check whether the fillet is formed. (Mounting conditions, solder type: Sn3Ag0.5Cu, mask thickness: 0.12, mounting temperature peak value 235 ℃.)

Both the Example and the comparative example had good wettability and could confirm the fillet shape on all the pins.

○; Check the fillet on every pin;

×; Unfilled fillet.

Since the connector terminal of this invention suppresses generation | occurrence | production of a whisker (beard) in the part to which mechanical compressive stress is applied, generation | occurrence | production of a short circuit can be effectively prevented. In addition, the contact resistance of the part to which mechanical compressive stress is applied is effectively reduced. Furthermore, the connector terminal of this invention is excellent in the wettability with respect to a solder alloy in the part to be soldered.

Claims (4)

A plating layer structure having a mixed layer consisting of a pure nickel layer, a nickel-tin intermetallic compound layer, a nickel-tin intermetallic compound, and pure tin and a tin oxide layer on a base material is provided in a portion to which mechanical compressive stress is applied. As a connector terminal, A portion of the nickel-tin intermetallic compound in the mixed layer is in contact with the tin oxide layer. The method of claim 1, The mixed layer surface at the interface between the mixed layer and the tin oxide layer has an occupying area ratio (Sn: NiSn) of pure tin (Sn) and nickel-tin intermetallic compound (Ni-Sn) of 99: 1 to 20:80. Connector terminal, characterized in that. The method according to claim 1 or 2, The content of pure tin in the mixed layer is 20 to 80% by weight, the connector terminal. The method according to claim 1 or 2, And said connector terminal has a plating layer structure having a pure tin layer as a plating layer structure separate from said plating layer structure at a portion to be soldered.

Images