JP4841135B2 - Conductive pad, sensor having conductive pad, and method of manufacturing conductive pad - Google Patents

Description

  The present invention relates to a conductive pad, a sensor having a conductive pad, and a method for manufacturing the conductive pad. More specifically, the present invention relates to a conductive pad having good conductivity and high adhesion strength to a lead wire, and a sensor having a conductive pad and a conductive layer. The present invention relates to a method for manufacturing a conductive pad.

  The joint structure between the conductive pad and the lead wire is an indispensable part for various electronic devices. A connection structure in which a lead wire is connected to a pad on a substrate on which a conductive pad is arranged is frequently used because it is easy to manufacture. On the other hand, in the case of small and precise electronic equipment, the performance of the connection structure is important. In particular, the strength of the connection structure between the conductive pad and the lead wire may cause disconnection or contact failure. It was a note on the above. There are welding, bonding, crimping, fitting, soldering, and the like as a method for connecting the conductive pad and the lead wire at the joint, and ultrasonic waves, lasers, or the like may be used for welding. Among them, as an easy and reliable method of connecting, a method of bonding a conductive pad and a lead wire with a conductive adhesive paste and sintering it at a high temperature to make a complete connection is known as an excellent method. This method is easy to automate the process, and is used for connecting a small and expensive platinum conductive pad and a platinum lead wire with a platinum paste. However, since the platinum paste is expensive, there has been a problem that a careful prior study for obtaining sufficient adhesive strength with a small amount of platinum paste is necessary. Therefore, Patent Document 1 proposes a method for connecting a conductive pad and a lead wire by sharing an adhesive paste and soldering. However, if the two methods are shared, the process must be complicated.

JP-A-7-130446

  The present invention provides a connection structure in which, when an end portion of a lead wire is connected to a conductive pad using an adhesive paste, the lead wire is peeled off due to poor adhesion between the lead wire and the conductive pad, or no conductive failure is caused due to poor connection. The purpose is to provide a conductive pad having a surface. Another object of the present invention is to provide a sensor having the conductive pad. Furthermore, an object of the present invention is to provide a suitable method for producing a conductive pad having the above connection structure.

The means of the present invention for solving the problems are as follows:
(1) A conductive pad having a connection portion to which a lead wire is connected , wherein the connection portion forms a multi-tiered terrace structure, and each terrace forming the terrace-like structure is formed of an adhesive paste. The upper terrace is a conductive pad formed directly only on the lower terrace .
(2) the terraces like structure is a conductive pad according to a structure without recesses on the lower part of the terraces at the boundary of the terrace of the lower and the upper terrace (1).
(3) The conductive pad according to (1) or (2), wherein the terrace structure is a two-stage structure.
(4) A sensor having the conductive pad according to any one of (1) to (3).
(5) The first adhesive paste is applied to the lead wire connection portion at least once and then heat-dried to form a lower terrace, and the second terrace is directly applied only on the surface of the lower terrace . preparation of an adhesive paste is applied to connect the lead wire end portions coated with the second adhesive paste, the conductive pad by firing the coated second adhesive paste after heating and drying to form a upper terrace Is the method.
(6) The method for producing a conductive pad according to (5), wherein the application of the first adhesive paste and the heat drying treatment are performed once.
(7) A method for manufacturing a sensor having a conductive pad manufactured by the method for manufacturing a conductive pad according to (5) or (6).

  The conductive pad of the present invention has high adhesive strength with the lead wire, and the lead wire is not peeled off from the conductive pad even if stress is applied to the lead wire. In particular, even in the case of a lead wire having hardness, even if a stress is applied to the lead wire in a direction perpendicular to the surface of the conductive pad, it does not easily peel off from the conductive pad. Since the adhesive paste is applied and baked and bonded, it has a good adhesiveness and is difficult to cause poor conductivity at the bonded portion. Such a conductive pad is excellent as a component of a small and precise electronic device such as a sensor. Furthermore, the manufacturing method of the conductive pad having the lead wire connection structure of the present invention can use the same apparatus as the lead wire bonding method using the conventional adhesive paste, and the conventional adhesive paste selection, heat drying conditions, and firing conditions. Thus, it is possible to provide a conductive pad with high strength with little need for trial and error of detailed bonding conditions in advance.

  The conductive pad of the present invention is a conductive pad in which a lead wire is bonded by forming an adhesive paste on the conductive pad in a stepped structure. Further, the terrace structure of the adhesive paste formed on the conductive pad is formed only on the adhesive paste surface in which the upper stage is the lower stage, and the conductive structure has a structure with no depression on the lower stage side at the boundary between the upper stage and the lower stage. It is preferable that it is a property pad. The multi-tiered terrace structure is, for example, a shape like a two-tiered mirror. The projected area from above is such that the upper mirror is smaller than the lower mirror and is placed on top of the lower one. However, the difference from the mirror is that the upper and lower stages are completely in close contact with each other, and a structure having no depression that falls or cuts at the boundary between the upper and lower stages is preferable. When there is no depression, when the boundary portion of this terrace structure is cut vertically, the line representing the surface of the terrace structure is expressed as the X direction in the horizontal direction and the Y axis direction in the vertical direction. The differential curve is in the zero or positive range. In particular, if there is a dent on the lower side of the boundary between the upper stage and the lower stage, it is not preferable because the lead wire easily peels off at this part. This depression includes a crack-like depression, and the crack is usually most likely to be peeled off. FIG. 1 shows an example of a sensor having a conductive pad of the present invention in which two lead wires are connected. FIG. 2 shows a state where one of the lead wire connecting portions is viewed from the lead wire side. The lower terrace adhesive paste 4 spreads thinly and adheres to the conductive pad to completely connect the conductive pad and the adhesive paste. Furthermore, the upper terrace adhesive paste 5 is bonded so as to rise on the lower adhesive paste 4. The adhesive paste 5 adheres the lead wire 3 so as to wrap around the end portion which is a connecting portion of the lead wire 3. The end portion of the lead wire refers not only to the most advanced cross-sectional portion of the lead wire, but also to the entire portion to be connected including the side surface of the tip portion. As a result, the first adhesive paste and the second adhesive paste are completely adhered, and the second adhesive paste and the lead wire are also firmly adhered. In other words, there is an upper adhesive paste hill that rises above the lower adhesive paste hill in the lower stage, and the lead wire protrudes from the upper hill. It can be said that such a lead wire bonding structure is the structure in which the lead wire and the conductive pad are most unlikely to peel off.

  Instead of the bonding structure shown in FIG. 2, the bonding structure of the lead wire as shown in FIG. 3 is also a good structure from the viewpoint of preventing the separation of the lead wire and the conductive pad. However, a large amount of adhesive paste is necessary and impractical, and should be avoided especially when using an expensive adhesive paste such as platinum paste. Also, there are adhesive structures as shown in FIGS. 4 and 5, both of which have a problem of usage because the conductive pads and lead wires are easily peeled off. It can be used if it has a multi-tiered terrace structure as shown in FIG. 6 or FIG. 7, but these have a dent near the upper stage on the lower terrace, and are peeled off compared to the structure of FIG. The strength drops. As described above, the conductive pad having the adhesive structure of the present invention is particularly effective when the lead wire is a relatively hard platinum wire or the like and the adhesive paste is expensive. This is because the maximum adhesive effect can be increased with a small amount of adhesive paste.

  As an example of use of a conductive pad using expensive platinum, there is a sensor as shown in FIG. Sensors are often used with platinum pads and lead wires because they are integrated with electrodes, have high sensitivity and stability, and are not easily affected by the usage environment. Even in such a case, the conductive pad of the present invention having an adhesive terminal in which the lead wire is securely bonded with a small amount of bonding platinum paste can be used effectively.

  Usually, the conductive pad connection structure of the present invention has a conductive pad, lead wire, and adhesive paste on the substrate, but any material may be selected according to the application. . The conductive pad substrate is made of a ceramic material in consideration of firing temperature and insulation. The conductive pads, lead wires, and adhesive pastes are often made of copper, gold, silver, platinum or the like. In particular, the effect of the present invention is great when an expensive material such as platinum is used.

  Since the connecting portion of the lead wire is important for the conductive pad of the present invention, a preferred method for manufacturing the conductive pad of the present invention will be described focusing on the manufacturing method of the lead wire connecting structure. First, the first adhesive paste is applied to the lead wire connection portion on the conductive pad disposed on the substrate and the vicinity thereof, usually once, or more than once in some cases, and heat-dried. Industrially, the first adhesive paste may be applied widely using a dispenser so that the first adhesive paste spreads thinly after heat drying. Also, the viscosity of the first adhesive paste should not be so high. If the viscosity is too high, coating may not be performed satisfactorily from the outlet of the dispenser. In addition, there is a drawback that it is difficult to be thinly spread after the heat drying treatment. The viscosity range is 120 to 300 Pa seconds, preferably 150 to 250 Pa seconds.

  As shown in FIG. 8, the second adhesive paste is applied in a dumpling form with a dispenser or the like on the adhesive paste heat-dried on the conductive pad in this manner. The second adhesive paste may be the same as the first adhesive paste or may be changed. An adhesive paste having a relatively high viscosity is easy to use within a range that does not impede workability with a dispenser or the like. If the viscosity is too low, when a lead wire described later is bonded and heat-dried, the adhesive paste flows downward, so that the lead wire is not put together and is in a state close to FIG. The viscosity range is 150 to 500 Pa seconds, preferably 200 to 300 Pa seconds.

  It is preferable that the end portion of the lead wire is inserted and connected to the dumpling adhesive paste so as to be attached to the second adhesive paste. Alternatively, the end portion of the lead wire may be placed on the first adhesive paste that has been heat-dried first, and then the second adhesive paste may be applied from above. The conductive pad to which the lead wire is attached is heated and dried and then fired, whereby the lead wire is completely connected to the conductive pad, the lead wire connection structure is completed, and the conductive pad of the present invention is manufactured. .

  The first and second adhesive pastes may be any conventional adhesive paste for connection. What is necessary is just to choose according to the material and use of an adherend, such as copper paste, silver paste, and platinum paste. Depending on the type of adhesive paste, conditions such as heat drying treatment and baking treatment are different, but if it is a commercial product, it may be treated according to product specifications. Usually, the heat drying treatment may be about 5 to 30 minutes at around 100 ° C. The firing conditions may be 800-1500 ° C. for about 10-30 minutes. The amount ratio of the first adhesive paste and the second adhesive paste is not particularly limited, but is usually 1 to 0.1 to 10, preferably about 1 to 0.2 to 5.

  In the manufacturing method of the conductive pad, it is preferable to attach the second adhesive paste so that the end portions of the lead wires are sufficiently attached, that is, wrapped, as shown in FIG. This state is particularly important in the state of the product after the heat drying treatment and baking treatment are completed. Moreover, it is preferable to prevent a dent such as a crack from occurring near the boundary between the upper and lower adhesive pastes when the product becomes a product as shown in FIGS. In order to avoid such problems, it can be easily improved by adjusting the viscosity of the adhesive paste as described above. The viscosity of the adhesive paste may be adjusted by adjusting the additive for the adhesive paste. Using a conductive pad manufactured by such a manufacturing method is effective as a method for manufacturing the sensor of the present invention having a connection portion with excellent adhesiveness.

(Examples 1-9)
As shown in FIG. 1, a first bonding platinum paste (platinum paste TR7905 manufactured by Tanaka Kikinzoku Co., Ltd.) is applied to a connecting portion of a lead wire 3 of a sensor 10 having a platinum pad 2 on a ceramic substrate 1 by a dispenser. 0.25 mg was applied and heat-dried at 100 ° C. for 15 minutes on a hot plate. This was cooled to room temperature, and 0.2 mg of the second bonding platinum paste (Platinum paste TR7905 manufactured by Tanaka Kikinzoku Co., Ltd.) was applied on the first bonding platinum paste that had been heat-dried as shown in FIG. To do. At this time, the second bonding platinum paste is formed in a hemispherical or mirror-like shape. In FIG. 8, the first bonding platinum paste that has been heat-dried is represented by reference numeral 4, and the second bonding platinum paste is represented by reference numeral 5. Referring to FIG. 8, the end of the platinum lead wire 3 is inserted toward the vicinity of the center of the mirror-like adhesive paste 5, and the end to be the connection portion of the platinum lead 3 is formed into a mirror-like shape. The adhesive paste 5 is wrapped. This was heat-dried at 100 ° C. for 15 minutes on a hot plate, and further baked at 1300 ° C. for 15 minutes in a baking furnace to completely adhere the lead wire 3 to the platinum pad 2. In all the examples, an adhesive paste having a two-tiered terrace structure was formed.

  Here, the difference between Examples 1-9 is that the viscosity of the adhesive pastes 1 and 2 is changed. Table 1 shows the adhesive paste used in each example. In the table, A is a low viscosity adhesive paste having a viscosity of 175 Pa seconds, B is a medium viscosity adhesive paste having a viscosity of 235 Pa seconds, and C is a high viscosity adhesive paste having a viscosity of 400 Pa seconds. In addition, the viscosity adjustment of the platinum paste was performed using a commercially available diluent for adjusting viscosity (TMS-1: manufactured by Tanaka Kikinzoku Co., Ltd.).

  The workability at the time of creating the platinum pad having the terrace structure thus created and the connection state of the lead wire to the platinum pad were evaluated. Table 2 shows the evaluation results of workability at the time of preparing the platinum pad, and Table 3 shows the evaluation of the connection state of the lead wires. Ten samples of each example and the following comparative examples were made and evaluated. The tensile strength is the peel strength when the lead wire is pulled in a direction perpendicular to the plane of the platinum pad.

(Comparative Examples 1-3)
Without applying the first adhesive platinum paste and heating and drying in the above example, 0.45 mg of the second adhesive platinum paste was directly formed on the platinum pad into a shape that was hemispherically or mirror-shaped by a dispenser. The platinum lead wire 3 is inserted into this. After the step of inserting the platinum lead wire, the lead wire 3 was bonded to the platinum pad 2 in the same manner as in the above example. In all the comparative examples, the terrace structure was not formed. Similar to the Examples, the viscosity of the adhesive paste used in Table 1 is shown, Table 2 shows the evaluation results of workability, and Table 3 shows the evaluation results of the connection state of lead wires.

Relative evaluation of workability with a dispenser ○ Good workability △ Normal workability × Difficult workability The first adhesive paste is a low-viscosity one that spreads flatly after heat drying and is most easily applied with the second adhesive paste. there were.
The second adhesive paste having medium viscosity adheres to the first adhesive paste and the platinum lead wire so as to wrap the platinum lead wire after heat drying after the platinum lead wire is bonded. It was in good condition.
The high-viscosity paste had poor mouth-opening from the dispenser for application, and the workability was not good.

Appearance evaluation x Cracking or peeling is observed in all.
△ Some cracks or flaking can be seen to the extent that there is no problem in use.
○ There are no clear cracks or peeling, but there are some adhesive paste shapes that are distorted.
◎ Nothing is cracked or peeled off. The adhesive paste shape is also good.

  As can be seen from Tables 1 to 3 above, compared to the comparative example in which the strength and the appearance are both applied with the adhesive paste and not in the two-step terrace shape, the adhesive portion formed in the two-step terrace shape by applying the adhesive paste twice. Is clearly good both in tensile strength and appearance. Among these, it is best to use the first adhesive paste as a low-viscosity paste and the second adhesive paste as a medium-viscosity paste, including workability. In addition, if a paste having a medium viscosity or a low viscosity is used, good workability and product results can be obtained. Even if a high-viscosity paste is used, if the workability is not a problem, a product with no problem in peel strength can be obtained.

  The conductive pad of the present invention can be effectively used in various electronic devices, particularly precision devices such as sensors, as a durable and highly reliable connecting component. Further, the method for producing a conductive pad according to the present invention is simple and easy to automate, and can be used for producing a small and expensive platinum conductive pad and a conductive pad of a platinum lead wire.

FIG. 1 is a perspective view of an example of a sensor having a conductive pad according to the present invention. FIG. 2 is a view of an example of the lead wire bonding portion of the conductive pad of the present invention as seen from the lead wire side. FIG. 3 is a view of an example of a lead wire bonding portion of a conventional conductive pad as viewed from the lead wire side. FIG. 4 is a view of an example of a lead wire bonding portion of a conventional conductive pad as viewed from the lead wire side. FIG. 5 is a view of an example of a lead wire bonding portion of a conventional conductive pad as viewed from the lead wire side. FIG. 6 is a view of an example of a lead wire bonding portion of a conductive pad having a depression as seen from the lead wire side. FIG. 7 is a view of an example of a lead wire bonding portion of a conductive pad having a depression as seen from the lead wire side. FIG. 8 is an explanatory view showing the method of manufacturing the adhesive pad of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate of conductive pad 2 Conductive pad 3 Lead wire 4 Lower adhesive paste 5 Upper adhesive paste 6 Sensor electrode portion 10 Sensor 11 having conductive pad with lead wire of the present invention Upper and lower boundary of adhesive paste Lower dent in the section

Claims (7)

A conductive pad having a connection portion to which a lead wire is connected ,
The connecting portion has a terraced structure with a plurality of steps ,
Each terrace forming the terrace-like structure is formed by bonding paste, and, the upper part of the terraces conductive pad is directly formed only on terraces lower. The terrace-like structure, electric conduction pad according to claim 1 is a structure without recesses on the lower part of the terraces at the boundary of the terrace of the lower and the upper terrace. The conductive pad according to claim 1, wherein the terrace structure is a two-stage structure.   A sensor comprising the conductive pad according to claim 1. After applying the first adhesive paste at least once to the lead wire connection part, heat drying treatment to form the lower terrace,
Apply the second adhesive paste directly only on the surface of the lower terrace formed ,
Connect the lead wire end portions coated with the second adhesive paste,
A method for producing a conductive pad, wherein the applied second adhesive paste is baked after being heated and dried to form an upper terrace . The coating of the first adhesive paste method for manufacturing a conductive pad according to claim 5, each heat drying treatment once.   A method for manufacturing a sensor having a conductive pad manufactured by the method for manufacturing a conductive pad according to claim 5.

Images