JP2756223B2 - Substrate through electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a through electrode on a substrate of a magnetic sensor such as a magnetoresistive element and a substrate applicable to various electronic devices.

[0002]

2. Description of the Related Art For example, in a magnetoresistive element used as a magnetic sensor such as a magnetic encoder, if an electrode for connecting a magnetic detecting portion to an external circuit is formed on the front surface side of a substrate, that is, on a side on which a magnetic film is formed, the magnetoresistive element is formed. When disposing the element in opposition to the magnetic recording body, it is necessary to arrange the element so as to avoid the swelling of the electrode part, so that the distance between the magnetic film and the magnetic recording body becomes too large, or the electrode part is formed with the magnetic recording body. However, there is a problem that it is necessary to dispose it from the facing surface. Therefore, a through-hole is formed in the substrate so as to penetrate the front and back surfaces, and an electrode for conducting connection between the front and back surfaces is provided in the through-hole to form a double-sided substrate. Substrate through electrodes have been proposed.

As a double-sided board as described above, high heat resistance,
From the viewpoint of high strength and high thermal conductivity, there is known a substrate in which an inorganic material such as ceramic is used as a substrate, a through hole is provided in the substrate, and a conductor such as Ag or Cu is formed inside the through hole. The ceramic forms a through hole by a punch or the like in a state of a green sheet before firing. On the other hand, there is one using photosensitive glass as a substrate. The photosensitive glass has an advantage that a substrate having a through hole can be easily obtained by irradiating ultraviolet rays only to a portion where a through hole is to be formed, performing a heat treatment, and performing an etching process. Further, when heat treatment or the like is further performed, the material becomes crystallized vitreous, and has a property of improving heat resistance and strength. By forming a conductor in such a through-hole of the photosensitive glass substrate, it can be used as a double-sided substrate.

However, in such a double-sided board,
If the hole remains with the electrode formed in the through hole,
When the substrate is transported using the air suction chuck during the device assembling process, air escapes through the hole and the suction chuck cannot be used, or a protective film formed to impart moisture resistance to the device is used. It is necessary to form not only the surface of the substrate but also the inside of the hole, which makes the process complicated, or when forming a resist on the surface of the substrate, the liquid reaches the back side through the through hole and the back surface is stained. There is a problem.

Therefore, there is also known a technique capable of filling a through-hole formed in a substrate with a conductive material to close the through-hole, thereby eliminating the problem caused by the remaining hole. The invention described in Japanese Patent Application Laid-Open No. Hei 4-118979 filed by the present applicant is an example thereof. Although not yet known, as described in the specification and drawings of Japanese Patent Application No. 4-12417 filed by the present applicant, the inner surface of a through-hole formed through the substrate in the front-to-back direction is formed. There has also been proposed a through electrode for a substrate in which a conductive film is formed and an insulator is filled in the through hole.

When the substrate is made of ceramic, a through-hole is formed in a green sheet state containing a binder, and a conductor paste is embedded in the through-hole and baked at the same time. Since the shrinkage ratio of the sheet is close to 20%, it is difficult for the through-hole to follow the shrinkage ratio of the conductive paste to form a gap, and the conductor is reliably held in the through-hole.

[0007]

However, it is quite difficult to fill a through-hole in a substrate which has already been formed as a substrate and does not exhibit a large shrinkage behavior, such as a photosensitive glass substrate as described above, with a conductor. difficult. Because, in order to enhance the adhesion between the through hole of the substrate and the conductor, the conductor needs to contain a certain amount of binder, but if the binder is included, the shrinkage is large, and the peripheral surface of the through hole and This is because a gap is generated between the conductor and the other way around, when the binder is not added to the conductor so that no gap is generated between the peripheral surface of the through hole and the conductor, or the ratio is extremely small even if added. This is because adhesion between the peripheral surface of the through hole and the conductor is reduced, and the conductor may fall out of the through hole.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. A through hole is formed in a substrate so as to penetrate the substrate in a front-to-back direction. In the substrate provided with the above, there is provided a through electrode in which a gap is not formed between the through hole and the electrode, the adhesion between the through hole and the electrode is good, and the electrode is not likely to fall out of the through hole. The purpose is to:

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for forming a through hole in a substrate in a front-to-back direction.
In this through hole, a through electrode for conducting connection between the front and back surfaces is provided.
A substrate provided with an inorganic binder on the peripheral surface of the through hole.
A conductive layer to which the inorganic layer is added.
Characterized by being filled with a conductor layer that does not contain inders
You. The substrate may be a photosensitive glass.

[0010]

[Action] Inorganic binder (hereinafter referred to as "binder")
Is well adhered to the peripheral surface of the through hole of the substrate and the conductor layer containing no binder. The conductor layer containing no binder has a small shrinkage, and there is no gap between the peripheral surface of the through hole of the substrate and the conductor layer to which the binder is added.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a through electrode of a substrate according to the present invention. 1 and 2, a substrate 1 is made of, for example, a photosensitive glass substrate. A through hole 2 penetrating the substrate 1 in a front-to-back direction is formed by covering a mask plate, irradiating ultraviolet rays, performing heat treatment, and performing etching. Is formed. In the through-hole 2, a through-electrode for electrically connecting the front and back surfaces of the substrate 1 is formed. This through electrode includes a conductor layer 3 to which a binder is added and a conductor layer 4 not containing a binder. The conductor layer 3 to which the binder is added is provided on the peripheral surface of the through hole 2, and the conductor layer 4 containing no binder is filled and formed inside the conductor layer 3.

The method for forming the above conductor layers 3 and 4 is as follows.
There is a method of filling a through hole 2 having a predetermined size with a conductive paste and baking the conductive paste. According to this method, the conductor layer can be easily formed. However, the amount of the solvent in the ordinary conductor paste is large, and it shrinks during drying to produce a gap between the conductor paste and the peripheral wall of the through-hole. There is a problem in that the gap between the conductor layer and the conductor layer shrinks and the gap between the peripheral surface of the through hole and the conductor layer further increases.

Therefore, first, a conductor layer 3 is formed of a conductor to which a binder is added on the peripheral surface of the through hole 2 of the substrate 1 and, if necessary, is baked. Then, the binder is contained inside the conductor layer 3. The conductor which does not fill is filled and baked as necessary to form the conductor layer 4. The conductive paste for forming the conductive layer 3 may be a general conductive paste to which a binder is added.

On the other hand, the conductor paste for forming the conductor layer 4 has a solid content of 90% or more, suppresses shrinkage during drying as much as possible, and has an average particle size of 50 μm or more so that the bulk density is not reduced. Don't be too small. Further, binders usually added such as glass and oxides are not added because they promote shrinkage due to surface tension. It is desirable that the conductor of the conductor paste forming the conductor layer 4 be of the same material type as the conductor of the conductor paste forming the conductor layer 3.

According to the embodiment described above, since the conductor layer 3 formed on the peripheral surface of the through hole is made of a conductor to which a binder is added, the shrinkage is large, but the adhesion to the substrate 1 is good. . On the other hand, since the conductor layer 4 filled inside the conductor layer 3 is made of a conductor containing no binder, the substrate 1
Adhesion with the polymer is poor, but hardly shrinks. Therefore, the conductor layer 4 suppresses the contraction of the conductor layer 3, and a through electrode having no adhesion to the through hole 2 of the substrate 1 and having good adhesion to the side surface of the through hole 2 is obtained. be able to. In addition, if the conductors of the conductor paste forming the conductor layers 3 and 4 are made of the same material, there is an advantage that the adhesion between the conductor layers 3 and 4 is improved.

Although various methods for forming the through electrodes on the substrate according to the above-described embodiments are conceivable, a screen printing method can be used as an example. First, a screen printing mask plate 5 is placed on the substrate 1 as shown in FIG. At this time, positioning is performed so that a predetermined mesh portion of the mask plate 5 matches the through hole 2. Next, the squeegee 6 is moved on the mask plate 5 while sucking air from the back side of the substrate 1, and the conductive paste 7 on the mask plate 5 to which the binder is added is scraped off by the squeegee 6. At this time, the conductive paste 7 is sucked to the back surface side of the substrate 1 through the mesh portion of the mask plate 5, and the conductive paste 7 adheres to the peripheral surface of the through-hole 2 to form the conductive layer 3.

When the conductive layer 3 is formed by filling the conductive layer 3 thus formed with a conductive paste containing no binder, the air suction force can be used. That is, as shown in FIG. 4, a filter paper 8 is arranged on one side of the substrate 1 so as to cover the through hole 2, and the conductive paste containing no binder is applied to the conductive layer 3 while sucking air through the filter paper 8. And scrape it off with a squeegee. By doing so, the conductor layer 4 is formed inside the conductor layer 3. However, the conductor layer 4 may be held down from above to further increase the density of the conductor layer 4.

Next, another embodiment of the present invention will be described. The embodiment shown in FIG. 5 is different from the embodiment shown in FIG.
And the conductor layers 10 and 12 to which a binder is added are filled and formed on the front and back sides of the substrate 1 with the conductor layer 11 interposed therebetween. Also in this embodiment, the contraction of the conductor layers 10 and 12 is compensated for by the conductor layer 11 so that no gap is formed between the conductor layer 10 and the through hole 2 of the substrate 1 and the adhesion to the side surface of the through hole 2 is good. It is possible to obtain a simple through electrode. In addition, if the conductors of the conductor paste forming the conductor layers 10, 11, 12 are made of the same material, there is an advantage that the adhesion between the conductor layers 10, 11, 12 is also improved.

The following method is an example of the method for forming the through electrode shown in FIG. First, a conductive paste to which a binder has been added is printed and formed on one side of the substrate 1 by the above-described screen printing method or the like, and one end of the through hole 2 is closed. Next, a conductive paste containing no binder is pressed in from the opening side of the through hole 2 and filled. Next, a conductive paste obtained by adding a binder to the remaining portion of the through-hole 2 is printed and formed by the above-described screen printing method or the like, and the through-hole 2 is completely closed.

Alternatively, as another example of the method of forming the through electrodes shown in FIG. 5, there is a method shown in FIG. First, a jig 13 having a protrusion 14 having the same diameter as the inner diameter of the through hole 2 of the substrate 1 is set in a state where the protrusion 14 is fitted into the through hole 2 from one side of the substrate 1. 2 is filled with a conductive paste containing no binder from the open end side of the conductive layer 1
Form one. At this time, the conductor layer 1 is placed on the opening end side of the through hole 2.
The portion 15 where 1 is not formed is left. Next, jig 13
Is removed, and a conductive paste containing a binder is added to both surfaces of the conductive layer 11 by screen printing or other methods from the front and back of the substrate 1 to form the conductive layers 10 and 12.

When the conductor layer containing the binder and the conductor layer containing no binder are formed in the thickness direction of the substrate 1 as in the above-described embodiment, the conductor layer containing no binder is formed on one side of the conductor layer containing no binder. A conductor layer to which only a binder is added may be formed. FIG. 7 shows such an embodiment, in which only the conductor layer 10 to which the binder is added and the conductor layer 11 which does not contain the binder are formed to overlap. The surface of the conductor layer 11 and the surface of the conductor layer 10 are on the same plane as the front and back surfaces of the substrate 1. In FIG. 7, if the lower side of the substrate 1 is the surface, for example, a magnetic film 17 or the like reaching the surface of the conductor layer 11 is formed on the surface side of the substrate 1, and the entire surface of the substrate 1 including this magnetic film is formed as a protective film. 18 protected. A lead frame or the like for connection to an external circuit is connected to the surface of the conductor layer 11 on the back side of the substrate 1 by soldering or other appropriate means. Note that the surface of the conductor layer 11 does not necessarily need to be a flat surface, and may be a concave surface 16 as shown by a chain line in FIG.

Although the material of the substrate used in the present invention is not limited to a specific material, the photosensitive glass substrate is easy to form a through hole and has good surface roughness as described above. The use of a photosensitive glass substrate is recommended because there is no shrinkage behavior of the formed through-hole and the adhesive strength with the conductor is sufficient. However, other materials may be used. For example, an alumina substrate has a sintering temperature of 110.
Since it is 0 ° C., it cannot be fired simultaneously using a common conductor such as Ag or Cu. However, when firing the conductor after sintering the alumina substrate, Ag or Cu
A conductor having a low melting point and high electric conductivity, such as a conductor, can be used.

The through electrode of the substrate according to the present invention is not limited to a magnetic sensor such as a magnetoresistive element, but can be applied to substrates of various electronic devices.

[0024]

According to the present invention, the substrate penetrates in the front and back directions.
A through hole is formed, and the space between the front and back surfaces is
A through electrode provided with through electrodes,
Provide a conductor layer to which an inorganic binder is added on the peripheral surface of the through hole,
A conductor layer containing no inorganic binder is placed inside this conductor layer.
Due to the filling, the conductive layer containing no binder suppresses the shrinkage of the conductive layer to which the binder is added, so that no gap is formed between the conductive layer and the through-hole of the substrate, and the adhesion to the side surface of the through-hole. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a through electrode of a substrate according to the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a cross-sectional view illustrating an example of a manufacturing process of the through electrode according to the embodiment.

FIG. 4 is a cross-sectional view showing another example of the manufacturing process.

FIG. 5 is a sectional view showing another embodiment of the through electrode of the substrate according to the present invention.

FIG. 6 is a sectional view showing an example of the manufacturing process of the through electrode according to the embodiment.

FIG. 7 is a sectional view showing still another embodiment of the through electrode of the substrate according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Through-hole 3 Conductor layer with binder 4 Conductor layer without binder 10 Conductor layer with binder 11 Conductor layer without binder 12 Conductor layer with binder

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 1/11 H05K 3/40

Claims (2)

(57) [Claims] 1. A substrate comprising: a through-hole penetrating in a front-to-back direction in a substrate; and a through-electrode for electrically connecting the front and back surfaces in the through-hole.
A conductor layer to which a binder is added is provided.
A through-hole electrode of a substrate, characterized by being filled with a conductor layer containing no inorganic binder . 2. The method according to claim 1, wherein the substrate is a photosensitive glass.
The through electrode of the substrate according to claim 1.