JP2002246715A - Substrate, its producing method and connecting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate, in which an end face electrode provided on the outer side face of the substrate can be jointed to the electrode of other substrate through a lead free solder, without causing problems, e.g. conduction faults. SOLUTION: Since the edge part of an end face electrode 16 on the surface side of the substrate is covered with a protective conductor film 15' of a Cu conductor material, a part of the end face electrode 16 covered with a protective conductor film 15' remains together with the protective conductor film 15', even if the edge film is thin when the end face electrode 16 of a substrate 11' is soldered to the electrode 18 of other substrate 17 through a lead free solder 20, because the protective conductor film 15' is composed of a Cu conductor material which is not diffused easily into the lead-free solder 20. Consequently, the edge part of the end face electrode 16 on the surface side of the substrate is prevented from being cut subjected to edge cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate useful for bonding an end face electrode provided on an outer surface of a substrate to an electrode of another substrate by lead-free solder, a method of manufacturing the substrate, and a connection structure of the substrate.

[0002]

2. Description of the Related Art FIGS. 1A to 1F show a conventional method for manufacturing a substrate having an end face electrode.

When manufacturing a substrate having an end face electrode, first, a substrate 1 is prepared, and a required number of through holes 1a are formed in the substrate 1 as shown in FIG.

[0004] Next, as shown in FIG. 1 (B), a conductor paste is printed by a screen printing method from the periphery of the opening on the surface side of the through hole 1 a to the inner wall portion to form an upper conductor film 2. 2 is dried and fired.

Next, as shown in FIG. 1 (C), the same conductive paste as that of the upper conductive film 2 is printed from the peripheral portion of the opening on the back side of the through hole 1a to the inner wall portion by screen printing to conduct with the upper conductive film 2. The lower conductive film 3 to be formed is formed, and the lower conductive film 3 is dried and fired.

Next, as shown in FIG. 1D, the same conductor paste as that of the upper conductor film 2 is printed by a screen printing method from the periphery of the opening on the back surface side of the center hole of the lower conductor film 3 to the inner wall portion. A reinforcing conductor film 4 that is electrically connected to the film 3 is formed, and the reinforcing conductor film 4 is dried and fired.

Next, as shown in FIG. 1E, the substrate 1, the upper conductor film 2, the lower conductor film 3, and the reinforcing conductor film 4 are divided with the division line DL as a boundary. On the outer surface of the divided substrate 1 ', an end surface electrode 5 composed of the divided upper conductor film 2', lower conductor film 3 'and reinforcing conductor film 4' is formed as shown in FIG. 1 (F). .

[0008]

The substrate 1 'after the division is
After a desired electronic component (not shown) is mounted as shown in FIG. 2A, it is mounted on another substrate 6 such as a motherboard. The substrate 6 is provided with an electrode 7 corresponding to the back surface of the end surface electrode 5 of the substrate 1 ′, and the end surface electrode 5 of the substrate 1 ′ is joined to the electrode 7 of the substrate 6 by solder 8. When a eutectic solder containing lead such as a Sn-Pb alloy is used as the solder 8, no particular problem occurs in soldering.

[0009] However, as shown in FIG.
Lead-free solder (Pb-free solder) recently attracting attention
When the end face electrode 5 is made of an Ag-Pd conductor material, almost all of the Ag-Pd diffuses into the solder 9 due to the solder erosion phenomenon.
When made of a Pt conductor material, Ag-Pt diffuses into the solder 9 due to the solder erosion phenomenon, though the degree varies depending on the temperature at the time of soldering, and the end face electrode 5 disappears or is in a state close to disappearance. As a result, the edge portion on the substrate surface side where the film thickness becomes the thinnest in the end face electrode 5 occurs, causing problems such as poor conduction and the reliability is greatly reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for connecting a terminal electrode provided on an outer surface of a substrate to an electrode of another substrate by using lead-free solder. Substrates that do not cause problems such as
An object of the present invention is to provide a method of manufacturing a substrate and a connection structure of the substrate.

[0011]

According to a first aspect of the present invention, there is provided a substrate having at least one end surface electrode extending from a front surface of the substrate to a back surface of the substrate, wherein the end surface electrode comprises: A first conductive film made of an Ag-based conductive material provided from the substrate front surface to the substrate back surface, and a second conductive film made of a base metal-based conductive material provided on at least an outer surface of an edge portion of the first conductive film on the substrate surface side; And a conductive film.

According to a fourth aspect of the present invention, in the method of manufacturing a substrate having at least one end surface electrode from the front surface to the rear surface of the substrate on the outer surface, at least one through hole is formed in the substrate. Process and A
forming a first conductive film made of a g-based conductive material, forming a second conductive film made of a base metal-based conductive material on at least an outer surface of an edge portion of the first conductive film on the substrate surface side, Dividing the first conductor film and the second conductor film with a through hole as a boundary.

Further, in the substrate connection structure according to the present invention, the Ag is provided so as to extend from the front surface of the substrate to the back surface of the substrate.
At least one end face electrode composed of a first conductor film made of a base conductor material and a second conductor film made of a base metal-based conductor material provided on at least an outer surface of an edge portion on the substrate surface side of the first conductor film. A first substrate provided on an outer side surface; and a second substrate having an electrode corresponding to a back surface portion of the end surface electrode of the first substrate. The end surface electrode of the first substrate is connected to an electrode of the second substrate by lead-free solder. It is characterized by being joined.

According to the connection structure of the substrate according to the first aspect and the substrate according to the sixth aspect, the base metal-based conductive material is formed on at least the outer surface of the edge portion of the first conductive film constituting the end face electrode on the substrate surface side. Is provided, the base metal-based conductive material is difficult for the second conductive film to diffuse into the lead-free solder even when the end surface electrode of the substrate is soldered to the electrode of another substrate by lead-free solder. Therefore, the portion of the end face electrode covered with the second conductor film remains with the second conductor film even if the edge film thickness is small, thereby cutting off the edge at the edge portion of the end face electrode on the substrate surface side. Is prevented from occurring. Further, according to the method for manufacturing a substrate according to the fourth aspect, the substrate according to the first aspect can be manufactured accurately and stably.

The above and other objects, constitutional features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.

[0016]

3 (A) to 3 (G) show a method of manufacturing a substrate having end electrodes according to the present invention.

When manufacturing a substrate having an end surface electrode, first, a substrate 11 of 0.635 mm in thickness and 96% alumina is prepared, and a through hole having a diameter of 0.3 mm is formed in the substrate 11 as shown in FIG. The required number 11a is formed. For forming the through hole 11a in the substrate 11, a perforation technique such as laser beam irradiation or punching can be selectively used.

Next, as shown in FIG. 3 (B), from the periphery of the opening on the surface side of the through hole 11a to the inner wall portion, A
The upper conductor film 12 is formed by applying a g-Pt conductor paste, and the upper conductor film 12 is dried and fired.

More specifically, a 325-mesh stainless steel screen with a bias of 10 μm is arranged on the front side of the substrate 11, and the Ag-Pt conductor paste is applied to the through-hole 11a while sucking air through the through-hole 11a. Print around the opening on the front side. By the way,
The Ag-Pt conductor paste is a 850 ° C. firing type, and is prepared by homogeneously mixing a metal powder of an Ag-Pt component, a low-melting glass frit, an organic binder, and an organic solvent. A part of the printed Ag-Pt conductor paste is drawn into the through hole 11a by air suction and applied to the inner wall of the through hole 11a. Ag after application
The -Pt conductor paste is dried at 150 ° C for 20 minutes and fired at 850 ° C peak and in-out for 50 minutes. By the way, the upper conductive film 12 after firing
Has a thickness of about 10 μm.

Next, as shown in FIG. 3 (C), the same Ag-Pt conductor paste as that of the upper conductor film 12 is applied from the periphery of the opening on the back surface side of the through hole 11a to the inner wall portion to conduct with the upper conductor film 12. The lower conductor film 13 is formed, and the lower conductor film 13 is dried and fired.

More specifically, as in the case of forming the upper conductive film 12, a 325-mesh, bias-coated, 10 μm-emulsion-thick stainless steel screen is arranged on the back surface of the substrate 11 after being inverted. The Ag-Pt conductor paste is printed around the opening on the back surface side of the through hole 11a while performing air suction through the center hole and the through hole 11a. A part of the printed Ag-Pt conductive paste is drawn into the through-hole 11a by air suction, applied to the inner wall of the through-hole 11a, and is electrically connected to the inner wall of the upper conductive film 12. The Ag-Pt conductor paste after application is dried at 150 ° C. for 20 minutes and baked at 850 ° C. peak and in-out 50 minutes. Incidentally, the thickness of the lower conductor film 12 after firing is about 10 μm.

Next, as shown in FIG. 3D, the same Ag-Pt conductor paste as that of the upper conductor film 12 is applied from the periphery of the opening on the back surface side of the center hole of the lower conductor film 13 to the inner wall portion. A reinforcing conductive film which is electrically connected to the conductive film is formed, and the reinforcing conductive film is dried and fired.

More specifically, similarly to the formation of the conductive film 12, a 325-mesh, bias-coated, 10-μm-emulsion-thick stainless steel screen is disposed on the back side of the substrate 11 after being inverted, and the lower conductive film 13 is formed. The Ag-Pt conductive paste is printed on the lower conductive film 13 around the opening on the rear surface side while performing air suction through the center hole of the upper conductive film 12. A part of the printed Ag-Pt conductor paste is drawn into the center hole of the lower conductor film 13 by air suction and applied to the inner wall portion of the center hole of the lower conductor film 13. The Ag-Pt conductor paste after application is dried under the conditions of 150 ° C. for 20 minutes, and has a peak of 850 ° C. and an in-out of 50 m.
It is fired under the condition of “in”. Incidentally, the thickness of the reinforcing conductor film 14 after firing is about 10 μm.

Next, as shown in FIG. 3 (E), a Cu conductor paste is applied from the peripheral portion of the opening on the surface side of the center hole of the upper conductor film 12 to the inner wall portion to conduct with the upper conductor film 12 and the reinforcing conductor film 14. A protective conductor film 15 is formed, and the protective conductor film 15 is dried and fired.

More specifically, as in the case of the formation of the conductive film 12, a stainless screen having a size of 325 mesh, a bias, and an emulsion thickness of 10 μm is arranged on the surface of the substrate 11.
The Cu conductor paste is printed around the opening on the surface side of the upper conductor film 12 while performing suction through the central holes of the upper conductor film 12, the lower conductor film 13, and the reinforcing conductor film 14. Incidentally, the Cu conductor paste is a low-temperature firing type at 600 ° C., and includes a metal powder of a Cu component, a low melting glass frit,
It is prepared by homogeneously mixing an organic binder and an organic solvent. A part of the printed Cu conductor paste is drawn into the center hole of the upper conductor film 12 by air suction and applied to the inner wall portion of the upper conductor film 12 and the lower conductor film 13
And conductive with the inner wall portion of the reinforcing conductor film 14. C after application
The u conductor paste is dried at 120 ° C. for 20 minutes, and fired at 600 ° C. peak and in-out for 30 minutes. Since the Cu conductor paste used to form the protective conductor film 15 is of a low-temperature sintering type and has a small shrinkage ratio during sintering, a sufficient film thickness is secured at the edge portion of the protective conductor film 15 on the substrate surface side. it can. Incidentally, the thickness of the protective conductor film 15 after firing is about 10 μm.

Next, as shown in FIG.
The upper conductive film 12, the lower conductive film 13, the reinforcing conductive film 14, and the protective conductive film 15 are divided on the dividing line DL as a boundary.

More specifically, the substrate 12 is folded and divided along a dividing groove formed on the substrate 11 in advance so as to pass through the center of the through hole forming position, or the substrate 12 is rotated by a rotating blade or an irradiation laser. The above-described division is performed by cutting 12 along the division line DL.

The outer surface of the substrate 11 'after division is shown in FIG.
The upper conductor film 12 ', the lower conductor film 13', the reinforcing conductor film 14 'and the protection conductor film 15' divided as shown in FIG.
Is formed. As can be seen from the figure, the outer surface of the edge portion on the substrate surface side of the upper conductor film 12 'of the end face electrode 16 is covered with the protective conductor film 15'.

By the way, in the claims, "first
The “conductive film” is a conductive film portion composed of the upper conductive film 12, the lower conductive film 13, and the reinforcing conductive film 14 before the division, or the upper conductive film 12 ′, the lower conductive film 13 ′, and the reinforcing conductive film 14 after the division. 'Indicates the conductor film portion constituted by. In the claims, the “second conductor film” refers to the reinforcing conductor film 14 before division or the reinforcing conductor film 14 ′ after division.
Point to.

Desired electronic components (not shown) for forming a hybrid integrated circuit and the like are mounted on the divided substrate 11 ', and the end face electrodes 16 provided on the outer surface of the substrate 11' are connected to the hybrid integrated circuit. Used as external terminals. The board 11 'after mounting the electronic components is mounted on another board 17 such as a motherboard as shown in FIG. The substrate 17 is provided with an electrode 18 corresponding to the back surface of the end surface electrode 16 of the substrate 11 ′, and the end surface electrode 16 of the substrate 11 ′
To the electrode 18 of the substrate 17. The solder 1
When a lead-containing eutectic solder such as an Sn-Pb alloy is used as No. 9, no particular problem occurs in soldering as in the related art.

On the other hand, as shown in FIG.
When using a lead-free solder (Pb-free solder), for example, a lead-free solder composed of Sn as a main component and one or more of Ag, Cu, Sb, Bi, In, Zn, etc. added thereto Although the degree differs depending on the temperature at the time of soldering, the Ag− in the portion of the end face electrode 16 not covered with the protective conductor film 15 ′ to which the solder 20 adheres is used.
The Pt diffuses into the solder 20 due to the solder erosion phenomenon, and the portion disappears or is almost disappeared.
6 is made of a Cu conductor material that hardly diffuses into the lead-free solder 20, the portion of the end face electrode 16 that is covered with the protective conductor film 15 ′ has the edge. Even if the film thickness is small, it remains together with the protective conductor film 15 ', thereby preventing the edge electrode 16 from being cut off at the edge portion on the substrate surface side.

The protective conductor film 1 made of a Cu conductor material
5 ′ is not so good in solder wetting as compared with the Ag-based conductor film, so that the lead-free solder 20 does not wet up to the surface side of the substrate 11 ′. Even if there is an uncovered portion, the portion is not adversely affected by the lead-free solder 20.

Therefore, even when the end surface electrode 16 provided on the outer surface of the substrate 11 ′ is soldered to the electrode 18 of another substrate 17 by the lead-free solder 20, problems such as poor conduction are reliably avoided and reliability is ensured. Properties can be greatly improved.

Incidentally, a Pb-free-claim solder having a composition of 1% by weight Sn, 2% by weight Ag and 0.5% by weight Cu was printed on the electrode 18 of the substrate 17 with a metal mask having a thickness of 0.15 mm. The end face electrode 16 manufactured by the method described above and the A manufactured by the conventional method shown in FIG.
After each of the end face electrodes made of the g-Pd conductor material and the end face electrodes made of the Ag-Pt conductor material manufactured by the conventional method shown in FIG.
After performing reflow three times at a peak of 0 ° C., a reliability test (85 ° C. high-temperature load test, total number of tests = 9) was performed. As a result, in the case of an end face electrode made of an Ag-Pd conductor material manufactured by a conventional method, 5/9 occurrences of conduction failure
In the case of the end face electrode made of the Ag-Pt conductor material manufactured by the conventional method, the number of occurrences of conduction failure is 9/9, whereas in the case of the end face electrode 16 manufactured by the above method, the conduction failure is poor. When the number of occurrences was 0/9, very good results were obtained.

In the above description, the protection conductor film 15 is formed so as to cover substantially the entire surface portion of the upper conductor film 12 and a part of the inner wall portion in the manufacturing process.
As shown in FIGS. 5A and 5B, the area of the surface portion of the protective conductor film 15 is reduced so as to cover a part of the surface portion of the upper conductor film 12 near the center hole, or Even if the protective conductor film 15 is formed so as to cover only the outer surface of the edge portion of the film 12 on the substrate surface side, the same function and effect as described above can be obtained.

In the above description, the reinforcing conductor film 14 is formed so as to cover the back surface portion and the inner wall portion of the lower conductor film 12 in the manufacturing process.
4 is not always necessary.

Further, in the above description, the protection conductor film 15 is formed on the outer surface of the edge portion of the upper conductor film 12 on the substrate surface side in the manufacturing process. However, as shown in FIG. A protective conductive film 21 similar to the protective conductive film 15 is formed on the outer surface of the edge portion of the conductive film 14 on the back surface side of the substrate, or the lower conductive film 13 is formed as shown in FIG.
A protective conductor film 22 similar to the protective conductor film 15 is formed on the outer surface of the edge portion on the back surface side of the substrate, so that when the end face electrode is formed by the lead-free solder 20, the reinforcing conductor film 14 and the lower conductor film 13 on the substrate back side are formed. Can also be prevented from being cut off at the edge portion.

In the above description, the protective conductor films 15, 21 and 22 are formed from a Cu conductor material in the manufacturing process.
u, Ni, Zn, Pb, Fe, Sn, Al, Co, Cr
Even if the protective conductor films 15, 21 and 22 are formed of a conductor material using one or more base metals such as the above, or a conductor material using an alloy of the above-mentioned base metals, the same operation and effect as described above can be obtained. .

[0039]

As described in detail above, according to the present invention,
Even when the end surface electrode provided on the outer surface of the substrate is soldered to an electrode of another substrate by lead-free solder, problems such as poor conduction can be reliably avoided and reliability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional method for manufacturing a substrate having an end face electrode.

FIG. 2 is a view showing a state in which an end face electrode of a substrate manufactured by the manufacturing method shown in FIG. 1 is soldered to another substrate using eutectic solder, and an end face electrode of the same board using lead-free solder; Diagram showing soldering to another board

FIG. 3 is a diagram showing a method of manufacturing a substrate having end electrodes according to the present invention;

FIG. 4 is a view showing a state where an end surface electrode of a substrate manufactured by the manufacturing method shown in FIG. 3 is soldered to another substrate using eutectic solder, and an end surface electrode of the same substrate using lead-free solder; Diagram showing soldering to another board

FIG. 5 is a view showing a modification of the manufacturing method shown in FIG. 3;

FIG. 6 is a view showing another modification of the manufacturing method shown in FIG. 3;

[Explanation of symbols]

11, 11 ': substrate, 11a: through hole, 12, 1
2 ': Upper conductor film, 13, 13': Lower conductor film, 14,
14 ': reinforcing conductor film, 15, 15', 21, 22, ... protective conductor film, 16: end surface electrode, 17: substrate, 18: eutectic solder, 19: lead-free solder.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05K 3/40 H01L 23/12 LF term (Reference) 5E317 AA22 AA24 BB12 BB14 CC22 CD23 CD27 CD32 CD40 GG03 GG07 GG09 5E319 AA03 AB05 AC01 AC11 AC18 BB01 CC33 GG03 GG13 5E344 AA02 BB02 BB06 CC09 CC11 CC25 DD03 EE17 EE26

Claims (9)

[Claims] 1. A substrate having, on an outer surface thereof, at least one end surface electrode extending from the substrate front surface to the substrate back surface, wherein the end surface electrode is formed of a first conductive material made of an Ag-based conductor provided from the substrate front surface to the substrate back surface. A substrate comprising: a conductive film; and a second conductive film made of a base metal-based conductive material provided on at least an outer surface of an edge portion of the first conductive film on the substrate surface side. 2. The substrate according to claim 1, wherein the second conductive film is made of a Cu-based conductive material. 3. The substrate according to claim 1, wherein a portion of the end surface electrode other than a front surface portion and a back surface portion of the substrate is provided on an inner surface of a groove provided on an outer surface of the substrate. The substrate as described. 4. A method of manufacturing a substrate having at least one end surface electrode from a substrate surface to a substrate back surface on an outer surface, the method comprising: forming at least one through hole in the substrate; Forming a first conductor film made of an Ag-based conductor material so as to reach; and forming a second conductor film made of a base metal-based conductor material on at least an outer surface of an edge portion of the first conductor film on the substrate surface side; A step of dividing the substrate, the first conductive film and the second conductive film with a through hole as a boundary. 5. The method according to claim 4, wherein the second conductive film is made of a Cu-based conductive material. 6. A first conductor film made of an Ag-based conductor material provided from the substrate surface to the substrate back surface, and a base metal-based conductor provided on at least an outer surface of an edge portion of the first conductor film on the substrate surface side. A first substrate having at least one end electrode formed of a second conductor film made of a material on an outer surface; and a second substrate having an electrode corresponding to a back surface portion of the end electrode of the first substrate. An end face electrode of the first substrate is joined to an electrode of a second substrate by lead-free solder. 7. The substrate connection structure according to claim 6, wherein the second conductor film of the first substrate is made of a Cu-based conductor material. 8. The substrate according to claim 1, wherein a portion of the end surface electrode of the first substrate other than the substrate front surface portion and the substrate rear surface portion is provided on an inner surface of a groove provided on an outer surface of the substrate. The connection structure of a substrate according to 6 or 7. 9. The substrate according to claim 6, wherein the first substrate forms a hybrid integrated circuit with electronic components mounted on the first substrate. Connection structure.