JP2000252611A - Wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the bonding strength between a plated layer and protective glass by specifying a surface roughness of a part of the plated layer which is covered by the protective glass. SOLUTION: A thick film resistor 6 is formed at a specified part of the surface of a plated layer 5 and of the surface of a multilayer substrate 1. Protective glass 7 is formed thick so as to cover the surface of the thick film resistor 6 and the plated layer 5 connected to the thick film resistor 6. The surface of the plated layer 5 is sandblasted to increase the surface roughness Rz of the plated layer 5. As for an abrasive to be sprayed by sandblasting, silicon carbide, glass, etc., is used. The particle size of the abrasive is preferably between #30 and #1000. The surface roughness Rz of the plated layer 5 after sandblasting is preferably 5 μm or above by an average surface roughness Rz of ten points specified in JIS B0601 to accomplish enough bonding strength between the plated layer 5 and the protective glass 7 deposited on the surface of the plated layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring substrate in which a plating layer formed on a surface electrode of a substrate is covered with a protective glass, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a wiring board (thick film circuit board) having a thick film used in a hybrid IC or the like, a laminated board is generally used in a circuit board having a large circuit scale or requiring high integration. . Among them, an alumina laminated substrate having a surface electrode portion plated with Cu is excellent in terms of manufacturing cost, formation of a thick film resistor, and solderability.

[0003] As such a wiring board, the present applicant has
An alumina laminated substrate in which a thick film resistor is formed on a substrate has been proposed (see JP-A-63-107087). In this alumina laminated substrate, tungsten (W)
Or a surface wiring layer made of molybdenum (Mo) and C
After sequentially forming the u-plated layers, a surface electrode section is formed by forming a Cu thick film conductor layer on the Cu-plated layer. Therefore, the connection between the surface wiring layer and the thick film resistor is made of Cu
It is performed through two layers, a plating layer and a Cu thick film conductor layer,
Among them, the Cu thick-film conductor layer is formed only for connection with the thick-film resistor, which is disadvantageous in cost.

Further, as a wiring board having another structure, a plating layer of Cu or the like is formed on a surface wiring layer made of W or Mo to form a surface electrode portion, and a thick film resistor is directly formed on the surface electrode portion. A connecting device is known (JP-A-56-14).
No. 6201). According to this configuration, since the thick-film resistor is formed directly on the plating layer, a Cu thick-film conductor layer is unnecessary, and the material used and the number of steps are reduced, which is advantageous in cost.

[0005]

In order to protect the thick-film resistor, it is necessary to cover the thick-film resistor with a protective glass (overcoat glass). In the configuration in which the film resistor is formed, there is a problem that the bonding strength between the protective glass and the plating layer is low, and as a result, the bonding strength between the protective glass and the substrate is low.

In view of the above, an object of the present invention is to improve the bonding strength between a plating layer and a protective glass in a wiring board in which a surface electrode portion having a plating layer is covered with a protective glass. I do.

[0007]

According to the present invention, the reason why the bonding strength between the plating layer and the protective glass is low is that the surface of the plating layer is flat and a sufficient bonding area can be obtained between the plating layer and the protective glass. This is because it has not been done. That is, the first aspect of the present invention is characterized in that a portion of the plating layer (5) covered with the protective glass (7) has a surface roughness (Rz) of 5 μm or more.

As described above, by increasing the surface roughness (Rz) of the plating layer (5), the bonding area of the surface of the plating layer (5) with the protective glass (7) can be sufficiently increased. It is possible to increase the bonding strength between the plating layer (5) and the protective glass (7). In addition, in this specification, the surface roughness (Rz) of the plating layer (5) means
It means a measured value of surface roughness based on a ten-point average roughness specified in JIS B0601.

According to the second aspect of the present invention, a substrate (1) having a surface wiring layer (4) formed on the outer surface is prepared, and a plating layer (5) is formed on the surface of the surface wiring layer (4). Then, the surface roughness (Rz) of at least a part of the surface of the plating layer (5) is set to 5 μm or more, and the portion of the plating layer (5) whose surface roughness (Rz) is increased in the plating layer roughening step is removed. It is characterized in that a protective glass (7) to be coated is formed.

[0010] Thereby, the bonding area of the surface of the plating layer (5) to be bonded to the protective glass (7) can be made sufficiently large, and the bonding strength between the plating layer (5) and the protective glass (7) can be reduced. A large wiring board can be manufactured. The surface roughness (R) of at least a part of the surface of the plating layer (5)
As a method of largely increasing z), there is a physical method or a chemical method. Specifically, as the physical method, sandblasting is performed on the surface of the plating layer (5) as in the invention of claim 3. More specifically, the abrasive sprayed onto the surface of the plating layer (5) by sandblasting has a particle size of # 3.
0 to # 1000.

Note that the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the substrate according to the present embodiment will be described with reference to FIG. The wiring substrate 100 has a laminated substrate 1 on which a plurality of ceramic substrates are laminated. The ceramic substrate is made of, for example, alumina, aluminum nitride, mullite, or the like. An internal wiring layer 3 is formed inside the multilayer substrate 1, and a surface wiring layer 4 electrically connected to the internal wiring layer 3 is formed on the outer surface of the multilayer substrate 1. These wiring layers 3 and 4 are made of a material mainly composed of a high melting point metal such as Mo or W.

The surface of the surface wiring layer 4 is made of C, which is a material having good bonding properties with solder and wire bonding properties.
Plating layer 5 made of u, Ni, Au, Ag, Al, etc.
It is covered with. The surface wiring layer 4 is a part to which a component (not shown) is soldered or wire-bonded via the plating layer 5, that is, a part mounting part.

A thick film resistor ₆ made of a LaB ₆ -based material or a SnO ₂ -based material is formed on predetermined portions of the surface of the plating layer 5 and the surface of the laminated substrate 1. The thick film resistor 6, the wiring layers 3, 4 and the plating layer 5 constitute a wiring part of the wiring board 100. Further, in order to improve the reliability and accuracy of the thick film resistor 6 on the surface of the laminated substrate 1, the thick film resistor 6 and the plating film 5 connected to the thick film resistor 6 are covered. A protective glass 7 is formed.

Hereinafter, a method of manufacturing the wiring board 100 having the above configuration will be described with reference to FIG. First, in a through hole forming step shown in FIG. 2A, a plurality of (three in this example) green sheets 1a mainly containing alumina particles are prepared, and the green sheets 1a are formed by punching or the like. A through hole 2 is formed. Next, FIG.
In the wiring printing process shown in FIG. 2B, a metal paste mainly composed of a conductor material made of a high melting point metal material such as W or Mo is filled in the through-hole portion 2 by a method such as printing or the like to form an internal wiring layer. Form 3 Further, the same metal paste as that filled in the through-hole portion 2 is printed on the surface of the green sheet 1a in a predetermined circuit wiring pattern to form the surface wiring layer 4.

Then, in a laminated substrate baking step shown in FIG. 2C, a plurality of green sheets 1a prepared in the above step are laminated, and the green sheets 1a are laminated in a reducing atmosphere (for example, a mixed atmosphere of H ₂ and N ₂ ). Alternatively, in a neutral atmosphere, for example, 1
By firing at a temperature of about 600 ° C., the laminated substrate section 1 is fired and formed. The substrate preparing step in the present invention includes the above-described through hole forming step, wiring printing step, and laminated substrate baking step.

Next, a plating layer 5 is formed on the surface wiring layer 4 in a plating layer forming step shown in FIG. In the present embodiment, Cu is used as the metal for plating in view of the formation of a thick-film resistor in a later process and the solder bonding property when connecting components. The plating method may be either an electrolytic plating method or an electroless plating method. The plating thickness is desirably, for example, 2 to 15 μm.

Next, in the plating layer roughening step shown in FIG. 2E, in order to increase the surface roughness Rz of the plating layer 5,
Sandblasting is performed on the surface of the plating layer 5. The portion where the sand blast is performed may be only the portion of the plating layer 5 where the protective glass 7 in the subsequent process is formed, but the sand blast is performed on other portions including the substrate ceramic portion where the plating layer 5 and the like are not formed. There is no problem. Alumina, silicon carbide, glass, or the like is used as an abrasive sprayed by sandblasting. The particle size of the abrasive is preferably from # 30 to # 1000 in order to obtain an appropriate surface roughness Rz of the plating layer 4. The surface roughness Rz of the plating layer 5 formed by sandblasting is JIS B060 in view of the bonding strength with the protective glass 7 formed on the surface of the plating layer 5.
It is preferable that the ten-point average roughness Rz specified in 1 be 5 μm or more.

Next, in a resistor forming step shown in FIG. 2F, a thick film resistor 6 is formed at a predetermined portion on the laminated substrate 1 so as to be in direct contact with the plating layer 5. The material of the thick-film resistor 6 is preferably a material that can be fired in a reducing atmosphere or a neutral atmosphere in order to prevent oxidation of W and Mo formed on the surface layer in the above-described wiring printing step. In consideration of the range and reliability, it is desirable to use a resistor paste containing a LaB ₆ -based material or a SnO ₂ -based material as a main component. This resistor paste is printed in a predetermined pattern by printing, dried, and fired at about 900 ° C. in a nitrogen atmosphere.

Next, in the protective glass forming step shown in FIG. 2 (g), the thick film resistor 6 is protected in order to protect the thick film resistor 6.
A protective glass (overcoat glass) 7 is formed so as to cover the plating layer 5 on which the thick film resistor 6 is formed (excluding the parts mounting portion and the terminals for inspection, etc.). As the material of the protective glass, it is preferable to use a material which can be fired in a reducing atmosphere or a neutral atmosphere and has a small variation in the resistance value of the thick film resistor 6, for example, zinc oxide or boron oxide as a main component. It is desirable to use a glass paste. After printing and drying this glass paste, it is fired at a temperature of 500 to 700 ° C. in a nitrogen atmosphere.

FIG. 3 shows the surface roughness Rz (μ
m) and the bonding strength between the plating layer 5 and the protective glass 7 (kgf / mm ² ). Five points with different surface roughness Rz (Rz1, Rz2, Rz3, Rz4,
Rz5), the bonding strength was measured. Joint strength is 8
The maximum value, the minimum value, and the average value of the measured times are shown, and specific numerical values are as shown in FIG.

3 and 4, it can be understood that the bonding strength between the plating layer 5 and the protective glass 7 increases as the surface roughness Rz of the plating layer 5 increases.
Further, the surface roughness Rz of the plating layer 5 shown in FIGS.
From the relationship between the surface roughness Rz and the bonding strength between the plating layer 5 and the protective glass 7, if the surface roughness Rz is 5 μm or more, a sufficient bonding strength between the plating layer 5 and the protective glass 7 can be obtained. I understand.

As described above, according to the present invention, a plating layer roughening step (FIG. 2 (e)) for increasing the surface roughness Rz of the plating layer 5 is performed in addition to the conventional wiring board manufacturing step. Only by this, it is possible to improve the bonding strength between the plating layer 5 and the protective glass 7. (Other Embodiments) In the above embodiment, in the plating layer forming step (FIG. 2D), C is used as the plating metal.
Although u was used, the present invention is not limited to this, and any of Ni, Au, Ag, and Al may be used.
By setting the surface roughness Rz to 5 μm or more in (e)),
As in the case of Cu, the bonding strength between the plating layer 5 and the protective glass 7 can be improved.

In the above embodiment, in the plating layer roughening step (FIG. 2E), the surface roughness Rz
Although sandblasting was performed on the surface of the plating layer 5 in order to increase the surface roughness, the present invention is not limited thereto, and the following method may be used. That is, the surface roughness of the plating layer 5 is polished by polishing the surface of the plating layer 5 using a polishing plate or the like in which the same abrasive used in the above sandblasting is attached to a plate material, cloth, paper, or the like. Rz can be increased.

In contrast to the above-mentioned physical methods such as sand blasting and polishing, a chemical method of immersing the wiring board 100 in a nitric acid or ammonium persulfate solution or the like for an appropriate time to chemically etch the surface of the plating layer 5 may be employed. In addition, the surface roughness Rz of the plating layer 5 can be increased. Further, the surface roughness Rz of the plating layer 5 can also be increased by increasing the surface roughness of the surface wiring layer 4 such as W serving as a base when the plating layer 5 is formed. As a method of increasing the surface roughness of the surface wiring layer 4, the surface wiring layer 4
To increase the particle size of W or the like that forms
There is a method of chemically etching the surface wiring layer 4 before formation.

In the above embodiment, the wiring board 100
Is a ceramic laminated substrate, but the present invention is not limited to this, and the present invention can be applied to a single-layer substrate as long as it has a configuration in which a protective glass is formed on the surface of a plating layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a wiring board according to an embodiment of the present invention.

FIG. 2 is a process chart showing a manufacturing process of the wiring board shown in FIG. 1;

FIG. 3 is a characteristic diagram showing a relationship between a surface roughness Rz of a plating layer and a bonding strength between the plating layer and the protective glass.

FIG. 4 is a table showing specific numerical values of surface roughness Rz and bonding strength in the characteristic diagram of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... laminated board, 2 ... through hole, 3 ... internal wiring layer, 4
... Surface wiring layer, 5 ... Plating layer, 6 ... Thick film resistor, 7 ... Protective glass.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Nagasaka 1-1-1 Showa-cho, Kariya-shi, Aichi F-Term in Denso Corporation (reference) 5E314 AA06 BB02 BB06 BB12 DD02 FF02 FF17 GG26 5E346 AA53 CC17 CC32 CC34 CC35 CC36 CC37 CC38 CC39 DD22 EE21 EE24 HH32 HH40

Claims (4)

[Claims] A substrate (1) having a surface wiring layer (4) formed on an outer surface thereof; a plating layer (5) formed on the surface of the surface wiring layer (4); and the plating layer (5). And a protective glass (7) formed so as to cover at least a part of the coating layer, wherein a surface roughness (Rz) of a portion of the plating layer (5) covered with the protective glass (7) is 5 μm or more. A wiring substrate, comprising: 2. A substrate preparing step for preparing a substrate (1) having a surface wiring layer (4) formed on an outer surface thereof; and a plating layer forming a plating layer (5) on a surface of the surface wiring layer (4). A forming step, a plating layer roughening step of making the surface roughness (Rz) of at least a part of the surface of the plating layer (5) 5 μm or more, and a plating layer roughening step of the plating layer (5). A protective glass forming step of forming a protective glass (7) that covers a portion having a surface roughness (Rz) of 5 μm or more. 3. The method according to claim 2, wherein the step of roughening the plating layer is a step of performing sandblasting on the surface of the plating layer (5). 4. In the sandblasting, the abrasive sprayed on the surface of the plating layer (5) has a particle size of # 30 to # 30.
4. The method for manufacturing a wiring board according to claim 3, wherein the number is # 1000.