JP2002252461A - Wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board having conductor layers brazed and soldered to a metallic member, such as a ball terminal a lid body, etc., having high adhesive strength and superior accuracy of dimension. SOLUTION: The conductor layers 3 are formed in sticking states on the surface of a first green sheet 1 composed of a first ceramic composition, and a coating layer 4 composed of the first ceramic composition is formed on at least a part of the circumference each of the conductor layers 3. Then other part of the coating layer 4 is formed on the surface of the area of the green sheet 1 not coated with the first ceramic composition. In addition, a second green sheet 5 composed of a second ceramic composition which is not baked at the baking temperature of the first ceramic composition is laminated upon at least the surface of the green sheet 1 on which the conductor layers 3 are formed. After the laminate is baked at a temperature at which the first ceramic composition is baked, but the second ceramic composition is not baked, the second green sheet 5 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a semiconductor device package having a semiconductor element mounted on an insulating substrate surface, hermetically sealing the semiconductor element with a lid, and having a connection terminal on the lower surface of the insulating substrate. The present invention relates to a wiring board suitable for a method and a method for manufacturing the same.

[0002]

2. Description of the Related Art High reliability is required for a semiconductor element housing package for mounting a semiconductor element or the like.
Conventionally, a hermetic package in which a ceramic insulating substrate such as alumina is sealed with a metal lid is used for such a package.

However, since alumina ceramics have a high dielectric constant and must use a tungsten or molybdenum material or the like having a high electric resistance as an internal wiring layer, they are required to be used in a communication field using a high frequency band which has recently been receiving attention. Qualities cannot always be satisfied.

[0004] In the communication field where high frequency bands are used and circuits are highly integrated, packages using low-temperature fired ceramics as an insulating substrate are receiving attention. Low temperature firing ceramics have firing temperature of 800-1
Since the temperature is as low as 050 ° C., a metallized wiring layer can be formed by co-firing with a low-resistance conductor such as copper or silver;
In addition, they have been widely used in the communication field due to their low dielectric constant.

[0005] Usually, a package using low-temperature fired ceramics as an insulating substrate is manufactured by the following method. For example, a green sheet is produced from a composition comprising glass and a ceramic filler, a through hole is formed in the green sheet, and a conductive paste is filled in the green sheet, and the conductive paste is printed on a predetermined surface of the sheet to form a conductive pattern. Then, these sheets are aligned and pressure-laminated. At this time,
On the green sheet located on the outermost surface, a recess is formed at the center of the upper surface to accommodate semiconductor elements,
A conductor pattern to be a ring-shaped conductor layer for joining a metal lid is formed on the sheet surface. Alternatively, a conductor pattern serving as a pad for bonding connection terminals such as ball terminals is formed on the lowermost green sheet. Then, the laminate is manufactured by simultaneous firing with the conductor layer.

After the semiconductor element is mounted on the center of the upper surface of the package, a metal cover is joined to the ring-shaped conductor layer with a brazing material, and further, connection terminals and the like are formed on the pad conductor layer on the lower surface of the package. The semiconductor device is manufactured by brazing.

[0007] However, the conductor layer formed on the low-temperature fired ceramic substrate as described above has a problem of low adhesive strength. When the conductor layer is bonded to a connection terminal or a metal lid, the connection terminal may come off or the cover may not come off. There is a problem that the airtightness of the body is impaired. As means for solving such a problem, it is known to provide a ceramic coating layer made of the same ceramic material as the insulating layer around the conductor layer to reinforce the conductor layer.
No. 353, for example.

On the other hand, recently, in a wiring board using low-temperature fired ceramics as an insulating substrate, in order to prevent a decrease in dimensional accuracy due to shrinkage of firing, a surface of a green sheet laminate made of a low-temperature fired ceramic composition is coated on a surface of a green sheet laminate. By laminating and pressing a constraining sheet made of a ceramic composition that does not sinter at a temperature, and by firing, by suppressing firing shrinkage of the green sheet laminate in the X-Y direction by the constraining sheet and shrinking in the Z direction, Japanese Patent Laid-Open No. 5-102666 discloses a manufacturing method for improving dimensional accuracy in the X-Y direction.
And JP-A-4-243978.

[0009]

However, in order to increase the adhesion strength of the conductor layer to the insulating substrate, a dimensional accuracy in the X-Y direction is required in producing a wiring board having a ceramic coating layer formed around the conductor layer. When the firing method in which the firing shrinkage is suppressed as described above is applied in order to increase the temperature, the following problem occurs.

That is, as shown in FIG. 6, a conductor layer 32 is formed on the surface of the ceramic green sheet 31 (a), and a coating layer 33 for reinforcement is provided around the conductor layer 32 (b). When the constraining sheet 34 is laminated on the surface and fired (c), and the constraining sheet 34 is removed (d), the conductor layer 3
It is necessary to remove the constraining sheet 34 until the surface 2 is exposed, but in this case, there is a problem that the coating layer 33 formed around the conductor layer 32 is peeled off by this removing operation.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and more specifically, a conductor layer having a high adhesive strength and being brazed to a metal member such as a connection terminal or a lid. It is another object of the present invention to provide a wiring board having excellent dimensional accuracy and a method for manufacturing the same.

[0012]

The present inventors have conducted various studies on the above-mentioned problems, and as a result, the method for manufacturing a wiring board of the present invention has the following advantages. B) forming a conductive layer on the surface of the first green sheet, and c) forming a green layer on the surface of the first green sheet.
Covering at least a part of the periphery of the conductor layer with the first ceramic composition; and d) forming a conductor layer further on a surface of the conductor layer which is not covered with the first ceramic composition. And e) forming a second ceramic composition comprising a second ceramic composition that is not sintered at a firing temperature of the first ceramic composition on at least a surface side of the first green sheet after the step d) on which the conductor layer is formed. 2) laminating the green sheets, and f) firing the laminated body after the step e) at a temperature at which the first ceramic composition is fired and the second ceramic composition is not fired, and g).
e) removing the second green sheet from the fired product after the step.

That is, according to the present invention, after a coating layer is formed around the conductor layer formed on the surface of the green sheet, the conductor layer is further applied to the exposed portion of the conductor layer that is not covered. By increasing the thickness of the exposed part of
Even when the constraining sheet, which is the second green sheet, is removed until the conductor layer is exposed, peeling of the covering layer can be prevented, and the periphery of the conductor layer by the covering layer can be reinforced.

Further, the wiring board manufactured as described above includes a conductor layer brazed to a metal member on the surface of the ceramic insulating substrate, and at least a part of the periphery of the conductor layer. A ceramic coating layer is formed on the
When the thickness of the exposed portion of the conductor layer is larger than that of the peripheral portion, the peripheral portion covered by the coating layer can be buried more deeply, so that the conductor layer can be more strongly reinforced.

In the above-mentioned wiring board, connection terminals such as ball terminals and lead terminals and metal members such as metal lids are brazed to the conductor layer, and the connection terminals are brazed. In this case, a covering layer is formed on the entire periphery of the conductor layer, and in the case of a lid, the conductor layer is formed in a ring shape, and the covering layer is formed on an inner edge and / or an outer edge of the ring-shaped conductor layer. It is desirable to form a plating layer on the surface of the conductor layer when the conductor layer is brought into brazing contact with the conductor layer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a process chart of an example of a method for manufacturing a wiring board according to the present invention.

According to the manufacturing method shown in FIG. 1, first, a predetermined low-temperature fired ceramic composition is mixed with an organic binder and a solvent to prepare a slurry, and the slurry is used to prepare a well-known doctor blade method, a rolling method, or the like. Into a sheet shape as shown in FIG.
A green sheet 1a of 500 μm is prepared. And
Laser or micro drill,
A through hole having a diameter of 80 to 200 μm is formed by punching or the like, and the inside thereof is filled with a conductive paste to form a via hole conductor 2.

The conductive paste is formed by mixing a metal component such as Cu, Ag, and the like, an organic binder such as an acrylic resin, and an organic solvent such as toluene, isopropyl alcohol, and acetone. The organic binder is 0.5 to 15.0 based on 100 parts by weight of the metal component.
Parts by weight, the organic solvent is a solid component and an organic binder 100
It is desirable to mix at a ratio of 5 to 100 parts by weight with respect to parts by weight. Note that a slight glass component or the like may be added to the conductor paste.

Next, as shown in FIG. 1B, a conductor layer 3 is formed on the surface of the green sheet 1a on which the via hole conductor 2 is formed, and one unit of the unit having the via hole conductor 2 and the conductor layer 3 is formed. The green sheet 1a can be formed.

The conductor layer 3 has a thickness after firing of 3 to 30 μm, especially 10 to 30 μm, in order to increase the bonding strength with the metal member.
It is desirable to print with a thickness of 20 μm.

The conductor layer 3 can be formed by a screen printing method using a conductor paste containing at least one metal powder selected from the group consisting of Cu, Ag, and Al. In the conductive paste, the deformation of the wiring board is prevented by improving the bonding strength at the interface between the conductive layer 3 and the ceramic insulating substrate, or by matching the sintering shrinkage and the speed of the conductive layer 3 with the green sheet 1a. Therefore, it is desirable to add 10% by weight or less of glass.
Also, the binder in the vehicle used for the paste includes
As in the case of the green sheet 1a, it is preferable to use the above-mentioned acrylic resin having excellent thermal decomposability in a nitrogen atmosphere.

As another method, particularly, the width of a circuit formed by the conductor layer 3 is 75 μm or less, particularly 50 μm or less, and the pitch between the conductor layers 3 is 150 μm or less, particularly 1 μm or less.
In order to make fine wiring of less than 00 μm, the purity is 99% by weight.
It is desirable that the metal foil is formed of a metal foil made of at least one kind of high-purity metal selected from the group consisting of Cu, Ag, Al, Au, Ni, Pt, and Pd. In this case, a metal foil is adhered to the surface of a transfer film made of a predetermined polymer material or the like and etched to form a circuit pattern, and then transferred to the surface of the green sheet 1a.

Next, as shown in FIG. 1 (c), a slurry made of the low-temperature fired ceramic composition constituting the green sheet 1a is applied around the conductor layer 3 formed on the surface of the green sheet 1a as the uppermost layer. The coating layer 4 is formed by coating. At this time, the thickness of the coating layer 4 is preferably 10 to 60 μm in order to effectively reinforce the periphery of the conductor layer 3.

Thereafter, as shown in FIG. 1D, a conductive paste is further applied to the exposed portion of the conductor layer 3 where the coating layer 4 is not formed, of the conductor layer 3 where the coating layer 4 is formed. I do.

Then, with respect to the green sheet 1a formed according to FIGS.
A plurality of green sheets 1 produced in the same manner as in (b)
The laminates b to 1c are laminated and pressed to form a laminate as shown in FIG. For laminating the green sheets 1a to 1c, a method of applying heat and pressure to the stacked green sheets 1 to perform thermocompression bonding, applying an adhesive made of an organic binder, a plasticizer, a solvent, or the like, between the sheets and performing thermocompression bonding Methods and the like can be adopted.

Next, a green sheet 1a to 1c having a size equal to or larger than that of the green sheets 1a to 1c is formed by a doctor blade method, a rolling method, or the like using a ceramic composition which is difficult to sinter at the firing temperature of the laminate of the green sheets 1a to 1c. Green sheet 5
(Hereinafter, simply referred to as a restraint sheet 5).

Then, as shown in FIG. 1 (f), the constraining sheet 5 is laminated under pressure on both sides or one side of the laminate of the green sheets 1a to 1c. The thickness of the constraining sheet 5 laminated on the laminate of the green sheets 1a to 1c increases the constraining force, facilitates the volatilization of the organic component, and takes into consideration the removability of the constraining sheet 5 after firing.
The thickness is preferably 10 to 200% with respect to the total thickness of the laminate of ~ 1c. Note that the thickness of the constraint sheet 5 refers to the thickness of the constraint sheet 5 laminated on one surface of the laminate.

Next, the laminate is heated in an oxidizing or weakly oxidizing atmosphere at 100 to 850 ° C., particularly 400 to 750 ° C. to decompose organic components in the green sheets 1a to 1c and the via-hole conductor paste. After the removal, a temperature at which the green sheets 1a to 1c can be sintered, for example, 800 to
Firing in an oxidizing or non-oxidizing atmosphere at 1100 ° C.,
The conductor layer 3 and the via hole conductor 2 are fired simultaneously with the green sheet. When a Cu conductor is used as the conductor layer 3, the conductor layer 3 is fired in a non-oxidizing atmosphere, and
When a g conductor is used, firing can be performed in an oxidizing atmosphere such as the air.

According to the firing, the green sheet 1a
1c, the shrinkage in firing in the X-Y direction is suppressed by the close contact of the restraining sheet 5 that is not sintered at this firing temperature, and the green sheets 1a to 1c are fired only in the thickness direction (Z direction). Shrink.

If the cooling rate after such firing is too fast, cracks occur due to the temperature difference and the thermal expansion difference between the ceramic insulating layer and the conductor layer 3 and the restraining sheet 5, so that the cooling rate is 400 ° C. / hr or less. During firing, a load of 50 Pa to 1 MPa may be applied by placing a weight on the upper surface of the laminate to prevent warpage.

Then, from the fired laminate, FIG.
As shown in FIG. 2, the constraining sheet 5 formed on the outermost surface of the laminated body of green sheets 1a to 1c after firing (hereinafter referred to as a ceramic insulating substrate 6) is subjected to ultrasonic cleaning, polishing, water jet, chemical blast, and sand blast. And wet blasting. At this time, by removing the uppermost conductive layer 3 of the ceramic insulating substrate 6 until the surface is exposed, a wiring substrate in which the periphery of the conductive layer 3 is embedded in the insulating substrate 6 can be formed.

As shown in FIG. 2, the conductor layer 3 from which the constraining sheet 5 has been removed has a central portion, that is, a portion exposed on the surface, and the thickness of the insulating substrate 6 around the conductor layer 3. The central portion of the conductor layer 3 is thicker when a connection terminal, a metal lid, and the like are joined to the conductor layer 3 as compared with the thickness of the portion embedded in the inside. The covering layer 4 existing on the periphery of the conductor layer 3
As a result, the reinforcement around the conductor layer 3 by the coating layer 4 can be made stronger.

A metal member such as a connection terminal or a metal cover is brazed to the conductor layer 3. In this case,
At least one of Ni, Co, Cr, Au and Cu plating layers is formed on the exposed surface of the conductor layer 3 by electrolytic or electroless plating to a thickness of 1 to 10 μm, particularly 2 to 7 μm. Desirably, a plating layer made of at least one kind selected from Ni, Co, Cr and Cu is formed, and a plating layer made of Au is provided as an outermost layer on the surface of the plating layer, so that the wettability with the brazing material is improved. , And the bonding strength with the metal member can be increased.

In the present invention, the ceramic composition for forming the insulating layer of the wiring board may be formed from a low-resistance conductor such as copper or silver and has a low dielectric constant. A low-temperature fired ceramic composition which can be sintered at a low temperature is suitably used. As such a low-temperature fired ceramic composition, for example, a mixture of a glass component and a ceramic filler component is used.

As the glass component used, at least
Also SiO_TwoContaining, Al_TwoO_Three, B_TwoO _Three, ZnO, Pb
O, alkaline earth metal oxide, alkali metal oxide
Containing at least one of the following,
For example, SiO_Two-B_TwoO_ThreeSystem, SiO_Two-B_TwoO_Three-Al_TwoO_Three−
MO type (where M is Ca, Sr, Mg, Ba or Zn
Borosilicate glass, alkali silicate glass, etc.
Ba-based glass, Pb-based glass, Bi-based glass, etc.
It is.

These glasses are also amorphous glasses by firing, and are also alkali metal silicate, quartz, cristobalite, cordierite, mullite, enstatite,
At least one crystal of anorthite, Celsian, spinel, garnite, diopside, ilmenite, willemite, dolomite, petalite or a substituted derivative thereof
Those that precipitate seeds are used.

Further, as the ceramic filler component,
SiO ₂ such as quartz and cristobalite, Al
_At least one selected from the group consisting of ₂ O ₃ , ZrO ₂ , mullite, forsterite, enstatite, spinel, and magnesia is preferably used.

The above-mentioned glass component and ceramic filler component are obtained by mixing 10 to 90% by volume, particularly 50 to 80% by volume, of the glass component and 10 to 90% by volume, particularly 20 to 50% by volume of the ceramic filler component. Is used.

As other low-temperature fired ceramic compositions, SiO ₂ , B ₂ O ₃ , Al ₂
A known low-temperature firing ceramic composition mixed with an alkaline earth metal oxide such as O ₃ , CaO, BaO, and MgO, and an alkali metal oxide such as Li ₂ O and Na ₂ O can also be used.

In the above-mentioned manufacturing method, the restraining sheet 5 is mainly composed of a non-sinterable ceramic material. In particular, an inorganic component containing 0.5 to 15% by weight of glass, an organic binder, a plasticizer, a solvent, etc. Is obtained by forming a slurry to which the powder is added into a sheet. As a non-sinterable ceramic material,
Specifically, it is composed of a ceramic composition that does not densify at a temperature of 1050 ° C. or less.
Al ₂ O ₃ , SiO ₂ ,
At least one selected from the group consisting of MgO, ZrO ₂ , BN, and TiO ₂ and / or a composite oxide thereof (Mg ₂
Powder such as SiO _{4 and} MgSiO ₃ ). Further, as the organic binder, plasticizer and solvent, the same as those blended in the green sheet, specifically, an acrylic binder, a plasticizer such as dibutyl phthalate, a solvent such as isopropyl alcohol, acetone, and toluene are preferably used. Can be used.

The glass component in the constraining sheet 5 is such that the glass softening point is lower than the firing temperature in order to enhance the removability of the organic component from the green sheet 1 and the adhesion between the ceramic green sheet 1 and the constraining sheet 5. It is preferable that the temperature is higher than the decomposition and volatilization temperature of the organic component in the restraint sheet 5, particularly about 450 to 1050 ° C.

The average thermal expansion coefficient difference between the ceramic insulating substrate 6 obtained by firing the green sheet 1 and the constraining sheet 5 at 40 to 400 ° C. (hereinafter simply referred to as the average thermal expansion coefficient difference) is 3 × 10 ^−6. / ° C. or lower, particularly 2 × 10 ⁻⁶ / ° C. or lower, whereby cracks or peeling occurring near the bonding surface of the constraining sheet 5 of the ceramic insulating substrate 6 during cooling after firing, or the glass ceramic insulating substrate 6 It is possible to prevent cracks generated inside. In order to reduce the firing shrinkage on the surface (main plane) of the ceramic insulating substrate 6, it is desirable that the thermal expansion coefficient of the restraint sheet 5 be equal to or less than the thermal expansion coefficient of the ceramic insulating substrate 6. It is desirable that the thermal expansion coefficient of the constraining sheet 5 be equal to or greater than the thermal expansion coefficient of the ceramic insulating substrate 6 in that the tensile stress caused by the thermal expansion difference does not remain. The coefficient of thermal expansion of the restraint sheet 5 can be easily adjusted by changing the type of the non-sinterable ceramic material and glass, the particle size of the powder, and the like.

Since the shrinkage during firing of the wiring board obtained by the above method is suppressed only in the thickness direction by the restraint sheet 5, the shrinkage in the plane of the laminate is reduced, for example, when the laminate has a rectangular shape. Indicates that the contraction rate of one side length is 0.
5% or less, and since the ceramic green sheet 1 is uniformly and securely bonded by the constraining sheet 5 over the entire surface,
Warpage or deformation due to partial peeling or the like can be prevented.

FIG. 3 is a schematic sectional view of a package for housing a semiconductor element as an example of a wiring board obtained by the above method. According to the semiconductor device housing package A of FIG. 3, the insulating substrate 10 is formed of a laminate in which a plurality of ceramic insulating layers having a thickness of 50 to 250 μm are laminated. A concave portion 10 a for accommodating the semiconductor element 11 is formed at the center of the surface of the ceramic insulating substrate 10, and the concave portion 10 a is hermetically sealed by a metal lid 12. The metal lid 12 is joined to the ring-shaped conductor layer 13 formed around the concave portion 10a of the insulating substrate 10 where the semiconductor element 11 is mounted.

A wiring conductor layer 14 that is electrically connected to the semiconductor element 11 is formed on the surface of the insulating substrate 10 in the concave portion 10a.
5 and the like. Further, on the back surface of the insulating substrate 10, a plurality of connection pad conductor layers 17 electrically connected via the wiring conductor layer 14 and the via-hole conductor 16 formed inside the insulating substrate 10 are formed.
Connection terminals such as ball terminals 18 for connecting the package A to an external electric circuit board (not shown) are soldered to the connection pad conductor layer 17.

In such a structure, the ring-shaped conductor layer 1
3. The connection pads 17 are formed by co-firing with the ceramic insulating substrate 10;
When firing at a temperature of 50 ° C., the ring-shaped conductor layer 13 and the connection pad conductor layer 17 are desirably made of a conductor material mainly composed of copper or silver, which is a low-resistance conductor.

It is desirable that the metal lid 12 has a thermal expansion coefficient close to that of the insulating substrate 10, and in particular, it has a thermal expansion coefficient of 40.
It is desirable that the difference in thermal expansion coefficient at -400 ° C is 2 ppm / ° C or less. This means that the difference in thermal expansion coefficient is 2 ppm
If the temperature is higher than / ° C, a large stress is likely to be generated at the joint between the metal lid 12 and the ring-shaped conductor layer 13 due to a difference in thermal expansion with the insulating substrate 10, and the hermetic sealing performance of the metal lid 12 is high. This is because reliability may be impaired. From this viewpoint, it is particularly desirable that the metal lid 12 be made of a metal containing Fe, such as a 42 alloy.

In such a configuration, the thermal expansion coefficient of the metal lid 12 made of 42 alloy or the like is approximately 7 ppm / ° C., which is relatively close to that of general low-temperature fired ceramics constituting an insulating substrate. Even if the difference is small, a large stress due to a difference in thermal expansion occurs when the size of the lid is large.

According to the package A of the present invention, as shown in FIG. 4, the inner edge and / or the outer edge of the ring-shaped conductor layer 13 formed on the surface of the insulating substrate 10 are covered with the covering layer 19 having a predetermined width. By embedding in the inside 10, the bonding strength of the ring-shaped conductor layer 13 to the insulating substrate 10 can be increased, so that the airtight reliability of the package with the metal lid 12 can be improved.

As shown in FIG. 5, by embedding a predetermined width from the periphery of the connection pad conductor layer 17 formed on the back surface of the insulating substrate 1 into the insulating substrate 10 with the covering layer 19, the connection pad As a result, the bonding strength of the connection terminal 18 brazed to the connection pad conductive layer 17 can be increased.

The portions of the ring-shaped conductor layer 13 and the connection pad conductor layer 17 that are not embedded in the insulating substrate 10, ie, the exposed portions, are Ni, Co,
A plating layer 20 made of at least one of Cr, Au and Cu is formed, and a metal lid 12 and connection terminals 18 are joined to the plating layer 20 by a brazing material 21 such as solder. .

In order to sufficiently exert the effect of the covering layer 19, the embedded width L of the conductor layers 13 and 17 in the insulating substrate 10 is set at 20 mm from the inner edge and / or the outer edge.
It is desirably at least 100 μm, especially at least 100 μm.

According to the present invention, since the thickness t ₁ at the center of the conductor layers 13 and 17 is formed to be greater than the thickness t ₂ at the periphery, the depth x at the buried portion is reduced. In order to increase the size, the covering layer 1 of the conductor layers 13 and 17
9, the reinforcing effect on the conductor layers 13, 17 can be further exhibited. These conductor layers 13 and 17
The average thickness ((minimum thickness + maximum thickness) / 2) of the coating layer 19 in the non-exposed portion is desirably 10 to 70 μm.

The width M of the exposed portion of the ring-shaped conductor layer 13 that is brazed to the metal lid 12 on the insulating substrate 10
When the width is larger than 5 mm, the stress due to the difference in thermal expansion with the insulating substrate 10 increases, and when the width M of the exposed portion is smaller than 1 mm, the adhesive strength of the metallized layer itself to the insulating substrate decreases. Width M at exposed portion of ring-shaped conductor layer 13
Is preferably 1 to 5 mm, particularly preferably 1 to 3 mm.

Further, the plating layer 10 formed on the exposed surfaces of the conductor layers 13 and 17 is made of Au-S
Improves wettability with n-alloy and the like, brazing material 21 and conductor layer 1
3 and 17 and at the same time increase the strength of the conductor layers 13 and 1
7 to prevent the bonding strength of the metal member from being reduced due to the reaction between the metal member 7 and the brazing material 21.
m, the effect of preventing the above reaction is small. Conversely, if the thickness of the plating layer 20 is greater than 10 μm,
A high stress is generated between the conductive layers 13 and 17 at the time of formation, and cracks are generated by this stress, thereby impairing the airtight reliability and the like. Therefore, it is desirable that the thickness of the plating layer 20 be 1 to 10 μm, particularly 2 to 8 μm.

[0056]

EXAMPLES (a) As a low-temperature fired ceramic composition, SiO ₂ -A was used.
_{l 2 O 3 -B 2 O 3} -CaO-BaO based glass 50 parts by weight, the mixture of SiO ₂ a composition of 50 parts by weight 100
With respect to the weight parts, 12 parts by weight of an acrylic binder, 5 parts by weight of dibutyl phthalate, and 30 parts by weight of toluene were added to form a slurry. This slurry was formed into a green sheet having a thickness of 250 μm by a doctor blade method. Then, a through-hole was formed in the green sheet, and a conductive paste containing copper as a main component was filled to form a via-hole conductor. (B) Further, a conductor layer pattern for an electrode pad having a diameter of 1 mm for brazing ball terminals to the solder was formed on the conductor paste by screen printing so as to have a fired thickness of 10 μm. (C) Further, 150 μm around the electrode pad conductor layer
Was coated with the above slurry so that the thickness after firing was 20 μm. (D) Thereafter, the above-mentioned conductor paste was further applied to an exposed portion of the conductor layer for an electrode pad with a thickness of 10 μm. (E) Five green sheets provided with the conductor layers were laminated and pressed together with the green sheets on which the conductor layers for electrode pads were formed as described above. (F) On the other hand, as a binding sheet, SiO ₂ -Al 5 parts by weight of the SiO ₂ 100 parts by weight _{2 O 3 -B 2 O 3 -CaO} -B
Using a glass to which aO-based glass was added, a restraining sheet having a thickness of 300 μm was prepared by a doctor blade method, and the restraining sheets were stacked on both sides of the green sheet laminate, at a temperature of 55 ° C. and a pressure of 20 MPa. Was laminated. The laminate was fired in a nitrogen atmosphere containing water vapor at 900 ° C. for 1 hour. (G) Thereafter, the constraining sheets on both sides of the sintered body were removed by a wet blast method until the electrode pad conductor layer was exposed, thereby producing a wiring board.

The X-ray of the wiring board manufactured as described above
The firing shrinkage in the Y direction was as small as 0.1%, and the dimensional change in the plane direction was very small.

Also, by observing the cross section of the electrode pad conductor layer of this wiring board, the thickness near the center of the electrode pad conductor layer and the thickness around the electrode pad conductor layer were measured. Is 20 μm, and the peripheral portion is 10 μm.
It was confirmed that the area near the center was thicker than the periphery.

Further, the average thickness (minimum thickness + maximum thickness) / 2 of the coating layer covering the periphery of the electrode pad was measured and found to be 14 μm.

Then, after 2 μm of Ni plating and 0.1 μm of Au plating were applied to the conductor layer for the electrode pad, a ball terminal having a diameter of 0.5 mm was brazed by solder to measure the bonding strength. In the measurement, when the ball terminal was grasped by a jig and vertically pulled up at a speed of 10 mm / min, the maximum load at which the ball terminal could be removed was taken as the bonding strength. As a result, the joining strength was 5.5 kg.

Comparative Example 1 A wiring board was manufactured in exactly the same manner as in Example 1 except that the step (d) was not performed. As a result, the dimensional change was as good as 0.1%, but in the step (g), when the constraint sheet was removed, the covering layer formed around the conductor layer had been removed. As a result of the peel test, the joining strength was as low as 2.5 kg.

Comparative Example 2 A wiring board was produced in the same manner as in Example 1 except that the steps (d), (f) and (g) were not performed. As a result, the dimensional change was as large as 0.7%, and the bonding strength by the peel test was 5.0 kg, which was better than Comparative Example 1, but lower than the product of the present invention.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a method of manufacturing a wiring board according to the present invention.

2 is an enlarged cross-sectional view of a conductor layer after removing a restraint sheet in a manufacturing process of the wiring board of FIG. 2;

FIG. 3 is a schematic sectional view of a package for housing a semiconductor element as an example of the wiring board of the present invention.

FIG. 4 is an enlarged sectional view of a ring-shaped conductor layer in the package for housing a semiconductor element of FIG. 3;

5 is an enlarged cross-sectional view of a conductor layer for connection pads in the semiconductor device housing package of FIG. 3;

FIG. 6 is a process chart for explaining a conventional method for manufacturing a wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Green sheet 2 Via-hole conductor 3 Conductor layer 4 Coating layer 5 Restraint sheet 6 Insulating substrate

Claims (10)

[Claims] 1. A wiring board having a conductor layer brazed to a metal member on a surface of a ceramic insulating substrate, wherein a ceramic coating layer is formed on at least a part of a periphery of the conductor layer. A wiring board, wherein an exposed portion of the conductor layer is thicker than a peripheral portion covered by a covering layer. 2. The wiring board according to claim 1, wherein the metal member is a connection terminal, and the entire periphery of the conductor layer is embedded in the insulating substrate. 3. The metal member is a lid, wherein the conductor layer is formed in a ring shape on a surface of the insulating substrate, and an inner edge and / or an outer edge of the ring-shaped conductor layer is formed in the insulating substrate. 2. The wiring board according to claim 1, wherein the wiring board is embedded in the wiring board. 4. The wiring board according to claim 1, wherein a plating layer having a thickness of 1 to 10 μm is formed on an exposed surface of the conductor layer. 5. A step of producing a first green sheet from a first ceramic composition; b) a step of forming a conductive layer on a surface of the first green sheet; and c) a step of forming the first green sheet. Coating the first ceramic composition on at least a part of the periphery of the layer; d) forming an additional conductor layer on the surface of the conductor layer that is not coated with the first ceramic composition. E) a second ceramic composition made of a second ceramic composition that is not sintered at the firing temperature of the first ceramic composition, on at least the surface side of the first green sheet after the step d) on which the conductor layer is formed. F) laminating the green sheets; f) firing the laminate after the step e) at a temperature at which the first ceramic composition is fired, but not at which the second ceramic composition is fired; g) after the e) step Baked Things from, method for manufacturing a wiring substrate, characterized by comprising the step of removing the second green sheet, a. 6. The method for manufacturing a wiring board according to claim 5, wherein a metal member is brazed to said conductor layer. 7. The method according to claim 5, wherein the metal member is a connection terminal, and in the step c), a covering layer is formed on the entire periphery of the conductor layer. 8. The metal member according to claim 8, wherein said metal member is a lid.
In the step, the conductor layer is formed in a ring shape on the surface of the first green sheet, and in the step c),
The method according to claim 6, wherein a coating layer is formed on an inner edge and / or an outer edge of the ring-shaped conductor layer. 9. The wiring board according to claim 5, wherein the step f) is performed at a low temperature of 1050 ° C. or less, and the conductor layer is made of a conductor containing copper or silver as a main component. Manufacturing method. 10. The method according to claim 5, further comprising, after the step g), forming a plating layer on the exposed surface of the conductor layer.