JP6884062B2 - Wiring board - Google Patents

Description

The present invention relates to a wiring board.

Conventionally, as described in Patent Documents 1 and 2, a wiring board in which a connection pad having a multilayer structure in which a Cu layer, Ni plating, and Au plating are sequentially laminated on an adhesion layer is formed has been used.
A wiring board is constructed by sequentially laminating an adhesion layer made of Ti etc., a wiring layer made of Cu etc., a barrier layer made of Ni etc., and a bonding layer made of Au etc. on an insulating substrate made of ceramic or the like. It can be soldered to the upper surface of the bonding layer.
Here, the adhesion layer improves the adhesion between the insulating substrate and the wiring layer. The wiring layer forms an electrical conduction path. The barrier layer prevents the solder component (tin) from diffusing into the wiring layer. The joint layer ensures solder wettability.

Japanese Unexamined Patent Publication No. 4-144190 Japanese Unexamined Patent Publication No. 6-151618

As shown in FIG. 5 as an outline of the process, according to the additive method, a resist 6 having an opening of a desired wiring pattern on a metal film (2, 3) composed of a Ti layer 2 and a Cu layer 3 is attached to a photomask 7. After forming by exposure through the resist 6, Ni / Au plating 4 and 5 are applied to the openings of the resist 6, and after removing the resist 6, the exposed metal film (2, 3) is removed from the Ni / Au plating 4 and 5. A high-definition wiring pattern can be obtained.
However, according to the additive method, since the side surface of the Cu layer 3 is exposed as shown in FIG. 6, there is a problem that the reliability is lowered due to the corrosion of the Cu layer 3 and the like.
On the other hand, after forming a metal film (2, 3) in a desired wiring pattern by the subtractive method showing the outline of the process in FIG. 7, Ni / Au plating 4 and 5 are applied to the Cu layer 3 with a predetermined thickness. As shown in FIG. 8, plating having the same thickness is formed on the side surface of the Cu layer 3.
Therefore, since the side surface of the Cu layer 3 is protected by Ni / Au plating 4 and 5, the Cu layer 3 is less likely to corrode and has high solder resistance.
However, since plating of the same thickness is formed on the side surface of the Cu layer 3, the wiring pattern becomes thicker than the plating layer thickness on both sides, and the thickness of the plating varies widely. There is a problem that it is difficult to obtain a pattern.

The present invention has been devised in view of the above conventional problems, and an object of the present invention is to improve the corrosion resistance and fineness of wiring on a wiring board.

According to the present invention, in a wiring board in which an adhesion layer and a wiring layer are sequentially laminated on an insulating substrate, the edge portion of the adhesion layer extends outward from the side surface of the wiring layer, and the wiring in the thickness direction. The main surface of the insulating substrate that protrudes to the layer side and covers the side surface of the wiring layer and on which the adhesion layer is formed is the adhesion layer side in the thickness direction in a region outside the edge portion of the adhesion layer. A protruding portion is formed, and the protruding portion covers the side surface of the edge portion of the close contact layer which is opposite to the side surface of the wiring layer, and the protruding portion is from the insulating substrate side to the wiring layer side. It is characterized in that the thickness dimension in the direction perpendicular to the side surface of the wiring layer gradually decreases toward the tip in the protruding direction.
The wiring board of the present invention is preferably formed by sequentially laminating a barrier layer and a bonding layer on the wiring layer, and the protruding portion of the insulating substrate protrudes at least to the interface position between the wiring layer and the barrier layer. It is characterized by being.
According to the present invention, in a wiring board in which an adhesion layer and a wiring layer are sequentially laminated on an insulating substrate, the edge portion of the adhesion layer extends outward from the side surface of the wiring layer, and the wiring in the thickness direction. The main surface of the insulating substrate that protrudes to the layer side and covers the side surface of the wiring layer and on which the adhesion layer is formed is the adhesion layer side in the thickness direction in a region outside the edge portion of the adhesion layer. A protruding portion is formed, and the protruding portion covers the side surface of the edge portion of the adhesion layer which is opposite to the side surface of the wiring layer, and the barrier layer and the bonding layer are sequentially laminated on the wiring layer. Therefore, the protruding portion of the insulating substrate is characterized in that it protrudes at least to the interface position between the wiring layer and the barrier layer.

In the wiring board of the present invention, preferably, the thickness dimension of the edge portion of the adhesion layer gradually decreases in the direction perpendicular to the side surface of the wiring layer toward the tip in the protruding direction from the insulating substrate side to the wiring layer side. It is characterized by doing.

The wiring board of the present invention is preferably formed by sequentially laminating a barrier layer and a bonding layer on the wiring layer, and the edge portion of the adhesion layer projects at least to the interface position between the wiring layer and the barrier layer. It is characterized by being.

The wiring board of the present invention is preferably characterized in that the edge portion of the adhesion layer protrudes at least to the interface position between the barrier layer and the bonding layer.

According to the present invention, the corrosion resistance and fineness of wiring on a wiring board are improved.

It is a vertical sectional view which shows the wiring board which concerns on 1st Embodiment of this invention. It is a vertical sectional view which shows the wiring board which concerns on 1st Embodiment of this invention. It is a vertical sectional view which shows the wiring board which concerns on 2nd Embodiment of this invention. It is a vertical sectional view which shows the wiring board which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the process of an additive method. It is a vertical cross-sectional view which shows the wiring board of a conventional example by an additive method. It is a schematic diagram which shows the process of the subtractive method. It is a vertical cross-sectional view which shows the wiring board of a conventional example by a subtractive method.

An embodiment of the present invention will be described below with reference to the drawings. The following is an embodiment of the present invention and does not limit the present invention.

[First Embodiment]
First, the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the wiring board according to the first embodiment of the present invention includes a ceramic substrate 1 as an insulating substrate, a Ti layer 2 as an adhesion layer sequentially laminated on the ceramic substrate 1, and Cu as a wiring layer. It has a layer 3.
The insulating substrate (1) can be selected from aluminum oxide sintered body, mulite sintered body, silicon carbide sintered body, aluminum nitride sintered body, glass ceramics sintered body and the like, and is an insulating substrate. When (1) is made of, for example, an aluminum oxide sintered body, an appropriate organic solvent and solvent are added and mixed with raw material powders such as alumina, magnesia, calcia, and silica to form a muddy sinter, and this is performed by the doctor blade method. A ceramic green sheet (ceramic raw sheet) is formed by adopting the or calendar roll method, etc., and then the ceramic green sheet is appropriately punched to form a predetermined shape and fired at a high temperature (about 1600 ° C). Manufactured by doing.

The edge portion 21 of the Ti layer 2 extends outward (in the X direction) from the side surface 31 of the Cu layer 3 and is formed by being adhered to the main surface 10 of the ceramic substrate 1. The edge portion 21 of the Ti layer 2 projects toward the Cu layer 3 side (Z direction) in the thickness direction and covers the side surface 31 of the Cu layer 3.
In such a structure, when the Ti layer 2 is processed by a method of colliding ions and etching, the Ti particles of the Ti layer 2 sputtered with ions are reattached to the Ti layer 2 and projected in the Z direction, while the Cu layer 3 is formed. It can be configured by adhering to the side surface 31 of the above. At this time, as shown in FIG. 1, the edge portion 21 of the Ti layer 2 is in a direction perpendicular to the side surface 31 of the Cu layer 3 toward the tip (Z direction) in the protruding direction from the ceramic substrate 1 side to the Cu layer 3 side. The thickness dimension in the (X direction) is gradually reduced.

The adhesion layer (2) improves the adhesion between the insulating substrate (1) and the wiring layer (3). The wiring layer (3) forms an electrical conduction path. The adhesion layer (2) is adhered and formed on the insulating substrate (1) by a thin film forming technique such as a thin film deposition method or an ion plating method. The wiring layer (3) is adhered by a thin film forming technique such as a thin film deposition method, an ion plating method, a sputtering method, or a plating method.
If the thickness of the adhesion layer (2) is less than 100 angstroms, it tends to be difficult to firmly bond the wiring layer (3) to the insulating substrate (1), and if it exceeds 10,000 angstroms, the adhesion layer (2) Since the adhesive strength between the insulating substrate (1) and the adhesive layer (2) tends to decrease due to the internal stress when the film is adhered by the thin film forming technique, the range of 100 to 10000 angstroms is good, preferably 300 to. The thickness of 2000 angstroms should be optimally 500 to 1500 angstroms.
If the thickness of the wiring layer (3) is less than 0.5 μm, the conduction resistance of the circuit wiring tends to be high and it tends to be unsuitable as a wiring board. Therefore, the thickness of the wiring layer (3) is 0.5 μm or more, more preferably 1 μm or more. The thickness should be good.

As shown in FIG. 2, Ni plating 4 as a barrier layer and Au as a bonding layer are applied to the structure in which the edge portion 21 of the Ti layer 2 projects upward and covers the side surface 31 of the Cu layer 3 of the upper layer. Plating 5 is applied. That is, after forming the edge 21 of the Ti layer 2 in the dry etching process of the Ti layer 2 by the subtractive method showing the outline of the process in FIG. 7, Ni plating 4 and Au plating 5 are sequentially coated on the upper surface of the Cu layer 3. Let me wear it.
Then, since the side surface 31 of the Cu layer 3 is covered with the edge portion 21 of the Ti layer 2, it is possible to prevent the Ni / Au platings 4 and 5 from being formed on the side surface 31 of the Cu layer 3. Further, since Ti is a difficult-to-plate metal, Ni / Au platings 4 and 5 are not formed on the edge portion 21 of the Ti layer 2.
As a result, the Ni / Au platings 4 and 5 are not arranged on the side of the Cu layer 3, and the wiring pattern is not thickened, so that a high-definition wiring pattern is formed.
Further, since the side surface 31 of the Cu layer 3 is covered with the edge portion 21 of the Ti layer 2, that is, the Cu layer 3 is not exposed, the corrosion resistance of the wiring is good, the solder resistance is high, and the reliability is high. improves.

The barrier layer (4) prevents the solder component (tin) from diffusing into the wiring layer (3). The joint layer (5) ensures solder wettability.
In the barrier layer (4), when the bonding layer (5) is firmly adhered to the wiring layer (3) and the electronic components are electrically connected to the wiring layer (3) via the solder, the solder is applied to the wiring layer (3). And effectively prevent the formation of fragile intermetallic compounds between the solder and the wiring layer (3).
If the thickness of the barrier layer (4) is less than 0.4 μm, the adhesive strength between the wiring layer (3) and the bonding layer (5) decreases, and electronic components are electrically connected to the wiring layer (3) via soldering. The solder absorbs the wiring layer (3), a fragile intermetallic compound is formed between the solder and the wiring layer (3), and when the distance exceeds 5.0 μm, the wiring layer (3) The wiring layer (3) itself is peeled off from the insulating substrate (1) due to the internal stress when the barrier layer (4) is adhered onto the barrier layer (4). Therefore, the thickness of the barrier layer (4) is specified in the range of 0.4 μm to 5.0 μm.
The barrier layer (4) is adhered to the wiring layer (3) to a predetermined thickness by subjecting the circuit wiring to nickel plating as in the present embodiment.
Further, a bonding layer (5) is adhered to the upper surface of the barrier layer (4), and the bonding layer (5) is bonded when electronic components are bonded to circuit wiring via solder and electrically connected. It has the effect of strengthening the strength, and is adhered to a predetermined thickness by adopting a plating method or the like on the upper surface of the barrier layer (4).
If the thickness of the bonding layer (5) is less than 0.05 μm, the bonding strength becomes weak when electronic components are electrically connected to the circuit wiring via solder, and if the thickness exceeds 2.0 μm, the bonding layer (5) A large amount of fragile intermetallic compounds are formed between 5) and the solder that connects the electronic components, and the reliability of the connection of the electronic components deteriorates. Therefore, the thickness of the bonding layer (5) is specified in the range of 0.05 μm to 2.0 μm.

As shown in FIGS. 1 and 2, the edge portion 21 of the Ti layer 2 is perpendicular to the side surface 31 of the Cu layer 3 from the ceramic substrate 1 side toward the tip (Z direction) in the protruding direction toward the Cu layer 3 side. The thickness dimension in the above direction (X direction) is gradually decreasing.
With such a structure, the stress applied to the tip portion 21a of the edge portion 21 of the Ti layer 2 in the protruding direction can be reduced, and the edge portion 21 of the Ti layer 2 can be prevented from peeling off.

As shown in FIG. 2, it is preferable that the edge portion 21 of the Ti layer 2 projects at least to the interface position between the Cu layer 3 and the Ni plating 4.
With such a structure, it is possible to prevent the Ni plating 4 from spreading wider than the width of the Cu layer 3. This is because Ti is a difficult-to-plate metal, and the edge portion 21 of the Ti layer 2 is arranged adjacent to the side surface 31 of the Cu layer 3 and extends to the upper surface of the Cu layer 3.

Further, as shown in FIG. 2, it is preferable that the edge portion 21 of the Ti layer 2 projects at least to the interface position between the Ni plating 4 and the Au plating 5.
With such a structure, it is possible to prevent the Au plating 5 from spreading wider than the width of the Cu layer 3. This is because Ti is a difficult-to-plate metal, and the edge portion 21 of the Ti layer 2 is arranged adjacent to the side surface 31 of the Cu layer 3 and extends to the upper surface of the Ni plating 4.

[Second Embodiment]
Next, the second embodiment of the present invention will be described with reference to FIGS. 3 and 4. As shown in FIGS. 3 and 4, the wiring board according to the second embodiment of the present invention has a protruding portion 11 that covers the side surface 21b of the edge portion 21 of the Ti layer 2 with respect to the first embodiment. It is formed on the main surface 10, and other than that, it is the same as that of the first embodiment.

Similar to the first embodiment, the edge portion 21 of the Ti layer 2 is formed, the main surface 10 of the ceramic substrate 1 in the adjacent region of the edge portion 21 is exposed, and then the ceramic substrate 1 sputtered with ions is further configured. The protruding portion 11 is formed by reattaching the particles of the material to be used to the ceramic substrate 1 and projecting them in the Z direction while adhering them to the side surface 21b of the edge portion 21 of the Ti layer 2 (FIG. 3). At this time, the main surface 10 of the ceramic substrate 1 has a lower surface that is lowered to the side opposite to the side to which the Ti layer 2 is adhered via the protrusion 11.
After forming the protruding portion 11, Ni plating 4 and Au plating 5 are sequentially adhered to the upper surface of the Cu layer 3 in the same manner as in the first embodiment.

In the wiring board according to the present embodiment, the main surface 10 of the ceramic substrate 1 on which the Ti layer 2 is formed is a region outside the edge 21 of the Ti layer 2 and is on the Ti layer 2 side in the thickness direction (Z direction). A protruding portion 11 is formed. The protruding portion 11 covers the side surface 21b of the edge portion 21 of the Ti layer 2, which is on the opposite side of the side surface 31 of the Cu layer 3.
Since the edge 21 of the Ti layer 2 attached to the side surface 31 of the Cu layer 3 has low adhesion, there is a concern that the film may peel off. However, according to the structure of the present embodiment, the edge portion 21 of the Ti layer 2 can be reinforced by adhering the ceramic material to the outer side surface 21b of the edge portion 21 and rebonding the ceramic material, and the Ti layer 2 can be reinforced. The peeling of the edge portion 21 can be suppressed. Further, by further providing an insulating material layer on the difficult-to-plating Ti layer 2, it is possible to further make it difficult to apply plating.

Further, the protruding portion 11 of the ceramic substrate 1 projects at least to the interface position between the Cu layer 3 and the Ni plating 4.
According to such a structure, since the protruding portion 11 is formed high to the position where it reaches the height of the Ni plating 4, the reinforcement of the edge portion 21 of the Ti layer 2 can be further strengthened.

1 Ceramic substrate (insulated substrate)
2 Ti layer (adhesion layer)
3 Cu layer (wiring layer)
4 Ni plating (barrier layer)
5 Au plating (bonding layer)
6 Resist 7 Photomask 11 Protruding part of ceramic substrate 21 Edge of Ti layer 31 Side surface of Cu layer

Claims (6)

In a wiring board in which an adhesion layer and a wiring layer are sequentially laminated on an insulating substrate,
The edge portion of the adhesion layer extends outward from the side surface of the wiring layer, protrudes toward the wiring layer side in the thickness direction, and covers the side surface of the wiring layer .
The main surface of the insulating substrate on which the adhesion layer is formed forms a protrusion protruding toward the adhesion layer in the thickness direction in a region outside the edge portion of the adhesion layer, and the protrusion is the wiring. It covers the side surface of the edge of the adhesion layer, which is the opposite side of the side surface of the layer.
The protruding portion is a wiring board characterized in that the thickness dimension in the direction perpendicular to the side surface of the wiring layer gradually decreases toward the tip in the protruding direction from the insulating substrate side to the wiring layer side. A barrier layer and a bonding layer are sequentially laminated on the wiring layer,
The wiring board according to claim 1, wherein the protruding portion of the insulating substrate protrudes at least to the interface position between the wiring layer and the barrier layer. In a wiring board in which an adhesion layer and a wiring layer are sequentially laminated on an insulating substrate,
The edge portion of the adhesion layer extends outward from the side surface of the wiring layer, protrudes toward the wiring layer side in the thickness direction, and covers the side surface of the wiring layer.
The main surface of the insulating substrate on which the adhesion layer is formed forms a protrusion protruding toward the adhesion layer in the thickness direction in a region outside the edge portion of the adhesion layer, and the protrusion is the wiring. It covers the side surface of the edge of the adhesion layer, which is the opposite side of the side surface of the layer.
A barrier layer and a bonding layer are sequentially laminated on the wiring layer,
A wiring board characterized in that the protruding portion of the insulating substrate protrudes at least to the interface position between the wiring layer and the barrier layer. The edge of the adhesion layer is characterized in that the thickness dimension in the direction perpendicular to the side surface of the wiring layer gradually decreases toward the tip in the protruding direction from the insulating substrate side to the wiring layer side. The wiring board according to any one of 1 to 3. A barrier layer and a bonding layer are sequentially laminated on the wiring layer,
It said edge portion of the adhesive layer, the wiring board according to claims 1 to any one of claims 4, characterized in that protrudes at least the wiring layer to the interface position between the barrier layer. The wiring board according to claim 5 , wherein the edge portion of the adhesion layer projects at least to the interface position between the barrier layer and the bonding layer.

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