JP3508905B2 - Wiring board and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring ceramic substrate in which a plurality of ceramics are laminated, and stable connection by wire bonding with an electronic component such as a semiconductor element mounted in a cavity on the upper surface thereof. Is characterized by.

[0002]

2. Description of the Related Art In general, a wiring board 100 for mounting an electronic component such as a semiconductor element in a cavity 120 provided on the upper surface thereof has a rectangular shape as shown in FIG.
As shown in (B), a plurality of ceramic layers 101 to 112 each having a punched central portion are vertically stacked on the ceramic layer 113 to form a frame portion 130 having an inner peripheral side having a step shape. There is. In the cavity 120, the semiconductor element C is fixed on the ceramic layer 113 that is the bottom surface thereof. Further, each ceramic layer 102-106 and the same 108-
Between 112, metallization layers 116 and 117 for power supply, for example, are arranged on substantially the entire surface in a rectangular frame shape in plan view except both end portions in the width direction. The reason why the metallized layers 116 and 117 are not arranged along the inner and outer ends of the ceramic layers 102 to 106 and 108 to 112 is that the metallized layers 116 and 117 are formed on the inner surface of the cavity 120 later by Ni plating or the like. This is to prevent short circuits between 117.

Further, on the upper surfaces of the ceramic layers 102 and 107 forming the stepped upper surface of the frame portion 130, a large number of narrow connecting pads 122 and 124 whose tip portions are aligned along the cavity 120 are substantially formed. They are arranged in parallel. The connection pads 122 and 124 are electrically connected to a predetermined circuit in the substrate 100 through vias (not shown) that penetrate the metallized layers 116 and 117 in the vertical direction, and the semiconductor elements mounted in the cavity 120. It is connected to C by a wire W. In addition, the wiring board 100
Is manufactured by vertically stacking a screen-printed conductive paste on each surface of green sheets punched into the same number of predetermined shapes to be the ceramic layers 101 to 113, and then firing.

By the way, since each green sheet receives a compressive force in the thickness direction during the above-mentioned lamination, the inner peripheral portions of the ceramic layers 102 to 106 and 107 to 112 in which the metallized layers 116 and 117 do not exist in plan view ( On the side of the cavity 120), the metallized layers 116, 1
In some cases, inclined surfaces K are formed that are gently inclined downward by an amount substantially equivalent to the thickness of 17. Ceramic layers 102 and 107 surrounding the cavity 120
When the inclined surface K is formed on the inner peripheral portion of the wire W, the wire W for connecting the connection pads 122 and 124 provided immediately above the portion and a terminal (not shown) of the semiconductor element C mounted in the cavity 120. When the bonding is performed, the positions of the connection pads 122 and the like shift downward due to the inclined surface K. As a result, the tip of the wire W to be bonded slips from the connection pad 122 or the like and cannot come into contact therewith, so that sufficient pressure or crimping due to microvibration cannot be performed, and each formed in the wiring board 100. There has been a problem that the circuit and the semiconductor element C cannot be electrically connected.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the above conventional techniques, and makes it easy and reliable to connect an electronic component such as a semiconductor element mounted in a cavity to a circuit in a wiring board. It is an object of the present invention to provide a wiring board and a manufacturing method thereof that can be performed.

[0006]

In order to solve the above problems, the present invention is conceived to arrange an insulating layer having a required thickness along the inner peripheral edge of the metallized layer between the ceramic layers. It was done. That is, the wiring board of the present invention is a frame part formed by stacking a plurality of ceramic layers with a cavity part for mounting electronic parts, surrounding the cavity part, and having an inner peripheral side having a stepped cross-section. And a bottom portion fixed to the frame portion so as to form at least the bottom surface of the cavity portion, and a connection pad formed on the floor cross section of the frame portion for connecting to an electronic component, A position formed between at least one or more layers of the plurality of ceramic layers forming the frame portion, the inner peripheral edge of which is substantially directly below the connection pad and lower than the inner peripheral edge of the ceramic layer in plan view. Of the metallized layer formed on the insulating layer, and the insulation provided at least directly under the connection pad in the pull-down portion between the inner peripheral edge of at least one or more metallized layers and the inner peripheral edge of the ceramic layer. When, only including, a thickness of the insulating layer, the metallization layer
It is characterized by being thicker than the thickness .

According to this wiring board, the metallized layer is provided between the ceramic layers, and the insulating layer is disposed in the pull-down portion along the inner peripheral side thereof.
It is possible to eliminate the occurrence of 17 or to suppress it to a very small extent. Moreover, the thickness of the insulating layer is the thickness of the metallized layer.
Since it is thicker than only
After being formed, the difference in thickness from the metallized layer is adjusted by each ceramic
It can also be adjusted for each layer. Of the metallized layer
There is no pull-down part and the metallization extends to the inner edge of the ceramic layer.
Layer is formed, or when the metallized layer is not formed.
Even if the ceramic layer is slightly downward on the cavity side of the ceramic layer
Since the thickness of the insulating layer tends to
It should be slightly thicker than the IZ layer. The insulating layer is
It suffices that it is formed at least in a portion just below the connection pad of the pull-down portion, and it does not have to be formed substantially directly in a portion where the connection pad is not formed. Alternatively, it may be provided in substantially the entire area of the pull-down portion including the portion where the connection pad is formed.

The inclined surface K is formed by the difference in thickness between the region where the metallized layers 116 and 117 are formed and the region where it is not formed (pulled-down portion) as described above. Therefore, as the number of ceramic layers and the number of metallized layers formed between the ceramic layers increases, the total sum of the thickness differences increases. In particular, when the metallized layer has four or more layers, it is important to adjust the thickness difference due to the formation of the insulating layer and eliminate or minimize the inclined surface K. Therefore, the present invention, the frame portion that has have a four or more layers of metallization layers, also includes the wiring substrate.

[0009]

Further, the insulating layer may be selectively formed only between some of the ceramic layers, and the sum of the thickness differences due to the metallized layers between the respective ceramic layers may be adjusted. For example, the insulating layer may be formed every one or two layers of the metallized layer. In this case, the thickness of the insulating layer is preferably about 2 to 3 times the thickness of the metallized layer or slightly thicker than them. As described above, in the mode in which the insulating layer is selectively provided only between some of the ceramic layers, the formation of the insulating layer can be simplified, and the same effect as the mode in which the insulating layers are provided between the ceramic layers can be obtained. Therefore, the present invention, the insulating layer is formed on the withdraw portion of each jumping one layer jump or two layers of said metallization layer also includes a wiring board.

[0011] Incidentally, among the ceramic layer, the thickness of the ceramic layer sandwiched between at least the metallized layers,
A wiring board having a size of 0.25 mm or less may be used . That is,
When the thickness of the ceramic layer is small, the difference in thickness between the region where the metallized layer is formed and the region where it is not formed (pulled-down portion) is large when the total thickness difference of all the ceramic layers and the metallized layer is large. Therefore, the influence on the inclined surface K also increases. Therefore, since the metallized layer is generally formed to have a thickness of 10 to 30 μm, the adjustment of the thickness by the insulating layer becomes more important in the wiring board in which the thickness of the ceramic layer sandwiched between them is 0.25 mm or less.

Further, in the present invention, the cavity portion has a rectangular shape in a plan view, the pull-down portion is formed in a rectangular frame shape in a plan view, and the insulating layer except the corner portion of the pull-down portion. is formed on the side portions, the wiring board are also included. With such a configuration, it is possible to provide a wiring board that can reliably and efficiently connect the semiconductor element or the like mounted in the cavity to the circuit in the wiring board. The insulating layer may be a wiring board made of the same ceramic as the ceramic layer. As a result, the insulating layer is firmly integrated with the vertically adjacent ceramic layers,
It is possible to obtain a wiring board having excellent durability.

Further, in order to obtain the above wiring board, the present invention comprises a step of applying a conductive paste, which becomes the metallized layer after firing, to any surface of a plurality of green sheets which becomes the ceramic layer after firing, at least a portion of the surface of the green sheet, the insulating layer to become an insulating paste after firing along the inner circumference side of the conductive paste, those
There is also provided a method for manufacturing a wiring board, which includes a step of applying the conductive paste thicker than the thickness of the conductive paste . According to such a configuration, it is possible to eliminate the occurrence of the inclined surface or to manufacture the wiring board in a desired quantity reliably and accurately with the number of wiring boards suppressed as much as possible. A method of manufacturing a wiring board in which the insulating paste is made of the same ceramic component as the green sheet may be used . As a result, the wiring board can be reliably and firmly manufactured using only the same kind of ceramic raw material.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment for carrying out the present invention will be described below with reference to the drawings. FIG. 1 (A) is a perspective view showing an embodiment of a wiring board 1 according to the present invention, which has a rectangular cavity portion 2 on its upper surface, and surrounds the cavity portion 2, and has a vertical stepwise cross section. A frame portion 3 having the step surfaces 4 and 5 on the inner peripheral side is formed. A large number of connection pads 6, 8 whose tip portions are aligned along the cavity 2 are arranged substantially parallel to each other on each side of the step surfaces 4, 5. As shown in FIG. 1 (B), the frame portion 3 surrounding the cavity portion 2 is formed by stacking a plurality of ceramic layers 10 to 21 in the vertical direction, and serves as a lower bottom ceramic layer 2.
It is fixed on 2. The ceramic layers 11 to 15 and 16 to 21 forming the frame portion 3 are punched into the same rectangular shape at the center side to form the cavity portion 2 and the stepped surface is formed near the cavity portion 2 of the ceramic layers 11 and 16. 4 and 5 are formed.

In the drawing, the upper ceramic layers 11 to 11 are shown.
Between 15 and between the lower ceramic layers 17 to 21, metallization layers 24 and 26 for power supply, for example, are formed over substantially the entire surfaces thereof. On the inner peripheral sides of the metallized layers 24 and 26, pull-down portions 25 and 27 having a predetermined width are formed, respectively, along the cavity 2 side, where the metallized layers 24 and 26 are not formed . Of these , the insulating layers 28 and 29 are arranged in a rectangular frame shape on the upper surfaces of the ceramic layers 13 and 15 and 18 and 20, respectively.
It almost occupies the inside of 5,27. Such insulating layers 28, 2
9 is thicker than the metallized layers 24 and 26.
Has been formed. For example, as shown in FIG. 2, the metallized layer 24 and the insulating layer 28 are arranged on the ceramic layer 13 along the inner peripheral edge of the metallized layer 24 so that the width of the pull-down portion 25 on the inner peripheral side is as wide as possible. 28 are arranged in a rectangular frame shape.

By arranging the insulating layer 28 and the like as shown in FIG. 1 (B), the inclined surface K in the prior art is eliminated on the step surfaces 4 and 5 of the wiring board 1 or is very small. Since it does not appear, the connecting pads 6 and 8 arranged immediately above the connecting pads 6 and 8 are formed substantially accurately at their original positions. Therefore, the bonding of the pads 6, 8 and the semiconductor element C similar to the one mounted in the cavity 2 by the wire W can be reliably performed. Reference numeral 30 located in the metallized layer 24 in FIG. 2 indicates a via penetrating the metallized layer 24 in the vertical direction with a gap provided between the metallized layer 24, the connection pad 6 and the wiring not shown. It is electrically connected to a circuit provided below the substrate 1. These vias 30 are
The other metallized layers 24 and 26 are also penetrated to electrically connect the pads 6 and 8 to the circuit below the wiring board 1.

[0017] FIG. 3 is a partial cross-sectional view at the same position as Figure 2 an insulated layer of a different arrangement form, FIG. 3 (A),
The metallized layer 46 is formed on the ceramic layer 44 that constitutes a frame part 40, on the inner peripheral side of the withdraw portion 42 thereof, while maintaining a very narrow gap 41 between the metallized layer 46, such metallized layer 46 Insulation layer 4 thicker than
8 shows a state in which 8 is provided. When the insulating layer 48 is disposed with the gap 41, the inner peripheral edge of the metallized layer 46 and the outer peripheral edge of the insulating layer 48 are slightly displaced in the inner and outer directions on the same ceramic layer 44 during manufacturing, as described later. Also,
It is possible to prevent unnecessary convex portions from being formed on the staircase surface above them by overlapping each other.

[0018] FIG. 3 (B) shows a corner portion of the ceramic layer 54 that constitutes a frame portion 50, withdraw unit 52 with placing the metallized layer 56 in a substantially L shape on the upper surface, along its inner peripheral edge except for the corner portion 53 in the thickness than the very narrow keep the gap 51, and the thickness of the metallized layer 56 in strip shape in the respective side portion 55 between the metallized layer 56
The insulating layers 58, 58 are arranged at right angles to each other. Since the connecting pads 6 and 8 are rarely arranged on the step surface (not shown) directly above the corner portion 53,
The insulating layer 58 can be efficiently arranged, and the wire bonding with the connection pad 6 or the like can be reliably performed.

Next, a method of manufacturing the wiring board 1 will be described with reference to FIG. In FIG. 4A, a plurality of green sheets 60 to 71, which are mainly made of alumina and whose central portion is punched out, are prepared.
Conductive pastes 84 and 86 made of a refractory metal such as tungsten and molybdenum, which will be the metallized layers 24 and 26, are applied on the surface of 71 by screen printing or the like on almost the entire surface, and the inner peripheral side is provided with Pull-down part 2
The state where 5, 27 are provided is shown. On the surfaces of the green sheets 61, 66 forming the staircase surfaces 4, 5, a large number of conductive pastes 76, 78 made of the same high melting point metal as described above for obtaining the connection pads 6, 8 are formed. It is applied in the same manner.

Next, as shown in FIG. 4 (B), the pull-down portion 2 on the green sheets 63, 65 and 68, 70.
Insulating pastes 88 and 89, which are made of the same kind of alumina as described above and serve as the insulating layers 28 and 29 after firing, are similarly applied in the layers 5 and 27. That is, the insulating pastes 88 and 89 are applied to each layer of the conductive pastes 84 and 86 slightly thicker than the conductive pastes 84 and 86, thereby suppressing an increase in the number of manufacturing processes. Incidentally, reference numeral 72 in the drawing denotes a green sheet which becomes the ceramic layer 22 which constitutes the bottom portion. And
When these green sheets 60 to 72 are vertically stacked in a predetermined order and fired while applying pressure in the thickness direction by a conventional method, the green sheets 60 to 72 are applied to the ceramic layers 10 to 22 and the conductive paste 76. , 78 to the connection pads 6 and 8, the conductive pastes 84 and 86 to the metallized layers 24 and 26, and the insulating pastes 88 and 89 to the insulating layers 28 and 29, respectively, to obtain the wiring board 1. The conductive pastes 84 and 86 and the insulating pastes 88 and 89 may be applied on the same green sheets 63 and 68 in the reverse order. Further, if a very small gap is provided between the conductive pastes 84 and 86 and the insulating pastes 88 and 89, they can be prevented from overlapping each other even if some positional deviation occurs between them.

Here, the effect of the present invention will be specifically described together with a comparative example. First, the wiring board 1 was manufactured by the above method. The metallized layers 24 and 26 have a thickness of 7 to 12 μm, and the insulating layers 28 and 29 have a thickness of 20 to 30.
μm, and the upper and lower surfaces are metallized layers 24, 26
The thicknesses of the ceramic layers 12 to 14 and the ceramic layers 18 to 20 sandwiched between them are all 0.05 mm. And the upper insulating layer 2
Five pieces each of which 8 was arranged only on the lower ceramic layer 15 (Invention Example 1) and five pieces which were arranged on both the upper and lower ceramic layers 13 and 15 (Invention Example 2) were prepared.
Further, the lower insulating layer 29 is arranged only on the lower ceramic layer 20 (Invention Example 3) and the lower insulating layer 29 is arranged on both upper and lower ceramic layers 18 and 20 (Invention Example 4).
I prepared them individually.

On the other hand, the insulating pastes 88 and 8 having the same shape and dimensions as those described above and serving as the insulating layers 28 and 29.
The same number of wiring boards of the same comparative example as the conventional board 100 manufactured without applying only 9 were prepared. Then, in the vicinity of the central position of each of the stepped surfaces 4 and 5 of each substrate 1 and the like, a position of 0.10 mm from the tip of the connection pads 6 and 8 near the cavity 2 and a position 0.5 mm away from it. Then, after focusing on one side by an optical microscope using the so-called focusing method, it is moved to the other side and moved in the vertical direction until it comes into focus again, that is, the difference in height between inclined surfaces With respect to 1 to 4 and the comparative example, the steps 4 and 5 were measured separately, and the average value and the maximum and minimum values were calculated. The results are shown in FIG. 5 for the staircase surface 4 and each graph in FIG. 6 for the staircase surface 5.

According to the graph of FIG. 5, Invention Examples 1 and 2 as a whole have a smaller moving distance, that is, an inclination degree than that of the Comparative Example, and Invention Example 2 has a smaller amount than Invention Example 1. ing. Also in the graph of FIG. 6, invention examples 3 and 4 similarly have a smaller degree of inclination than the comparative example, and invention example 4 is even smaller than invention example 3. From these results, it is possible to understand the effect of the present invention by arranging the insulating layers 28 and 29, and it is possible to control the degree of inclination depending on the number of the insulating layers 28 and 29 arranged. Is also clear. Therefore, the metallized layer 2
If the insulating layers 28 and 29 having the same thickness are arranged along all the inner peripheral sides of the wirings 4 and 26, the generation of the inclined surface in the floor cross sections 4 and 5 can be most suppressed, but the manufacturing process is considerably performed. As described above, the number of metallization layers 2 increases.
From the viewpoint of manufacturing, it is desirable to dispose the insulating layers 28 and 29 on the inner peripheral side of each of the layers 4 and 26 or every two layers thereof.

The present invention is not limited to the form described above. For example, the material of the ceramic layer and the insulating layer is not limited to alumina, aluminum nitride,
Ceramics such as glass ceramics and mullite can also be used. The material of the ceramic layer and the insulating layer is not limited to the form in which the same type of ceramic is used in combination, but different materials may be used in consideration of firing shrinkage and the like. The material of the metallized layer is not limited to Mo and W, but may be Mo-M.
It is also possible to apply n, Cu, Ag, Ag-Pd, Ag-Pt, or the like. Further, the present invention can be applied to all wiring boards including a so-called pin grid array type having a cavity portion and a leadless chip carrier, and further applied to a multi-chip module having a plurality of semiconductor elements mounted in the cavity portion. it can. Moreover, the electronic components mounted in the cavity are not limited to semiconductor elements including transistors, EFTs, etc., but capacitors, resistors, inductors, SAs, etc.
A W filter and the like are also included.

[0025]

According to the wiring board of the present invention described above, according to the present invention is formed by laminating a plurality of ceramic layers, its
There is a metallization layer and a thicker insulating layer between these layers.
Since it is formed at a fixed position, it becomes easy to provide a large number of connection pads arranged on the stepped surface on the inner peripheral side of the frame portion at the original predetermined position . Therefore, it becomes possible to easily and surely perform wire bonding for connecting the pad and an electronic component such as a semiconductor element mounted in the cavity. Further, according to the manufacturing method of the present invention, it is possible to reliably and accurately provide the above wiring board in a desired amount .

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of a wiring board of the present invention, and FIG. 1B is a sectional view taken along line BB in FIG.

FIG. 2 is a partial end view taken along the line EE in FIG.

3 (A) and 3 (B) are partial end views similar to FIG. 2, showing different forms of insulating layers.

4A and 4B are schematic cross-sectional views showing the manufacturing process of the wiring board of the present invention.

FIG. 5 is a graph showing distributions of height differences on the inclined surfaces of Inventive Examples 1 and 2 and Comparative Example.

FIG. 6 is a graph showing distributions of height differences on inclined surfaces of Inventive Examples 3 and 4 and Comparative Example.

FIG. 7A is a perspective view showing a conventional wiring board, and FIG.
It is a BB sectional view in (A).

[Explanation of symbols]

1 ……………………………… Wiring board 2 ……………………………… Cavity 3, 40, 50 ………… Frame part 4,5 ………………………… Stairs 6,8 ………………………… Connection pad 10-21, 44, 54 ... Ceramic layer 22 ……………………………… Ceramic layer (bottom) 24, 26, 46, 56 ... Metallized layer 25,27,42,52 ... Downward part 28,29,48,58 ... Insulating layer 53 ……………………………… Corner 55 ………………………… Hedge 60-72 ……………… Green sheet 84,86 ……………… Conductive paste 88,89 ……………… Insulation paste

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 23/12

Claims (5)

(57) [Claims] 1. A cavity portion for mounting an electronic component, and a frame portion formed by laminating a plurality of ceramic layers, surrounding the cavity portion, and having an inner peripheral side having a stepwise cross-section, at least the above. A wiring board including a bottom portion fixed to the frame portion so as to form a bottom surface of the cavity portion, and a connection pad formed on the floor cross section of the frame portion for connecting to an electronic component, the frame portion Is formed between at least one or more layers of the plurality of ceramic layers forming the inner peripheral edge, and the inner peripheral edge is formed at a position substantially directly below the connecting pad and lower than the inner peripheral edge of the ceramic layer in plan view. A metallization layer; and an insulating layer provided at least substantially directly under the connection pad in a pull-down portion between the inner edge of at least one metallization layer and the inner edge of the ceramic layer. The thickness of the insulating layer is the thickness of the metallized layer.
A wiring board characterized by being thicker than . 2. A wiring board according to claim 1, wherein the frame portion has a four or more layers of the metallization layer, and wherein the. Wherein the insulating layer is one layer jump or are formed on the withdraw portion of each jumping two-layer wiring board according to claim 1 or 2, characterized in that of said metallized layer. 4. The cavity has a rectangular shape in plan view.
The pull-down portion is formed in a rectangular frame shape in plan view,
The insulating layer is the
The wiring board according to any one of claims 1 to 3, wherein the wiring board is formed on a side portion . 5. The wiring board according to claim 1.
A method of manufacturing a plurality of green sheets after firing becomes the ceramic layer
On either surface of the metal, which will become the metallized layer after firing.
Step of applying an electric paste, and after firing on at least part of the surface of the green sheet
Insulating paste that becomes the insulating layer of the conductive paste
Along the inner circumference side, it should be thicker than the thickness of the conductive paste.
The step of clothing is included before and after.
Method of manufacturing line substrate .