JPH10173083A - Wiring board for mounting electronic component and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board wherein an electronic component mounting part on the board surface is flattened and an electronic component can be rigidly fixed, and its manufacturing method, regarding a wiring board on the surface of which an electronic component like an IC chip is mounted. SOLUTION: A wring board 1 for mounting an electronic component has a surface 4a on which an IC chip 2 is mounted, a plurality of insulating layers 4-8 composed of ceramic, and metallized wirings 12 arranged between the insulating layers 4-8. Insulating parts 20 are buried in the following; at least the vicinity of the metallized wirings, 12 which are arranged between the first insulating layer 4 and the second insulating layer 5 adjacent to the layer 4 and positioned just under the mounting part of the IC chip 2, or a part between the wirings 12, or the part between the wirings 12 and the vicinity of the wirings 12. The same kind of ceramic as the insulating layers 4-8 can be used for the insulating parts 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board on which electronic components such as an integrated circuit chip (hereinafter, also referred to as an IC chip), a transistor, and a capacitor are mounted on a surface and a method of manufacturing the same. The present invention relates to a wiring substrate having a flat surface.

[0002]

2. Description of the Related Art In general, a ceramic wiring board on which an IC chip is mounted on its surface is formed by printing a conductor paste of a refractory metal such as tungsten or molybdenum on a green sheet made of alumina or the like by screen printing or the like. It is manufactured by providing a conductive paste layer having a circuit pattern, laminating a plurality of green sheets having the conductive paste layer, pressing and bonding, and then firing. On the other hand, in response to the recent demand for miniaturization and thinning, the wiring board for mounting the IC chip has also been required to be smaller and thinner. In some cases, a conductor wiring layer formed of metallized wiring is provided.

For example, a wiring board 50 for mounting an IC chip, whose longitudinal section is shown in FIG. 4 (A), is formed by laminating a plurality of insulating layers 52 to 56 made of ceramics. A metallized wiring 51 is buried between the insulating layer 53 of FIG. Around the first insulating layer 52, frame-shaped insulating layers 55 and 56 are laminated so as to have a stepped cross section, and a metallized surface (not shown) of the surface 52a of the first insulating layer 52 surrounded by these layers. On the layer (so-called die attach), I
A cavity 58 for mounting the C chip is formed. A required number of connection pads 59 are provided near the inner periphery of the upper surface of the frame-shaped insulating layer 55 to connect the IC chip to the conductor wiring layer including the metallized wiring 51 and the like.

By the way, when such a wiring board 50 is manufactured, the surface 52a of the first insulating layer 52 is
A projection 57 due to the thickness of the metallized wiring 51 may be formed above a position where the metallized wiring 51 is buried. This projection 57
Tends to occur more noticeably as the first insulating layer 52 is thinner. Then, as shown in FIG. 4B, the first insulating layer 52 is formed.
For example, on the IC chip mounting portion on the surface 52a of
The brazing material 62 preformed from Au-Si is placed, and the IC chip 60 is placed on the upper surface thereof, and then heated to about 400 ° C. to fix the IC chip 60. However, if the protrusions 57 exist on the surface 52a of the first insulating layer 52, the brazing material 6 between the protrusions 57 when the IC chip 60 is fixed.
In some cases, a gap S is generated in 2 and the adhesion of the IC chip 60 may be insufficient. Further, in order to prevent the generation of the gap S, there is a method of increasing the use amount of the brazing material 62 or the like, but there is a problem that the cost is increased. A similar problem occurs when the IC chip 60 is fixed by a brazing paste or a resin-based adhesive.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and eliminates or reduces projections on the mounting portion of the IC chip and other electronic components.
An object of the present invention is to provide a wiring board for mounting electronic components and a method of manufacturing the same, in which a gap is not generated inside the brazing material without increasing the amount of brazing material used.

[0006]

The present invention solves the above-mentioned problems by embedding another insulator near metallized wiring located immediately below a mounting portion of an electronic component and between the wirings. The present invention has been conceived to prevent a projection from being formed on the surface of the mounting portion. That is, the electronic component mounting wiring board of the present invention has a surface for mounting electronic components, and has an insulating layer made of a plurality of ceramics and a metallized wiring disposed between the insulating layers. A wiring board, disposed between a first insulating layer having the surface and a second insulating layer adjacent thereto and at least near a metallized wiring located immediately below the electronic component mounting portion; An insulating portion is buried between the metallized wirings, or between the metallized wirings and in the vicinity of the metallized wirings. According to such a configuration, since the insulating portion is buried in the vicinity of the metallized wiring and between the wirings, no projection is formed on the surface of the electronic component mounting portion, or it can be made extremely small, so that the electronic component can be fixed. A gap can be prevented from being formed in the brazing material or the like.

[0007] The present invention also includes a wiring board for mounting an electronic component, wherein the insulating portion covers either the first insulating layer side or the second insulating layer side of the metallized wiring. According to such a configuration, since there is no gap between the insulating portion and the metallized wiring, the surface of the electronic component mounting portion becomes flatter, and projections are less likely to occur. An electronic component mounting wiring board in which the insulating portion is buried wider than immediately below the electronic component mounting portion on the surface is also included. According to this configuration, it is difficult for projections to be reliably formed on the surface of the electronic component mounting portion, and a wide surface including the mounting portion is flattened, thereby making it easier to mount the electronic component. Further, a wiring board for mounting an electronic component in which the insulating portion is made of the same type of ceramic as the insulating layer is also included.
According to such a configuration, an insulating portion having the same characteristics (coefficient of thermal expansion and thermal conductivity) as the first and second insulating layers can be obtained, and the inside of the substrate can be integrally and firmly formed of the same type of ceramic. Manufacturing can also be easily performed. Also, a wiring board in which the thickness of the first insulating layer is in the range of 0.01 to 0.65 mm is included. The reason why the thickness is set to 0.01 mm or more is that the thickness is substantially the minimum as a ceramic insulating layer.
The reason why the thickness is 0.65 mm or less is that if the thickness is larger than this, there is a tendency that projections are less likely to occur.

Further, the present invention provides a method of manufacturing each of the above-mentioned wiring boards, that is, a method in which the lower surface of the green sheet which becomes the first insulating layer after firing or the upper surface of the green sheet which becomes the second insulating layer is fired. After forming a conductive paste layer to be the metallized wiring later, an insulating paste is applied so as to substantially cover at least a portion of the conductive paste layer located immediately below the electronic component mounting portion, and the second conductive paste layer is formed thereon. A green sheet to be an insulating layer or a first insulating layer is laminated and fired, and a method for manufacturing a wiring board for mounting electronic components is also included. According to this method, it is possible to efficiently produce a substrate having a surface without the projections or a very small surface by adding only a few steps. Furthermore, the present invention also includes a method of manufacturing a wiring board in which the ceramic material contained in the insulating paste is the same type of ceramic material as the green sheets serving as the first and second insulating layers. According to this method, it can be manufactured at low cost. In addition, since the same firing shrinkage and thermal expansion coefficient as those of the green sheet serving as the insulating layer can be provided, problems such as cracks do not occur during firing, and the insulating layer and the insulating portion are integrally and firmly integrated. A bonded wiring board can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view showing a state in which an IC chip 2 is mounted on the surface of a wiring board 1 of the present invention. The wiring substrate 1 has a substantially flat rectangular shape as a whole,
As shown in FIG. 1B, a plurality of insulating layers 4, 5, 6 made of ceramic and a rectangular frame-shaped insulating layer 7 made of ceramic provided around the surface 4 a of the insulating layer 4 in a stepwise manner. 8
Are integrally laminated. Metallized wirings 12 and the like are provided between the insulating layers 4 to 8, and vias (not shown) that conduct between these metallized wirings are formed through the insulating layers 4 to 8. I have. On the inner peripheral surface of the step-like insulating layer 7, connection pads 9 for conducting the conductor wiring layer to the IC chip 2 via thin metal wires (not shown) are provided along each side. The required number is provided.
Further, a cavity 11 is formed surrounded by the insulating layers 7 and 8.

For example, between the first insulating layer 4 having the surface 4a on which the IC chip 2 is mounted and the second insulating layer 5 adjacent below the first insulating layer 4, the upper surface of the insulating layer 5 in FIG. An insulating portion 20 is buried between the wirings 12 in the metallized wiring 12 provided in the vicinity and in the vicinity thereof, and covers the wiring 12 on the first insulating layer 4 side. It should be noted that a metallized layer (not shown) is formed on a portion of the surface 4a exposed to the cavity 11 side. The insulating portion 20 is made of the same type of ceramic as the insulating layers 4 to 8, has a thickness substantially similar to the thickness of the wiring 12, and has a thickness of I in plan view.
It is formed wider than immediately below the mounting portion of the C chip 2. By providing such an insulating portion 20, the protrusions which have conventionally occurred on the surface 4a due to the metallized wiring 12 are eliminated, and the surface 4a has a flat IC chip mounting portion. Therefore, Ni plating and Au plating on the surface 4a
After plating, for example, a brazing material 22 preformed in the form of a thin plate of Au-Si is placed thereon, and the IC chip 2 is placed from above and heated to about 400 ° C. to fix the soldering material. There is hardly any gap in the inside of the member 22, and the IC chip 2 is firmly fixed at a predetermined position on the surface 4a in a predetermined posture. The insulating portion 20 is provided only in the vicinity of the metallized wiring 12 between the first insulating layer 4 which affects the flatness of the surface 4a and the second insulating layer 5 adjacent thereto.

Next, a method of manufacturing the wiring board 1 will be described. In order to form each of the insulating layers 4 to 8, a green sheet made of alumina or the like is prepared, and is formed into a predetermined shape by punching or the like according to each of the insulating layers 4 to 8. Next, a desired conductive paste layer is formed on the surface of each green sheet by screen printing a conductive paste containing a powder of a high melting point metal such as tungsten or molybdenum or an alloy thereof. Then, of the conductive paste layers formed on the upper surface of the green sheet to be the second insulating layer 5,
Alumina-based insulating paste using a ceramic material similar to the green sheet is screen-printed on the conductor paste layer immediately below the IC chip mounting portion, between the conductor paste layers, and in the vicinity thereof. Then, the insulating paste slightly flows and becomes thin on the conductive paste layer, and becomes an insulating paste layer having substantially the same height as a whole.

When the green sheets are laminated and pressed in a predetermined order, the alumina-based insulating paste layer is formed between the green sheet serving as the first insulating layer 4 and the green sheet serving as the second insulating layer 5. Located in. Thereafter, when fired, each green sheet becomes each of the insulating layers 4 to 8 of ceramic, the alumina-based insulating paste layer becomes the insulating portion 20, and the surface 4a of the first insulating layer 4 becomes flat. Can be obtained.

Here, the effects of the wiring board of the present invention will be compared with those of a conventional wiring board. A substrate 1 and 50 made of the same alumina and having the same cross-sectional structure as those of FIGS. 1B and 4A are prepared, and the thickness of the first insulating layers 4 and 52 is 0.25 mm. The thickness of the other insulating layers including the second insulating layers 5 and 53 is 0.5 mm, and the thickness of the metallized wirings 12 and 51 formed on the second insulating layers 5 and 53 is 15 μm.
And An insulating portion 20 made of alumina was embedded in the substrate 1 so as to cover the metallized wiring 12 with a thickness of 15 to 20 μm. The average heights of the protrusions on the surfaces 4a and 52a serving as the IC chip mounting portions of the substrates 1 and 50 were 2 μm and 12 μm, respectively. Also, the surface 4a,
By changing the thickness of the first insulating layers 4 and 52 having 52a, the heights of the protrusions on the respective surfaces 4a and 52a were measured. Table 1 shows the results. Each data shows an average value of 20 substrates 1 and 50 measured by a contact type surface roughness meter.

[0014]

[Table 1]

From the results shown in Table 1, the height of the projections on the substrate 1 of the present invention was in a very small range of 2 to 3 μm, whereas the height of the projections on the substrate 50 of the comparative example was 2 μm. ~
The thickness of the first insulating layer 52 tended to be higher as the thickness of the first insulating layer 52 became thinner. This is because both are more susceptible to the influence of the metallized wirings 12 and 51 as the first insulating layers 4 and 52 are thinner. But,
In the substrate 1 of the present invention, the height of the projections becomes very small even if the first insulating layer 4 is thin, whereas in the substrate 50 of the comparative example, when the first insulating layer 52 becomes thin, the projections increase rapidly. I have.
From this, it is apparent that the surface 4a was flattened by burying the insulating portion 20 in the substrate 1. When the first insulating layers 4 and 52 are as thick as 0.80 mm,
In both cases, the height of the protrusion was as low as 2 μm. this is,
The first insulating layers 4, 52 are formed by the metallized wirings 12, 51.
It seems that the effects of the absorption were absorbed. From this,
The effect of providing the insulating portion 20 of the present invention is as follows.
It is also understood that the thickness of the first insulating layer 4 is 0.65 mm or less.

The metallization layer (not shown) on the connection pads 9 of the wiring board 1 and the surface 4a in the cavity 11 is plated with Ni and then with Au plating. On the mounting portion of the IC chip 2 on the surface 4a in the cavity 11 of the plated wiring board 1 on which the plating is applied, an Au-Si-based thin brazing material 22 having a predetermined thickness is placed. After placing the IC chip 2, it is heated to about 400 ° C.
The chip 2 is fixed. Then, the connection pad 9 and the IC
In order to connect the chip 2 via a thin metal wire and finally seal the IC chip 2, a metal or ceramic lid (not shown) is provided so as to cover the entire upper surface of the insulating layer 8 at the uppermost stage of the main body 10.
Are bonded by soldering or the like to form a so-called semiconductor device.

Here, the wiring board 1 of the present invention and the conventional structure,
The gaps in the 50 brazing materials 22, 62 are compared. Three substrates 1 and 50 each having projections having the same height are prepared, and one side is formed on each of the surfaces 4a and 52a under the same conditions as described above.
A 0 mm square IC chip 2 having a thickness of 25 μm and a side of 7 mm square
It was fixed using an Au-Si brazing material preform. Next, the gap S existing in each of the brazing materials 22 and 62 was measured using an ultrasonic exploration imaging apparatus, and the area ratio where the entire gap S was present in each of the brazing materials 22 and 62 was measured as a porosity. The average was calculated. Table 2 shows the results.

[0018]

[Table 2]

From the results shown in Table 2, the porosity was 5 to 10% when the substrate 1 of the present invention was used, whereas the porosity was 35 to 10% when the substrate 50 of the comparative example was used. The former is 50%, about one third to one seventh smaller. From this result, it can be easily understood that when the substrate 1 of the present invention is used, the IC chip 2 can be firmly fixed. Table 2 also shows that the lower the protrusions on the surfaces 4a and 52a of the substrates 1 and 50, the lower the porosity, and the significance and effects of the present invention will be understood from now on. The thickness of the insulating portion 20 made of the insulating paste layer can be adjusted by adjusting the viscosity of the insulating paste, the thickness of the screen mask (or metal mask), and the like.

FIG. 2A is a partially enlarged view of FIG. 1B, and shows the metallized wiring 12 on the upper surface of the second insulating layer 5 and the portion of the insulating portion 20 located between the metallized wiring 12. The thickness of the insulating portion 20 near the top of the metallized wiring 12 is extremely small and is buried. On the other hand, as shown in FIG. 2B, the insulating portion 2 is formed so as to cover the vicinity of the top of the metallized wiring 12 relatively thickly.
By burying the entirety 0, the surface 4a of the first insulating layer 4 can be reliably flattened. However, on the contrary, even if the thickness of the portion of the insulating portion 20 located between the metallized wirings 12 is slightly smaller than the thickness of the metallized wirings 12, the protrusions generated on the surface 4a can be reduced.

As shown in FIG. 2C, an insulating paste is applied only between the metallized wirings 12 and in the vicinity of the wirings 12 (left and right ends in the drawing) to form an insulating part 20. However, similarly, the protrusion can be lowered or eliminated. However, this is disadvantageous in that the printing pattern of the insulating paste becomes complicated and the alignment becomes complicated, but there is an advantage that the amount of the paste used can be saved. Further, when the outer metallized wiring 12 substantially matches the contour of the IC chip mounting portion, as shown in FIG.
The insulating portion 20 may be provided only between the two.

FIG. 3 is a longitudinal sectional view of a wiring board 30 having a different form. A metallized wiring 36 is formed on the lower surface of the same first insulating layer 32 as described above, and an insulating section 40 is formed so as to cover the metallized wiring 36.
Is buried between the first insulating layer 32 and the second insulating layer 34. That is, a conductive paste layer serving as the metallized wiring 36 is formed on the lower surface of the green sheet serving as the first insulating layer 32 by printing, and an insulating paste of the same type of ceramic is printed so as to cover the same. When laminated with another green sheet to be the insulating layer 34, pressed and fired,
The metallized wiring 36 and the insulating portion 40 are connected to the first
Is located between the insulating layer 32 and the second insulating layer 34, and the insulating layers 32 and 34 become the ceramic wiring board 30 integrated with the insulating portion 40. The surface 33a of the first insulating layer 32 in the wiring board 30 is flattened because the insulating portion 40 covers the metallized wiring. Accordingly, when the IC chip 2 is adhered to the metallized layer (not shown) on the surface 33a using the brazing material 22 after the Ni plating and the Au plating are performed, a strong fixed state with few gaps in the brazing material 22 is obtained. Can be.

In each of the above embodiments, a so-called single-chip type wiring board in which one IC chip is mounted on the surface of the board has been described as an example. However, the present invention is not limited to this. is not. That is, the present invention can be applied to a multi-chip module in which a plurality of IC chips are fixedly used.
Semiconductor elements such as ET, capacitors, resistors, inductors,
It is clear that a SAW filter and other electronic components may be mounted on the surface.

Further, an example was shown in which a ceramic comprising alumina as a main component was used as the ceramic constituting the wiring board. However, the present invention is not limited to this.
There is no particular limitation as long as it can constitute a wiring board, such as N), glass ceramic, mullite, and the like. Also, the metallized wiring may be made of a material suitable for the ceramic material to be used. In addition to the exemplified Mo and W, Mo-Mn, Ag, Cu, Ag-Pd, Ag-Pt and other materials May be used.

An example in which an alumina paste similar to a green sheet to be an insulating layer is used as the insulating paste, and thus the insulating portion is mainly composed of alumina, but the insulating paste may be appropriately changed depending on the material of the insulating layer to be used. Just choose. That is, for example, when the insulating layer is made of a ceramic mainly composed of AlN, it is preferable to use a paste mainly composed of AlN as the insulating paste. In consideration of others, it is also possible to use an insulating paste of a material different from that of the insulating layer.

Further, in the above-described embodiment, the case where the IC chip is fixed with the Au-Si brazing material has been described.
The present invention is not limited to this, and Au-Sn, Au-G
e, Pd-Sn-based brazing material (solder material), or a resin-based adhesive such as epoxy resin can be used to fix IC chips and other electronic components. Further, although an example in which a preformed thin plate material is used as the Au-Si brazing material has been described, a paste brazing material (solder material) or a resin-based adhesive may be used.

[0027]

According to the electronic component mounting wiring board of the present invention described above, the electronic component mounting portion on the surface of the first insulating layer has no projections or has only very low projections. Since a special surface can be obtained, even if an electronic component is fixed using a brazing material, the gap in the brazing material can be significantly reduced, and the electronic component can be mounted in a strong and appropriate posture. it can. According to the fourth and seventh aspects of the present invention, the insulating portion and the insulating layer can be formed of the same type of ceramic, and the main body of the substrate itself can be firmly configured. Further, according to the manufacturing method of the sixth aspect, the wiring substrate can be reliably and mass-produced with only a few steps.

[Brief description of the drawings]

FIG. 1A is a perspective view of a wiring board of the present invention on which an IC chip is mounted, and FIG. 1B is a sectional view taken along line BB in FIG.

2A is a partially enlarged view of FIG. 1B, and FIGS.
FIG. 3 is a partially enlarged view of a different form.

FIG. 3 is a longitudinal sectional view showing a different form of the wiring board of the present invention.

4A is a longitudinal sectional view showing a conventional wiring board, and FIG.
It is the elements on larger scale in (A).

[Explanation of symbols]

 1, 30 Wiring board 2 IC chip 4, 32 IC chip 4, 32 First insulating layer 4a, 33a ...... Surface 5, 34 ...... Second insulating layer 6, 7, 8 ... Insulating layer 12, 36 ... Metallized wiring 20, 40 ... ............ Insulation part

Claims (7)

[Claims] 1. A wiring board having a surface for mounting electronic components and having an insulating layer made of a plurality of ceramics and metallized wiring disposed between the insulating layers. Disposed between the first insulating layer and the second insulating layer adjacent thereto and at least near the metallized wirings located immediately below the electronic component mounting portion, between the metallized wirings, or between the metallized wirings A wiring board for mounting electronic components, wherein an insulating portion is buried between wirings or in the vicinity of metallized wirings. 2. The method according to claim 1, wherein the insulating portion is a first metallized wiring.
2. The electronic component mounting wiring board according to claim 1, wherein the wiring board is provided so as to cover either the insulating layer side or the second insulating layer side. 3. The electronic component mounting wiring board according to claim 1, wherein the insulating portion is buried wider than immediately below the electronic component mounting portion on the surface. 4. The wiring board for mounting electronic components according to claim 1, wherein said insulating portion is made of the same type of ceramic as said insulating layer. 5. The method according to claim 1, wherein said first insulating layer has a thickness of 0.01 to 0.6.
The wiring board for mounting electronic components according to any one of claims 1 to 4, wherein the distance is within a range of 5 mm. 6. The method for manufacturing a wiring board according to claim 1, wherein a lower surface of the green sheet serving as the first insulating layer or an upper surface of the green sheet serving as the second insulating layer after firing is provided. After forming a conductive paste layer to be the metallized wiring after firing, an insulating paste is applied so as to substantially cover at least a portion of the conductive paste layer located immediately below the electronic component mounting portion, and the insulating paste is applied thereon. 2. A method for manufacturing a wiring board for mounting electronic components, comprising laminating and firing a second insulating layer or a green sheet to be a first insulating layer. 7. The electronic component according to claim 6, wherein the ceramic material contained in the insulating paste is the same type of ceramic material as the green sheets serving as the first and second insulating layers. Manufacturing method of mounting wiring board.