JPH1117055A - Wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic wiring board in which an electronic-part mounting surface can have a high flatness with less warpage of the board. SOLUTION: A wiring board 1 includes a rectangular frame member 2 of ceramic having a rectangular cavity 6 thereinside and also includes a bottom member 20 of ceramic which forms a bottom of the cavity 6 and has a flat upper face 26 previously polished. The upper face (mounting face) 26 of the bottom member 20 for mounting an IC chip or the like thereon is positioned within an opening 10 in the bottom of the cavity 6. The bottom member 20 is fixedly mounted on the frame member 2 with brazing material disposed therebetween at a periphery 27 of a main body 22 of the bottom member via a brazing material 28. Since the frame 2 and the bottom members 20 have thermal expansion coefficients which are identical or close each other, such a deformation as a warpage in the entire wiring board 1 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic wiring board which requires a high level of flatness on a mounting surface of an electronic component such as an IC chip, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a ceramic multilayer wiring board 150 is used.
6, a main body 152 made of a rectangular ceramic having a plurality of wiring patterns (not shown) built therein,
A cavity 154 formed inside the main body 152
And the step 15 formed along the cavity 154
6. On each step portion 156, a terminal 158 that is electrically connected to the internal wiring pattern is provided, and
4 are connected to the IC chip C and the like mounted on the bottom surface 155 via wires W.

When the chip C is a chip C for converting light into electricity and a large number of chips C are mounted,
Light is applied to each chip C from outside through a glass lid 159 that seals the cavity 154. Since such a chip C receives light from an external light emitting means, it must be accurately arranged at a predetermined position on the bottom surface 155 of the cavity 154. Therefore, cavity 1
For example, the bottom surface 155 has a surface roughness Rmax of about 1
High flatness of 0 μm or less is required. In order to obtain such a flat bottom surface 155, there is a method of performing polishing such as lapping. However, since the step portion 156 along the bottom surface 155 exists integrally, sufficient polishing cannot be performed, and the flatness described above is not achieved. Not obtained. In addition, it is also insufficient to release heat generated from a large number of chips C to the outside of the substrate 150 via the bottom surface 155.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and makes the surface on which electronic components such as IC chips are mounted flat and hardly deforms such as warpage. And a method for manufacturing the same.

[0005]

In order to solve the above-mentioned problems, the present invention has been made by paying attention to forming a wiring board from two components of a ceramic frame member and a bottom member. . In other words, the wiring board of the present invention has a cavity for accommodating an electronic component inside, and forms a ceramic frame member surrounding the cavity, a bottom surface in the cavity, and mounts the electronic component. And a ceramic bottom member having a mounting surface for mounting the electronic component, wherein the surface on which the electronic component is mounted is a flat surface polished in advance.

According to this, the mounting surface (upper surface) of the bottom member is made a flat surface which has been polished in advance, and the frame member and the bottom member are made of ceramics. And the deformation such as warpage of the entire wiring board can be reduced. Therefore, the posture of the electronic component to be mounted can be made accurate and stable for a long time. The frame member and the bottom member have the same or similar thermal expansion coefficients to each other, or include a wiring board made of the same kind of material. According to this, the deformation of the entire wiring board can be eliminated or significantly reduced.

On the other hand, the above-mentioned method for manufacturing a wiring board for obtaining a wiring board includes a step of firing a green sheet to obtain a ceramic frame member having a cavity inside and surrounding the cavity. After firing the sheet, a step of obtaining a ceramic bottom member whose top surface is polished, and a step of fixing the bottom member and the frame member so that the top surface of the bottom member forms the bottom surface of the cavity. , Is included.

According to this, the upper surface (mounting surface) of the bottom member is previously determined.
Can be reliably and easily flattened, and the frame and the bottom member can be tightly integrated with each other to make it difficult to deform the wiring board. For the fixing, brazing with a metal such as silver, welding with a high-melting glass, bonding with a resin such as polyimide, or the like can be used. The steps of obtaining the frame member and the bottom member may be performed completely separately or may be performed simultaneously and in parallel. In short, the steps may be completed immediately before the fixing step.

Further, the frame member and the bottom member may have a coefficient of thermal expansion that is the same as or similar to each other, or may be formed by firing green sheets made of the same kind of material. According to this, since the obtained coefficients of thermal expansion between the frame and the bottom member can be made the same or as close to each other as possible, it is possible to eliminate or significantly reduce the deformation such as the warpage or distortion of the wiring board after the both are fixed. Can be. Therefore, the flatness of the upper surface of the polished ceramic bottom member does not decrease due to warpage after fixing.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a wiring board 1 according to one embodiment of the present invention, and FIG. Wiring board 1
Has a rectangular frame-shaped frame member 2 and a substantially plate-shaped bottom member 20. This frame member 2, as shown in FIG.
It is made of ceramics such as alumina, and has a rectangular cavity 6 formed inside thereof, steps 8 and 9 formed in two steps along the four circumferences thereof, and an opening 10 provided on the bottom surface of the cavity 6. . Further, on each of the step portions 8 and 9, terminals 14 and 16 that are electrically connected to any of the wiring patterns 12 of a plurality of layers formed in the frame member 2 are provided.

Further, on the bottom surface 11 of the frame member 2, a plurality of pins P which are electrically connected to one of the wiring patterns 12 are provided along the longitudinal direction. In addition, a glass lid 18 is fixed to the upper surface 4 of the frame member 2. On the other hand, as shown in FIG. 1 (B), the bottom member 20 includes a flat body 22 made of the same ceramic as described above, and a convex portion 24 protruding from the center of the upper surface thereof. The upper surface (mounting surface) 26 is previously finished to a flat surface by polishing.

Then, the upper surface 26 of the bottom member 20 is positioned in the opening 10 from the bottom surface 11 of the frame member 2,
Further, by melting the eutectic silver brazing material 28 between the periphery 27 of the bottom member 20 and the bottom surface 11 of the frame member 2, the frame / bottom members 2 and 20 are fixed as shown in FIG. . In this state, the upper surface 26 forms the bottom surface of the cavity 6. Next, an IC as an electronic component is placed on the flat upper surface 26 of the bottom member 20.
The chip C is fixedly mounted, and the chip C and the terminals 14 and 16 are soldered via wires W to conduct. In this state, the wiring board 1 can be obtained by fixing the lid 18 to the upper surface 4 of the frame member 2 to seal the inside of the cavity 6 and implanting the pins P on the bottom surface 11 thereof.

According to the wiring board 1, the frame / bottom members 2, 2 made of ceramics having the same or similar thermal expansion coefficients to each other.
The wiring substrate 1 can be prevented from warping due to aging or heat generation of the IC chip C or the like since it is formed by fixing 0.
In addition, since the posture of the chip C and the like mounted on the flat upper surface 26 of the bottom member 20 is accurately maintained as it was at the beginning, for example, the chip C can always accurately receive light from an external light emitting unit. The chip C and the wiring board 1 can perform their original functions. Further, since the upper surface 26 is provided at the upper end of the bottom member 20, it is easy to perform polishing by lapping or the like in advance, and it is possible to perform precise polishing.

Next, a specific method of manufacturing the wiring board 1 will be described with reference to FIG. FIG. 2A shows a plurality of green sheets 30 in the form of a rectangular frame punched into a rectangular shape by pressing the inside.
Are prepared, and the metallized paste 32 is formed on the upper surface of each sheet 30 except for the uppermost sheet 30. This green sheet 30 is made of alumina (Al ₂ O ₃ ),
Silica (SiO ₂ ), ceramic powder such as magnesia (MgO), an organic binder such as butyral or cellulose, and trichlorethylene, butanol, perchlor ethylene as a solvent for these organic binders, known, It was molded by the method. The metallizing paste 32 is made of tungsten (W) or molybdenum (Mo).
Etc., and a predetermined pattern is formed by screen printing. Each sheet 30 is previously filled with a metallized ink for forming a via (not shown) in the pores penetrating the sheet 30.

Next, as shown in FIG. 2 (B), the green sheets 30 are laminated in a predetermined order, heated to about 1500 ° C. while being pressed in the vertical direction in the drawing, and fired while holding for a predetermined time. Then, the frame member 2 which is made of ceramic in which the respective sheets 30 are integrated, has the plurality of wiring patterns 12, the terminals 14, 16 and has the cavity 6, the step 8, 9 and the opening 10 formed therein is obtained. On the other hand, a plate-like green sheet having a cross-sectional shape shown in FIG.
A ceramic bottom member 20 is obtained. The upper surface 2 of the convex portion 24 protruding from the center of the bottom member 20 excluding the front and rear ends as shown.
6 is polished by, for example, lapping using carbon random. The flatness of the upper surface 26 after such polishing is, for example, 10 μm or less in Rmax or 10 μm or less in the thickness direction with respect to the virtual reference plane. Incidentally, the flatness of the mounting surface of a general chip C is about 50 at Rmax.
It is about μm. In order to provide the upper surface 26 with a high degree of flatness, it is more reliable and easier to polish the upper surface 26 after polishing the bottom surface 23 of the main body 22 of the bottom member 20 in the same manner as described above.

Then, as shown in FIG. 2D, for example, a eutectic silver
With the brazing material 28 placed thereon and heated to about 850 ° C.,
As shown, the wiring board 1 can be obtained by pressing the bottom surface 11 of the frame member 2 and fixing the frame / bottom members 2 and 20. Thereafter, as described above, mounting of the chip C, bonding of the wire W, sealing with the lid 18, and
Is planted. According to this manufacturing method, since the upper surface 26 of the ceramic bottom member 20 is polished in advance, it is possible to perform polishing with higher precision as compared with a conventional wiring board, and to perform frame /
Since the bottom members 2 and 20 are made of the same alumina ceramic, the fixing can be easily and firmly performed, and the subsequent thermal deformation is the same, so that warpage and the like can be prevented.

Incidentally, the bottom member 20 may be formed by a method in which a plurality of green sheets are laminated and then fired. In this case, a uniform metallized layer is previously formed on the entire surface or a part between the sheets as described later. If it is formed, it can contribute to promoting heat radiation from the IC chip C or the like mounted on the upper surface 26 after the wiring board 1 is formed. Alternatively, the frame member 2 may be formed by firing from a single green sheet, and the cavity 6 may have no step on the side thereof. Further, the frame member 2
A plurality of metallizations having an inverted L-shaped cross section are partially formed in advance across the bottom surface 11 and the side surface of the bottom member 20 to provide terminals for connecting the wiring board 1 to a motherboard such as a printed board. It is also possible to form. Thereby, a meniscus of solder or the like brazed to the terminal can be easily visually confirmed.

FIG. 3 is a schematic sectional view showing a wiring board of a different form. FIG. 3A shows a cavity 34 having an opening 36 at the bottom as described above, and a step 35 along the cavity 34.
And a wiring board 40 having a rectangular frame-shaped frame member 33 having a flat bottom member 37. The frame / bottom members 33 and 37 are made of the same type of ceramic, and the upper surface 38 of the bottom member 37 is polished flat in advance. The frame / bottom members 33 and 37 are fixed to each other via a brazing material 39 placed around the upper surface 38. As a result, the upper surface 38 is located at the bottom surface of the opening 36 and mounts an IC chip or the like (not shown).

According to the wiring board 40, since the flat bottom member 37 is used, the upper surface 38 can be polished more easily and accurately, and the cost of processing and polishing the bottom member 37 can be reduced. Further, since the upper surface 38 of the bottom member 37 also serves as a joint surface between the mounting surface of the IC chip or the like and the frame member 33, the joint surface with the frame member 33 is polished at the same time as the mounting surface is polished, so that a tighter fixing is achieved. It can be performed. It should be noted that a terminal (not shown) is formed on the step 35 in the same manner as described above.

FIG. 3B also shows a cavity 43 having an opening 44 at the bottom, a frame member 42 having a step 45 along the cavity 43, a substantially flat cross section, and a shallow recess along the bottom side. Wiring board 50 having bottom member 46 provided with groove 47
Is shown. The frame / bottom members 42, 46 are made of the same type of ceramic, and the upper surface 48 of the bottom member 46 is polished flat in advance. At the periphery of the upper surface 48, the frame / bottom members 42 and 46 are fixed to each other via a brazing material 49. The upper surface 48 is located on the bottom surface of the opening 44,
A C chip and the like are mounted. According to this wiring board 50,
Since the concave groove 47 is provided on the opposite side of the upper surface 48 of the bottom member 46, the thickness thereof can be reduced, and heat from a chip or the like mounted on the upper surface 48 can be easily released to the outside.

FIG. 3C shows a further different wiring board 60. The frame member 51 has a cavity 52 having an opening 53 as described above, and a step 54 along the cavity 52. On the other hand, the bottom member 55 includes two large and small flat plates 56 and 57.
The frame / bottom members 51 and 55 are made of the same type of ceramic, and the upper surface 58 of the flat plate 57 above the bottom member 55 is polished flat beforehand and fixed to the lower flat plate 56 by brazing or the like. The frame / bottom members 51 and 55 are fixed to each other around the lower flat plate 56 via a brazing material 59, and the upper surface 58 is located near the substantially opening 53 of the cavity 52. According to the wiring board 60, since the bottom member 55 is composed of the two flat plates 56 and 57 and the upper surface of the latter is narrow, the polishing applied thereto can be performed easily and quickly.

FIG. 3D also shows a different wiring board 70. The frame member 61 has a cavity 62 having an opening 63 at the bottom similarly to the above, and steps 64 and 65 along the cavity 62. On the other hand, the bottom member 66 has a flat top surface 68 that has been polished in advance.
And is mounted on the lower step 65 over four steps around the step 65 and fixed to the frame member 61 by the brazing material 69. Both the frame and bottom members 61 and 66 are made of the same type of ceramic. The upper surface 68 of the bottom member 66 is
2 is located near the opening 63. This wiring board 70
According to this, since a thin flat plate is used for the bottom member 66, the upper surface 68 thereof can be easily polished and the wall thickness can be reduced as much as possible. Therefore, an IC chip or the like mounted on the upper surface 68 can be accurately arranged, and heat generated from the chip can be easily released.

FIG. 4 is a schematic cross-sectional view of a wiring board of still another embodiment. FIG. 4A shows a rectangular frame member 72 and a bottom member 76 fixed on a bottom surface 75 of a cavity 73 thereof.
Is shown. Frame / bottom members 72, 76
The frame member 72 has a step 74 along the cavity 73, and the bottom surface 77 of the bottom member 76 is fixed on the bottom surface 75 via the brazing material 79. The upper surface 78 of the bottom member 76 is polished in advance and is located in the cavity 73. According to such a wiring board 80, only the upper surface 78 of the bottom member 76 made of a narrow flat plate needs to be polished, and since the range in which the brazing material 79 is provided is narrow, both polishing and fixing become easy, and These costs can be reduced. By making the bottom member 76 as thin as possible, an IC chip or the like mounted on the upper surface 78 can be accommodated in the cavity 73, and a decrease in heat dissipation can be suppressed.

FIG. 4B relates to a wiring board 90 of another embodiment. This substrate 90 is made of a frame member 8 made of the same type of ceramic.
1 and a bottom member 86. The frame member 81 has a stepped portion 84 along the inner cavity 82 and an opening 83 at the bottom thereof.
Has a wide concave portion 85 on the bottom surface side. Also, the bottom member 8
6 has a shallow concave groove 87 on the bottom surface side, and its upper surface 88 is previously planarized by polishing. When the brazing material 89 is placed around the upper surface 88 of the bottom member 86 and the bottom member 86 is inserted into the recess 85 of the frame member 81 and fixed as shown in FIG. A wiring board 90 on which the upper surface 88 of the bottom member 86 is located is obtained. According to the substrate 90, since the bottom member 86 is substantially inserted into the concave portion 85, the volume in the cavity 83 can be easily secured, and the bottom member 86 can also be thinned. Heat can be easily released to the outside.

FIG. 4C relates to a wiring board 100 of still another embodiment. This substrate 100 has a frame member 91 and a bottom member 95 made of the same type of ceramic. The frame member 91 has a step 94 along the inner cavity 92 and an opening 9 at the bottom thereof.
And 3. The bottom member 95 has a shallow groove 9 on the bottom surface side.
6, a continuous serrated uneven portion 97 provided on the ceiling surface of the concave groove 96, and an upper surface 98 polished flat. Then, the frame / bottom members 91 and 95 are fixed via the brazing material 99 placed around the upper surface 98 to form the substrate 100. According to the substrate 100, since the concave and convex stripes 97 are further formed in the concave groove 96 of the bottom member 95, heat generated from an IC chip or the like mounted on the upper surface 98 is easily released to the outside.

FIG. 4D relates to a separate type of wiring board 110. This substrate 110 also has a frame member 101 and a bottom member 105 made of the same type of ceramic. The frame member 101 has a step 104 along the inner cavity 102 and an opening 103 at the bottom thereof. The flat bottom member 10
5 has an upper surface 106 which is planarized by polishing, and has a plurality of metallized layers 108 built therein.
Then, the frame / bottom members 101 and 105 are fixed via the brazing material 109 placed around the upper surface 106 to form the substrate 110. According to such a wiring board 110, heat generated by an IC chip or the like mounted on the upper surface 106 can be easily released to the outside via the metallized layer 108 in the bottom member 105. The metallization layer 108 may be formed substantially entirely in the left-right direction of the bottom member 105, or may be a net pattern having continuous through holes (not shown) at regular intervals. Also,
By forming vias that conduct between the metallization layers 108 and the upper surface 106 at appropriate positions, it is possible to further enhance the heat dissipation.

FIG. 5 relates to a wiring board different from the above-described embodiment. Wiring board 120 shown in FIG.
Has a frame member 111 having a square cavity 112 in a plan view and a square bottom member 115 fixed thereto. The frame / bottom members 111 and 115 are also made of the same type of ceramic. The frame member 111 has a step 113 along the cavity 112 and a square opening 114 at the bottom, and a terminal (not shown) is formed on the step 113. on the other hand,
As shown in FIG. 5 (B), the bottom member 115 is located at the central convex portion 1.
The peripheral surface 116 is fixed to the bottom surface of the frame member 111 by brazing so that the polished square upper surface 118 at 17 is located within the opening 114.
According to the wiring board 120, since the cavity 112 and the upper surface 118 form a square, it is easy to accurately arrange a single square IC chip or the like and many chips in the vertical and horizontal directions.

The wiring board 130 shown in FIG.
It has a frame member 121 having a cavity 122 having a substantially octagonal shape in a plan view inside, and a square bottom member 125 fixed to the frame member 121. The frame / bottom members 121, 125 are made of the same type of ceramic. The frame member 121 has the cavity 1
Step 22 along 22 and octagonal opening 124 at the bottom
And a terminal (not shown) is formed on the step portion 123. On the other hand, as shown in FIG. 5B, the bottom member 125 is a polished octagonal upper surface 1 at the central projection 127.
28 is fixed to the bottom surface of the frame member 121 at the periphery 126 by brazing so that the opening 28 is located in the opening 124.

Further, the wiring board 140 shown in FIG.
Frame member 13 having substantially circular cavity 132 in plan view
1 and a square bottom member 135 fixed thereto, and the frame / bottom members 131 and 135 are made of the same type of ceramic. The frame member 131 is formed along the cavity 132 with the stepped portion 1.
33 and a substantially circular opening 134 at the bottom, and a terminal (not shown) is formed on the step 133. On the other hand, FIG.
As shown in the figure, the bottom member 135 is formed such that the polished substantially circular upper surface 138 of the central convex portion 137 has the above-mentioned opening 13.
4 and is fixed to the bottom surface of the frame member 131 at its periphery 136 by brazing. According to these wiring boards 130 and 140, each cavity 12
2, 132 and the upper surfaces 128, 138 have an octagonal shape or a circular shape, so that it is easy to arrange an IC chip or the like or a large number of chips having the same external shape in the radial direction or the spiral direction. Incidentally, the flat upper surface for mounting the IC chip or the like forming the cavity or the bottom surface thereof can be formed in a polygonal shape, an elliptical shape, or the like other than the above in plan view.

The present invention is not limited to the embodiments described above. For example, the ceramic of the frame / bottom member is not limited to the alumina, and a glass ceramic such as aluminum nitride, mullite, cordierite or the like can be used. In this case, it is necessary to use the same ceramic for the frame and the bottom member or to apply the same or different ceramics having the same or similar coefficient of thermal expansion in order to prevent deformation.
Further, for example, the bottom member 37 shown in FIG. 3A is formed by further fixing the same ceramic in the form of a rectangular frame around the polished upper surface 38, and the upper surface 38 on which an IC chip or the like is mounted is formed.
Can be made even lower to form a relatively deep cavity 34.

Further, the present invention provides a so-called pin grid array type or leadless chip carrier having the cavity,
The present invention can also be applied to a wiring board such as a multichip module.
Also, a flat upper surface located in the cavity has I
Not limited to the C chip, semiconductor elements such as transistors and EFTs, and electronic components such as capacitors, inductances, resistors, and SAW filters can also be mounted. The material of the terminal and the wiring pattern of the frame member is not limited to W and Mo, but may be Mo-Mn, Cu, Ag, Ag-Pd, Ag-P.
It is also possible to apply t or the like. It is also possible to provide a terminal such as a solder bump, a lead, or a pad instead of the pin implanted on the bottom surface of the frame member.

[0032]

According to the wiring board of the present invention described above, both the frame and the bottom member are made of ceramic, and the upper surface of the bottom member is highly planarized in advance by polishing. The mounted IC chip and the like can be fixed in an accurate posture. In addition, since the frame and the bottom member change similarly even under the influence of heat, it is possible to eliminate or significantly reduce deformation such as warping or distortion of the entire wiring board. Therefore, it is possible to maintain the chip and the like mounted on the upper surface for a long period of time with the intended accurate placement posture. Further, according to the manufacturing method of the present invention, the wiring board as described above can be provided reliably and easily, and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1A is a perspective view of a wiring board according to the present invention, and FIG.
The BB sectional drawing in a middle.

FIGS. 2A to 2D are schematic cross-sectional views illustrating steps for manufacturing a wiring board according to the present invention.

FIGS. 3A to 3D are schematic cross-sectional views of different types of wiring boards.

FIGS. 4A to 4D are schematic cross-sectional views of wiring boards of still different forms.

FIGS. 5A, 5C, and 5D are perspective views of another type of wiring board;
(B) is a BB sectional view in these.

FIG. 6 is a sectional view showing a conventional wiring board.

[Explanation of symbols]

1,40,50,60,70,80,90,100,110,120,130,1
40 ...... Wiring board 2, 33, 42, 51, 61, 72, 81, 91, 101, 111, 121,
131 ... Frame member 6, 34, 43, 52, 62, 73, 82, 92, 102, 112, 122, 1
32 …… Cavities 10,36,44,53,63,83,93,103,114,124,134
............ Opening 20,37,46,55,66,76,86,95,105,115,125,
135 Bottom member 26, 38, 48, 58, 68, 78, 88, 98, 106, 118, 1
28,138… Upper surface (mounting surface) 30 …………………………………………………
……… Green sheet

Claims (4)

[Claims] 1. A ceramic frame member having a cavity for accommodating an electronic component therein and surrounding the cavity, and a mounting surface forming a bottom surface in the cavity and mounting the electronic component. A wiring board comprising: a ceramic bottom member; and a surface on which the electronic component is mounted is a flat surface polished in advance. 2. The wiring board according to claim 1, wherein the frame member and the bottom member have the same or similar coefficient of thermal expansion as one another, or are made of the same kind of material. 3. A step of sintering the green sheet to obtain a ceramic frame member having a cavity inside and surrounding the cavity; and sintering the green sheet and polishing the upper surface of the green sheet to form a ceramic bottom part. A method for manufacturing a wiring board, comprising: a step of obtaining a material; and a step of fixing the bottom member and a frame member such that an upper surface of the bottom member forms a bottom surface of the cavity. 4. The method according to claim 3, wherein the frame member and the bottom member have the same or similar thermal expansion coefficients to each other, or are formed by firing green sheets made of the same material. Method of manufacturing a wiring board.