JP2004055991A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board in which a via conductor can be easily arranged at the corner of an insulating layer having a cavity whose inside should be mounted with an electronic component. <P>SOLUTION: This wiring board 1 is provided with a plurality of insulating layers 2 to 5 showing almost rectangles from the point of view of flatness, wiring layers 20 formed on surfaces 2a to 5a of the insulating layers 2 to 5, and a cavity 6 formed inside the insulating layers 2 to 4 from the point of view of flatness. In the insulating layer 2 in the uppermost layer, a diameter R of a curvature 7a applied to the internal corner of the cavity 6 adjacent to the corner through which the via conductor V is put is set so as to be larger than a diameter (r) of the curvature 7b applied to the internal corner of the cavity 6 adjacent to the corner through which the via conductor V is not put. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board having a cavity in which an electronic component such as a crystal unit is mounted inside.
[0002]
[Prior art]
The wiring board 50 shown in FIGS. 7A and 7B has a plurality of insulating layers 51 to 54 made of ceramic or the like, a wiring layer (not shown) formed on the surface and between the layers, and a layer other than the lowermost insulating layer 54. And a cavity 55 formed inside the insulating layers 51 to 53 in plan view. As shown in FIGS. 7A and 7B, the opening 56 of the cavity 55 in the uppermost insulating layer 51 has openings 57, 58 of the cavity 55 in the insulating layers 52, 53 in the vertical direction. The surface 52a of the second insulating layer 52 is exposed above and below the opening 57 as a horizontally long step.
[0003]
The four corners of the opening 56 are provided with a radius 59 having the same radius R. The surface 54a of the insulating layer 54 is exposed at the bottom of the cavity 55.
Further, as shown in FIGS. 7A and 7B, a quarter circular curved surface 60 having the same radius r is continuously formed in the four corners of the insulating layers 51 to 54 in the vertical direction. Formed. Among these, a curved conductor 62 is formed on the curved surface 60 of the lowermost insulating layer 54, and is connected to a wiring layer (not shown) formed on the surface 54 a of the insulating layer 54. Conduction is made to the terminal located on the bottom surface of the not-shown quartz oscillator or SAW filter mounted in the cavity 55 through the cavity.
[0004]
Further, as shown in FIGS. 7 (A) and 7 (B), a concave groove 64 having a semicircular cross section in plan view and a concave groove conductor 66 covering them are provided between the upper and lower sides of the insulating layers 52 to 54 facing each other. Are formed respectively. These are connected to wiring layers (not shown) formed on the surfaces 52a and the like of the insulating layers 52 and 53, and the upper surface of the SAW filter and the like mounted in the cavity 55 via these wiring layers and wires (not shown). Is electrically connected to the terminal located at.
As shown in FIGS. 7A and 7B, a plurality of via conductors V are sandwiched between the radius 59 of the opening 56 and the curved surface 60 at diagonal corners of the insulating layers 51 to 53. And it is formed continuously in the vertical direction. The via conductor V connects between wiring layers located on the surfaces 51a, 52a, 54a and the like of the insulating layers 51 to 54.
[0005]
[Problems to be solved by the invention]
By the way, due to the recent demand for miniaturization of the wiring board, the outer shape of the insulating layer 51 and the like is made smaller than before, while the size of the electronic component to be mounted does not change much. Same as before. As a result, the width W of each corner in the uppermost insulating layer 51 is reduced, so that it is difficult to penetrate the via conductor V and the via hole for forming the via conductor V in the corner.
The present invention solves the problems in the conventional technique described above, and provides a wiring board that can easily arrange via conductors in corners of an insulating layer having a cavity for mounting electronic components inside. Make it an issue.
[0006]
[Means for Solving the Problems]
The present invention relates to a method of measuring the radius of the inner corner of the cavity and the radius of the quarter-curved concave portion at the outer corner of the uppermost insulating layer between the corner where the via conductor penetrates and the corner where the via conductor does not penetrate. It is made with the idea of making the difference.
That is, the first wiring board of the present invention (claim 1) includes a plurality of insulating layers having a substantially rectangular shape in a plan view, and a wiring layer formed on at least one of the surfaces and the layers of the plurality of insulating layers. A cavity formed at least inside the uppermost insulating layer in a plan view, and in the uppermost insulating layer, an inner corner of the cavity near a corner through which a via conductor penetrates. The diameter is larger than the diameter of a radius provided at an inner corner of the cavity close to a corner through which the via conductor does not penetrate.
[0007]
According to this, at the corner through which the via conductor penetrates in the insulating layer, the radius of the radius at the inner corner of the cavity is larger than the radius of the radius at the inner corner of the cavity of the corner through which the via conductor does not penetrate. You. For this reason, at the corner through which the via conductor penetrates, the width of the insulating layer at such a corner becomes larger than the width of the insulating layer at the corner where the via conductor does not penetrate. As a result, a wiring board in which via holes and via conductors are easily arranged in such a wide corner can be obtained. Therefore, the via conductor does not approach or be exposed to the outside of the insulating layer, and the conduction between the wiring layers formed on the surfaces of the plurality of insulating layers and between the layers can be ensured.
Note that the insulating layer includes a resin insulating layer in addition to the ceramic insulating layer.
[0008]
On the other hand, a second wiring board (Claim 2) of the present invention includes a plurality of insulating layers having a substantially rectangular shape in a plan view, and a wiring layer formed on at least one of the surfaces and the layers of the plurality of insulating layers. A cavity formed at least inside the uppermost insulating layer in plan view, wherein the uppermost insulating layer has an arc-shaped cross section provided at a protruding corner of a corner through which a via conductor passes. The diameter of the portion is smaller than the diameter of a concave portion having an arc-shaped cross section provided at a protruding corner of a corner through which the via conductor does not penetrate.
According to this, in the corner through which the via conductor penetrates in the insulating layer, the diameter of the concave portion of the circular cross section provided at the protruding corner is smaller than the cross sectional arc provided at the protruding corner of the corner through which the via conductor does not penetrate. The diameter of the concave portion of the shape is made smaller. This also makes the width of the insulating layer at the corner where the via conductor penetrates larger than the width of the insulating layer at the corner where the via conductor does not penetrate. Therefore, it is possible to provide a wiring board in which via conductors are easily arranged in such a wide corner.
[0009]
The wiring board according to the present invention includes a plurality of insulating layers having a substantially rectangular shape in a plan view, a wiring layer formed on at least one of the surfaces and interlayers of the plurality of insulating layers, and at least the uppermost insulating layer. A cavity formed inside the layer in a plan view, wherein, in the uppermost insulating layer, a radius of an inner corner of the cavity adjacent to a corner through which the via conductor penetrates, The diameter is larger than the radius of the radius provided at the inner corner of the cavity adjacent to the corner that does not penetrate, and an arc-shaped recess provided at the outer corner of the corner through which the via conductor penetrates in the uppermost insulating layer. The diameter of the shaped conductor may be smaller than the diameter of the concave conductor having an arc-shaped cross section provided at the corner of the corner where the via conductor does not penetrate.
According to this, at the corner through which the via conductor penetrates in the insulating layer, the radius of the radius provided at the inner corner of the cavity is increased, or the arc-shaped concave portion provided at the outer corner of the corner is formed. The diameter is reduced. In particular, in the corner of the insulating layer in which the radius of the radius provided at the inner corner of the cavity is increased and the diameter of the concave portion having an arc-shaped cross section provided at the protruding corner is reduced, the width can be further increased. Become.
[0010]
The present invention also provides a plurality of insulating layers having a substantially rectangular shape in a plan view, a wiring layer formed on at least one of the surfaces and the interlayers of the plurality of insulating layers, and at least an uppermost insulating layer in a plan view. And a cavity formed on the inside, the method for manufacturing a wiring board comprising: a plurality of product areas to be the uppermost insulating layer in the insulating sheet having a plurality of product area corners in the sheet. Circular through-holes are formed in adjacent T-shaped or cross-shaped boundaries, and cut in each product area to form a semicircular concave portion or a quarter circular concave portion. It is also possible to include the method for manufacturing a wiring board according to claims 1 and 2 including the steps.
In this case, in the insulating sheet serving as the uppermost insulating layer in the plurality of wiring boards, the concave portion forming the concave conductor having the arc-shaped cross section can be efficiently manufactured with a small number of steps. Therefore, it is possible to reliably and inexpensively provide a wiring board having a cavity for mounting an electronic component while meeting a demand for miniaturization.
The insulating sheet includes a green sheet mainly made of ceramics and a resin sheet made of synthetic resin.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1A is a plan view showing a plurality of insulating layers 2 to 5 and a cavity 6 formed inside the insulating layers 2 to 5 in the first wiring board 1 according to the present invention, and FIGS. FIG. 3 is a cross-sectional view taken along line BB or CC in FIG.
As shown in FIGS. 1 (A) to 1 (C), the wiring board 1 includes insulating layers 2 to 5 having a thickness of several 100 μm, which are made of, for example, a ceramic containing alumina as a main component and have a square (rectangular) shape in plan view. A substantially rectangular cavity 6 in plan view is located inside the insulating layers 2 to 4 except for the lowermost insulating layer 5 which are stacked. On the surfaces 2a to 5a of the insulating layers 2 to 4, a wiring layer described later is formed.
[0012]
As shown in FIGS. 1A and 1C, the opening 7 of the cavity 6 in the uppermost insulating layer 2 has a width in the vertical direction that is larger than the opening 8 of the cavity 6 in the insulating layers 3 and 4. The surface 3a of the second insulating layer 3 is exposed above and below the opening 7 as a horizontally long step. However, as shown in FIGS. 1A and 1B, the opening 7 of the cavity 6 in the uppermost insulating layer 2 has an opening 8 Is the same as The surface 5 a of the insulating layer 5 is exposed at the bottom of the cavity 6. An electronic component 18 such as a quartz oscillator or a SAW filter is mounted in the cavity 6.
[0013]
As shown in FIG. 1A, arc-shaped concave portions 10 each having a quarter-circular cross section in a plan view are continuously formed at four protruding corners of the insulating layers 2 to 5 in the vertical direction. A concave conductor 12 to be described later is formed in the concave portion 10 of the lowermost insulating layer 5 among them. As shown in FIG. 1 (A), in the middle of the upper and lower sides facing each other in the insulating layers 3 to 5, a concave groove 14 having a substantially semicircular cross section in plan view and a concave conductor Are formed respectively. The concave conductors 12, 16 are made of, for example, W, Mo, Ni, Ag, or Pd, or a sintered body of an alloy based on any of these.
[0014]
As shown in FIG. 1A, in the uppermost insulating layer 2, a via conductor V having a diameter of about 100 μm is formed through each of the lower left corner and the upper right corner, and the via conductor V is formed on the lower side. The insulating layers 3 and 4 are continuously penetrated in the vertical direction. The via conductor V is also a sintered body made of the same metal or alloy as described above.
In the uppermost insulating layer 2, the radius (diameter) R of the radius 7a attached to the inner corner of the opening 7 of the cavity 6 close to the corner through which the via conductor V penetrates is close to the corner through which the via conductor V does not penetrate. The radius (diameter) r of the radius 7b provided at the inner corner of the opening 7 of the cavity 6 is set to be larger. Incidentally, when the opening 7 of the cavity 6 in the insulating layer 2 is 3.0 mm × 3.0 mm, the radius R is 0.4 to 0.6 mm and the radius r is 0.15 to 0.25 mm. Therefore, in the insulating layer 2, the width of each of the lower left and upper right corners through which the via conductor V penetrates is larger than the width of each of the upper left and lower right corners through which the via conductor V does not penetrate. Therefore, the via conductor V can be accurately and reliably penetrated through such a corner.
[0015]
FIG. 2 is a perspective view of the insulating layers 2 to 5 forming the wiring board 1. As shown in FIG. 2, the uppermost insulating layer 2 has a ground wiring layer 20 entirely covering the entire surface 2a surrounding the opening 7 of the cavity 6. The wiring layer 20 functions not only as a ground circuit but also for mounting a metal frame (not shown) having a square shape in a plan view thereon after mounting the electronic component 18 in the cavity 6. By sealing the opening of the metal frame with a cover plate (not shown), the mounted electronic component 18 can be sealed. Also, via conductors V, V at diagonal positions are connected to the wiring layer 20.
The metal frame may be omitted, and a cover plate may be directly brazed to the wiring layer 20. The wiring layer 20 and each of the following wiring layers are also sintered bodies of the metal or alloy.
As shown in FIG. 2, the insulating layers 3 and 4 of the second and third layers are provided on the surfaces 3a and 4a around the opening 8 of the cavity 6 on the signal wiring layers 21 to 28 having a predetermined pattern. 31 to 38 are formed. Of these, the wiring layers 23, 26, 33, 36 are individually connected to the adjacent concave conductors 16 on the outside thereof.
[0016]
Via conductors V, V similar to those described above penetrate through the corners of the insulating layers 3, 4 at diagonal positions. Among these, the via conductor V penetrating the insulating layer 3 connects the wiring layer 20 to the wiring layers 34 and 35, and the via conductor V penetrating the insulating layer 4 is the wiring layer 34 and 35 The connection portion 42 of the layer 40 is connected.
As shown in FIG. 2, near the center of the surface 5a of the lowermost insulating layer 5, a wiring layer 40 for power supply having a substantially rectangular shape in a plan view is formed in a solid shape. The connection portions 42 that are individually connected to the concave conductors 12 located at the four protruding corners are formed radially. A terminal located on the bottom surface of the electronic component 18 is connected to the solid wiring layer 40 via a brazing material (not shown).
[0017]
The wiring board 1 is manufactured through the following steps.
First, as shown in FIG. 3A, a plurality of green sheets (insulating sheets) S containing, for example, alumina as a main component and containing an organic binder are prepared. A broken line in the green sheet S indicates a cutting line for subsequent cutting, and one green sheet S has four product areas s to be the insulating layers 2 in succession.
Next, as shown in FIG. 3 (B), a circular through-hole h having a dedicated diameter for each part is formed on a T-shaped boundary or a cross-shaped boundary between a plurality of adjacent product areas s, s by a laser. Drilled by machining or mechanical punch.
Next, as shown in FIG. 3C, a via hole vh having a diameter of about 100 μm is formed at a predetermined position in each of the plurality of product areas s by the same method as described above.
[0018]
Further, as shown in FIG. 3 (D), a position near the center in each of the plurality of product areas s, s is punched by a punching die having a predetermined cross-sectional shape, so that an opening that becomes a part of the cavity 6 is formed. The part 7 is formed. At this time, a punching die is used in which the radiuses 7a and 7b having the radius R and the radius r are formed in the inner corners of the opening 7.
Next, after filling the via hole vh with a conductive paste containing a metal powder such as W by mask printing, a similar paste is formed on the entire surface of the product area s by screen printing. As a result, the via conductor V is formed in the via hole vh, and the wiring layer 20 is formed on the surface of each product area s.
Then, by cutting the green sheet S along the broken line, four green sheets S2 for the uppermost insulating layer 2 are obtained as shown in FIG. At this time, the through hole h becomes a quarter circular concave portion 10 at the four corners of the sheet S2, or a semicircular concave portion 14 located at the middle of the upper and lower sides of the sheet S2.
[0019]
The green sheets S3, 4S for the insulating layers 3, 4 are also formed in the same manner as in the method shown in FIGS. Note that a conductive paste is also formed on the inner wall of the through hole h which becomes the concave portion 14 of the sheets S3 and 4S.
Further, the lowermost green sheet S5 for the insulating layer 5 is formed by forming a circular through hole h in the green sheet S, forming a conductive paste on the surface of the green sheet S by screen printing, and then forming the solid paste by the broken line. It is obtained by cutting along. Note that the conductive paste is also formed on the inner walls of the concave portions 10 and 14 of the sheet S5.
Then, as shown in FIGS. 4A to 4C, the green sheets S2 to S5 are laminated while being pressed, and then inserted into a firing furnace (not shown) at 800 to 1400 ° C. for about 0.5 to 6 hours. Heat and bake. As a result, as shown in FIG. 1A and FIGS. 4A to 4C, the wiring substrate 1 can be efficiently and reliably obtained.
[0020]
FIGS. 5A and 5B relate to a second wiring board 1a according to the present invention. In the following, common reference numerals are used for parts and elements common to the above-described embodiment.
As shown in FIGS. 5A and 5B, the wiring board 1a is also formed by laminating insulating layers 2 to 5, and inside the insulating layers 2 to 4 except for the lowermost insulating layer 5, the same cavity as described above. 6 is located. The wiring layers 20 and the like are formed on the surfaces 2a to 5a of the insulating layers 2 to 4 in the same manner as described above. As shown in FIG. 5A, in the uppermost insulating layer 2, an arc-shaped recess having a cross section of a quarter circle provided at each of the lower left corner and the upper right corner of each of the corners through which the via conductor V passes. The radius (diameter) d of the shape portion 11 is smaller than the radius (diameter) D of the concave portion 10 provided at each of the upper left and lower right corners where the via conductor V does not penetrate.
Incidentally, when the size of the opening 7 of the cavity 6 in the uppermost insulating layer 2 is 3.0 mm × 3.0 mm, the radius d is 0.15 to 0.25 mm and the radius D is 0.3 to 0. 0.4 mm.
[0021]
That is, in the wiring board 1a, as shown in FIG. 5 (A), all four inner corners of the opening 7 of the cavity 6 in the uppermost insulating layer 2 are reduced to radius 7b of radius r, By reducing the radius d of the concave portion 11 provided at the corner of the corner through which the conductor V passes, a wide width at the corner can be secured. Therefore, the via conductor V can be accurately and reliably penetrated.
In addition, according to the wiring board 1a, since the opening 7 of the cavity 6 can be widened, the area of the wiring layers 21 to 28 exposed on the surface 2a of the second insulating layer 2 can be secured. As a result, the bonding operation of the wires connecting the signal wiring layers 21 to 28 and the terminals located on the upper surface of the electronic component mounted in the cavity 6 becomes easy.
[0022]
FIGS. 6A and 6B relate to a wiring board 1b in an application form of the wiring boards 1 and 1a.
As shown in FIGS. 6A and 6B, the wiring board 1b is formed by laminating insulating layers 2 to 5 and inside the insulating layers 2 to 4 except for the lowermost insulating layer 5, the same cavity as described above. 6 is located. On the surfaces 2a to 5a of the insulating layers 2 to 4, wiring layers 20, 40 and the like are formed in the same manner as described above.
As shown in FIG. 6A, in the uppermost insulating layer 2, the radius of the radius 7a provided at the inner corner of the opening 7 of the cavity 6 near the lower left and upper right corners through which the via conductor V passes. R is larger than the radius r of the radius 7b provided at the inner corner of the opening 7 of the cavity 6 near the corner through which the via conductor V does not penetrate as described above.
[0023]
At the same time, the radius d of the arc-shaped concave portion 11 having a cross section of a quarter circle provided at the protruding corners of the lower left and upper right corners through which the via conductor V penetrates, The radius D of the concave portion 10 provided at each of the lower right corners is formed in the same manner as described above.
That is, in the wiring board 1b, as shown in FIG. 6A, in the uppermost insulating layer 2, the radius R of the inner corner of the cavity 6 close to the corner through which the via conductor V passes is increased and the same. By reducing the radius d of the concave portion 11 provided at the corner of the corner, the width at the corner can be further increased. Therefore, in the corner, the via conductor V can be easily and reliably penetrated, and conduction of the upper and lower wiring layers 20 and the like can be ensured. In the above-described corner of the wiring board 1b, two via conductors V can be penetrated in parallel.
[0024]
The present invention is not limited to the embodiments described above.
The corners through which the via conductors V penetrate are not limited to corners at diagonal positions in the insulating layer 2 but may be arranged at corners at both ends of the same side or at three corners.
The radius R, r, d, D of the radius 7a, 7b provided at the inner corner of the cavity 6 or the concave portion 10, 11 provided at the protruding corner of the insulating layer 2 is a constant drawing a quarter circle. Not only the value but also a variable value that draws a flat quarter ellipse can be used.
Further, ceramics such as barium titanate, mullite, aluminum nitride, glass ceramic, and low-temperature fired ceramic may be applied to the insulating layers 2 to 5 in addition to alumina.
[0025]
Alternatively, for the insulating layers 2 to 5, a synthetic material such as epoxy, polyester, polyimide, bismaleimide / triazine, or a composite material containing an inorganic filler such as glass filler or glass cloth or an inorganic fiber is applied. May be. When the insulating layers 2 to 5 made of such a resin or a composite material are used, the concave conductors 12 and 16 and the via conductor V such as the wiring layer 20 are formed by using, for example, copper plating or a wiring pattern. For this purpose, a known photolithography technique is used. Further, the insulating layers 2 to 5 made of the above resin or the like are formed into a predetermined shape by press working including punching, and then laminated via an adhesive.
In addition, the electronic components mounted in the cavity 6 are not limited to the crystal resonator and the SAW filter, but passive components such as a chip capacitor, a chip inductor, a resistor, and a filter, a transistor, a semiconductor element, an FET, a low noise amplifier ( Active components such as LNA) are included, or LC filters, antenna switch modules, couplers, diplexers, semiconductor integrated circuits, and the like are also included. Moreover, it is also possible to mount a plurality of electronic components of the same type or different types together in the same cavity of the wiring board.
[0026]
【The invention's effect】
According to the above-described wiring board of the present invention (claims 1 and 2), in the uppermost insulating layer in which the cavity is provided, at the corner where the via conductor penetrates, the width of the insulating layer in such a corner is The width is larger than the width of the insulating layer at the corner where the via conductor does not penetrate. Therefore, it is possible to provide a wiring board in which via conductors are easily arranged in such a wide corner.
[Brief description of the drawings]
FIG. 1A is a plan view schematically showing a first wiring board according to the present invention, and FIGS. 1B and 1C are views taken along line BB or CC in FIG. 1A. FIG.
FIG. 2 is an exploded perspective view of the wiring board of FIG. 1;
3 (A) to 3 (E) are schematic diagrams showing the steps of manufacturing the wiring board of FIG. 1;
4A is a perspective view showing a manufacturing process subsequent to FIG. 3E or the obtained wiring board of FIG. 1; FIGS. 4B and 4C are BB lines or C in FIG. 3A; Sectional drawing of the arrow taken along the -C line.
FIGS. 5A and 5B are plan views or perspective views showing a second wiring board according to the present invention.
FIGS. 6A and 6B are plan views or perspective views showing application forms of the wiring boards of FIGS. 1 and 5;
7A and 7B are plan views or perspective views schematically showing a conventional wiring board.
[Explanation of symbols]
1, 1a, 1b ... wiring boards 2 to 5 ... insulating layers 2a to 5a ... surface 6 ... ... Cavities 7a and 7b ares 10, 11 are concave portions 20 to 28, 31 to 38, 40 wiring layer V ………………… Via conductors R, r, D, d …………………… Radius (diameter)

Claims (2)

A plurality of insulating layers having a substantially rectangular shape in plan view;
A wiring layer formed on at least one of the surface and the interlayer of the plurality of insulating layers,
A cavity formed inside at least the uppermost insulating layer in plan view,
In the uppermost insulating layer, the diameter of the radius of the inner corner of the cavity adjacent to the corner through which the via conductor penetrates is equal to the radius of the radius of the inner corner of the cavity adjacent to the corner through which the via conductor does not penetrate. Larger than the diameter,
A wiring board characterized by the above-mentioned. A plurality of insulating layers having a substantially rectangular shape in plan view;
A wiring layer formed on at least one of the surface and the interlayer of the plurality of insulating layers,
A cavity formed inside at least the uppermost insulating layer in plan view,
In the uppermost insulating layer, the diameter of the concave portion having an arc-shaped cross section provided at the corner of the corner through which the via conductor penetrates has an arc-shaped cross-section provided at the corner of the corner not penetrated by the via conductor. Smaller than the diameter of the concave part,
A wiring board characterized by the above-mentioned.

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