JP2017098526A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board in which the size and the total number of elements to be mounted later are less likely to be restricted by the surface of a metallic heatsink inserted into a through hole penetrating between the front surface and the rear surface of a substrate body made from ceramic, and cracks and the like are less likely to occur in the vicinity of the joining part of the ceramic of the substrate body when the heatsink is brazed.SOLUTION: A wiring board 1 includes: a substrate body 2 made from ceramic c1-c4, having a front surface 3 and a rear surface 4, and having a through hole 6 penetrating between the front surface 3 and the rear surface 4; and a heatsink 11 inserted into the through hole 6. A step portion 7 protruding in a direction perpendicular to an axial direction of the through hole 6, is formed over an entire periphery on inner wall surfaces 8, 9 of the through hole 6 of the substrate body 2. A flange 12 opposed to the step portion 7 is provided so as to protrude, over an entire periphery on a side surface of the heatsink 11. A stress relaxing ring 16 is arranged over an entire periphery between the step portion 7 and a joining surface 15 opposed to the step portion 7. A brazing material 27 is provided between the ring 16, and the joining surface 15 and the step portion 7.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wiring board in which a heat sink made of metal for mounting an element having a relatively large amount of heat generation on the surface thereof is inserted into a through hole penetrating between the front and back surfaces of a substrate body made of ceramic.

  For example, between a ceramic package and a heat sink, a stress relaxation material made of a Cu-based metal and having a coating made of one or more alloys of Pt, Pd, Rh, Ni, and Co on the outer periphery is interposed. There has been proposed a ceramic package with a heat sink formed by joining the ceramic package and the heat sink with silver brazing or the like through such a stress relieving material (see, for example, Patent Document 1).

However, as shown in FIG. 1 of Patent Document 1, a ceramic package is formed by laminating a plurality of ceramic layers having a through hole on the center side in a plan view, and an opening width of the through hole. When the heat sink is brazed to the bottom surface side of the lowermost ceramic layer having the narrowest through the stress relaxation material, the mounting area of the surface of the heat sink does not have to be narrowed by the opening width of the through hole in the lowermost ceramic layer. I do not get. As a result, there is a problem that the size of an element such as an electronic component to be mounted later is restricted or the total number of elements to be mounted is limited.
Further, since the shrinkage stress generated in the heat sink due to the heat shrinkage after the brazing is transmitted to the adjacent ceramic layer through the entire thickness at the outer peripheral side of the heat sink, the brazing is performed. There was also a problem that cracks and peeling easily occur in the vicinity of the joint portion of the ceramic layer.

Japanese Examined Patent Publication No. 7-77788 (pages 1 to 3, Fig. 1)

  The present invention solves the problems described in the background art, and the surface of a metal heat sink inserted into a through-hole penetrating between the front surface and the back surface of a substrate body made of ceramic is used for an element to be mounted later. It is an object of the present invention to provide a wiring board that is less likely to be limited in size and total number and that is less likely to cause cracks or the like near the ceramic joint of the substrate body when the heat sink is brazed.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention provides a step provided on the inner wall surface of the substrate body that forms a through-hole penetrating between the front and back surfaces of the substrate body made of ceramic, and is inserted into the through-hole. It is conceived that the flange projecting outward from the entire circumference of the side surface of the heat sink to be opposed to each other and brazed between the two.
That is, the wiring board of the present invention (Claim 1) is made of ceramic, has a front surface and a back surface, and has a substrate body having a through-hole penetrating between the front surface and the back surface, and the penetration of the substrate body. A wiring board provided with a heat sink inserted into the hole, on the entire circumference of the inner wall surface forming the through hole of the substrate body, a stepped portion protruding in a direction perpendicular to the axial direction of the through hole, Alternatively, a stepped portion that is inclined so that the center side is closer to the back surface than the peripheral side in plan view is formed, and a flange facing the stepped portion is provided on the entire circumference of the side surface of the heat sink, and A stress relaxation ring is arranged on the entire circumference between the step portion and the joint surface facing the step portion in the flange, and at least between the stress relaxation ring and the joint surface of the flange, and the stress relaxation ring. And the above step The brazing material between is disposed, the brazing material along are disposed, it is characterized.

According to this, by brazing between the stepped portion of the substrate body forming the through hole and the flange projecting from the entire circumference of the side surface of the heat sink so as to face the stepped portion, Since the heat sink is joined, the following effects (1) to (3) can be achieved.
(1) The surface of the heat sink can be used as a mounting area for elements to be mounted later. That is, depending on the size of the through hole provided in the substrate body, the mounting area of the element to be mounted later is not easily limited. Therefore, the size of the element can be selected relatively freely, or the restriction on the total number of the elements can be reduced.
(2) The shrinkage stress generated in the heat sink as the heat shrinks after brazing forms the adjacent stepped portion only through a relatively thin flange projecting from the entire circumference of the side surface of the heat sink. Since it is transmitted to the ceramic of the substrate main body, cracks and peeling are less likely to occur in the vicinity of the joint portion of the brazed ceramic.
(3) A part of the shrinkage stress generated in the heat sink with the thermal shrinkage after the brazing is absorbed by the stress relaxation ring, so that cracks and peeling further occur in the vicinity of the joint. Therefore, the effect (2) can be achieved more remarkably.

The ceramic is a high-temperature fired ceramic such as alumina, mullite, or aluminum nitride, or a low-temperature fired ceramic such as glass-ceramic.
Further, the substrate main body may be in a form composed of a single ceramic layer or a form in which a plurality of ceramic layers are laminated. When the single-layer ceramic layer is used, a pad is formed on the front surface, a connection terminal is formed on the back surface, and a via conductor is formed along the thickness direction of the substrate body. ing. On the other hand, in the case where the plurality of ceramic layers are laminated, a wiring layer is formed between the ceramic layers in addition to the pads, connection terminals, and via conductors.
Furthermore, the heat sink is made of, for example, a W—Cu alloy or a Mo—Cu alloy.

Moreover, the back surface of the heat sink may be located outside the back surface of the substrate body. That is, the back surface of the heat sink may protrude from the substrate body. By adopting such a structure, it becomes easy to bring the back surface of the heat sink into contact with another member (for example, a mother board), so that it is easy to ensure heat dissipation. On the back surface of the heat sink, a plurality of female screw holes used for fixing to a mother board such as a printed board on which the wiring board is mounted may be formed.
Furthermore, the “facing” means that the joint surface of the flange is substantially parallel to the stepped portion.
The “step portion protruding in the direction orthogonal to the axial direction of the through-hole” includes a shape of a step portion perpendicular to the axial direction and an outer side in a side view (cross section) with respect to the axial direction. An inclined form is also included so that the center side is closer to the back surface of the substrate body than the side.
Furthermore, the brazing material is made of, for example, silver brazing (Ag—Cu-based alloy), and for example, a preform material previously formed into a rectangular frame shape or an annular shape in plan view is used.
The stress relaxation ring is made of pure copper, copper alloy, or the like. For example, by performing etching or the like on these flat plates, the plan view previously exhibits a ring shape (rectangular frame shape, pentagonal or more regular polygon). Frame shape, ring shape, etc.).
In addition, on the surface of the heat sink, an element having a relatively large calorific value such as a semiconductor element, a photoelectric conversion element, or an LED element is mounted.

In other words, the present invention may include a wiring board in which the surface of the heat sink opposite to the joint surface on which the brazing material of the flange is disposed is flush with the surface of the heat sink.
In this case, since the element can be mounted on the entire surface of the heat sink including the surface opposite to the joint surface on which the brazing material of the flange is disposed, the effect (1) is more remarkably achieved. It becomes possible to play.

Further, according to the present invention, the stress relaxation ring includes the entire overlapping portion of the joint surface of the flange of the heat sink and the stepped portion of the substrate body in a plan view, the outer peripheral side of the overlapping portion, or the overlapping. A wiring board (Claim 2) disposed on any of the inner peripheral sides of the part is also included.
Among the above, according to the embodiment in which the stress relaxation ring is disposed over the entire overlapping portion in plan view, the substrate body and the heat sink can be firmly bonded while exhibiting the effects (1) to (3). it can.
Moreover, according to the form which arrange | positions a stress relaxation ring in the outer peripheral side of the said duplication part, the said stress relaxation ring in the said through-hole should be arrange | positioned at the time of manufacture, producing said effect (1)-(3). The position can be set more accurately (effect (4)).
Furthermore, according to the embodiment in which the stress relaxation ring is arranged on the inner peripheral side of the overlapping portion, the gold coated on the surface of the brazing material to be described later at the time of production while exhibiting the effects (1) to (3). Inspection of the film and the like can be easily performed by visual inspection from the back side of the substrate body and the heat sink (effect (5)).
In addition, according to the embodiment in which the stress relaxation ring is arranged on the inner peripheral side of the overlapping portion, a space surrounded by the brazing material and the stepped portion on the inner peripheral side of the stress relaxation ring is unlikely to occur. When forming by electrolytic plating, the plating liquid does not accumulate, and it becomes easy to form a healthy gold film or the like (effect (6)).

Further, in the present invention, the brazing material is disposed between the inner peripheral side of the stress relaxation ring and the inner peripheral side of the joint surface of the flange in the heat sink in a plan view. In addition, the surface exposed to the outside of the heat sink includes at least a wiring board (Claim 3) covered with a gold film.
According to this, inadvertent corrosion of the surface exposed to the outside in the brazing material or the heat sink can be prevented in advance (effect (7)).
Incidentally, a nickel film is coated in advance as a base for the gold film.
Further, by forming a nickel film in advance on the entire surface of the stress relaxation ring, contact with the silver brazing constituting the brazing material is cut off, and silver inadvertently generated when the silver brazing is heated Prevents melt diffusion.

Further, according to the present invention, the through hole of the substrate body has a rectangular shape in plan view, and the long side and the short side of the through hole are formed with the step portions having different widths. In addition, the wiring board (Claim 4) is also included, in which the widths of the long side and the short side of the stress relief ring that is rectangular in plan view arranged in the step portion are different in the same relationship as the step portion. It is.
According to this, for example, when the plan view is a rectangular frame-shaped step portion, the width of the pair of short sides facing each other at the step portion is large and the width of the pair of long sides facing the step portion is small, The stress relaxation ring having a rectangular frame shape in plan view according to the size of the width is constituted by a pair of short sides having a large width and a pair of long sides having a small width. As a result, even if the wiring board includes a through hole having two types of step portions having different widths, the effect (2) can be reliably achieved.

Furthermore, in the present invention, in the vertical cross section perpendicular to the plane direction along the surface of the substrate body, the length of the stress relaxation ring in the plane direction is longer than the length of the stress relaxation ring in the vertical direction. A short wiring board (Claim 5) is also included.
According to this, in the cross section in the vertical direction between the step portion and the joint surface, the stress relaxation ring having a vertically long cross section is disposed via the brazing material, so that the space between the substrate body and the heat sink is The stress due to the difference in thermal expansion is absorbed by the deformation of the stress relaxation ring itself, so that cracks and peeling can hardly occur near the joint portion of the brazed ceramic (effect (8)).
According to the present invention, there is also provided a wiring board (Claim 6) in which a plurality of convex portions projecting toward an inner wall surface forming a through hole of the substrate body are formed on an outer periphery of the stress relaxation ring. included.
According to this, in the cross section in the planar direction along the surface of the substrate main body, the gap located between the outer periphery of the stress relaxation ring and the inner wall surface of the substrate main body forming the through hole is narrowed by a grade. Therefore, the effect (4) can be remarkably exhibited. In addition, in the stress relaxation ring, the portion excluding the portion where the convex portion is formed has a cross section in the vertical direction perpendicular to the planar direction along the surface of the substrate body, and the stress relaxation ring is in the plane direction. The length can be shorter than the vertical length of the stress relief ring. Therefore, the effect (8) can also be achieved.
In addition, the present invention includes a wiring board (Claim 7) in which the back surface of the heat sink projects outward from the back surface of the substrate body.
According to this, since the back surface of the heat sink can be easily brought into contact with another member (for example, a mother board) in the heat sink, the heat transmitted from the front surface side to the back surface side of the substrate body is transferred to the substrate. It can be easily dissipated from the back side of the main body to the outside (effect (9)).

(A) is a perspective view visually from the back side of the heat sink used in the wiring board of the present invention, (B) is an exploded perspective view visually from the surface side of the heat sink, the stress relaxation ring, and the substrate body, (C). FIG. 2 is a perspective view showing a wiring board of the present invention. FIG. 2 is a vertical sectional view taken along the line XX in FIG. The partial vertical sectional view which shows the junction part by brazing in the said wiring board. The partial vertical sectional view which shows the junction part by brazing of a different form. Furthermore, the partial vertical sectional view which shows the junction part by brazing of a different form. The partial vertical sectional view which shows the said junction part using the stress relaxation ring of a different form. (A) is a perspective view which shows the stress relaxation ring of FIG. 6, (B) is a perspective view which shows the stress relaxation ring of a further different form. 8 is a horizontal sectional view showing a wiring board using the stress relaxation ring of FIGS. 6 and 7A. FIG. The perspective view which shows the wiring board of a different form. The partial vertical sectional view which shows the junction part vicinity of another form. The partial vertical sectional view which shows the junction part vicinity which is an application form of the said junction part.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1A is a visual perspective view from the back surface 14 side of the heat sink 11 used in the wiring board 1 of the present invention, and FIG. 1B is the heat sink 11, the stress relaxation ring 16, and the substrate body 2, respectively. It is a disassembled perspective view by the vision from the surface 3, 13 side in FIG.
As shown in FIGS. 1A and 1B, the heat sink 11 has a front surface 13 and a rear surface 14 that are rectangular (rectangular) in plan view, and a plan view that protrudes horizontally from the four sides of the front surface 13 in a horizontal direction. And a rectangular frame-shaped flange 12. The surface 13a of the flange 12 is flush with the surface 13 and the side opposite to the surface 13a (back surface 14) is a joint surface 15 used for brazing described later. The heat sink 11 is made of, for example, a W-10 wt% Cu alloy or a Mo-30 wt% Cu alloy.

  As shown in the lower part of FIG. 1B, the substrate body 2 has a front surface 3 and a back surface 4 having a rectangular outer shape in plan view, and a rectangular shape in plan view in which the heat sink 11 is inserted therebetween. And a through hole 6. The through hole 6 is a direction perpendicular to the axial direction of the through hole 6 between the inner wall surface 8 on the front surface 3 side and the inner wall surface 9 on the back surface 4 side of the substrate body 2. A step 7 having a rectangular frame shape in plan view is formed. Between the surface 3 and the inner wall surface 8, there is formed a shallow step portion 3a that is included in a part of the surface 3 and has a rectangular frame shape in plan view, and in the vicinity of the center of every four sides in the step portion 3a. A plurality of pads 10 are formed. The substrate body 2 is made of a ceramic in which a plurality of ceramic layers are integrally laminated as will be described later.

  Further, as shown in the middle of FIG. 1B, the planar view is a rectangular frame shape between the joint surface 15 of the flange 12 of the heat sink 11 and the stepped portion 7 of the through hole 6 of the substrate body 2. A stress relief ring 16 is disposed. The stress relaxation ring 16 is made of, for example, pure copper (electrocopper) or a copper alloy, and has a pair of long sides 17 and a pair of short sides 18 that are opposed to each other in a plan view, and a rectangular plan view surrounded by these. And a space 19. The cross sections of the long side 17 and the short side 18 are both rectangular or square. The space 19 is slightly larger than the main body portion excluding the flange 12 of the heat sink 11 in plan view. A nickel coating (26) described later is formed (coated) on the entire surface of the stress relaxation ring 16 in advance.

The wiring board 1 is assembled as follows.
A sheet-shaped brazing material (27), which will be described later, which is preformed in the shape of a rectangular frame in plan view, is attached to the top and bottom surfaces of the stress relaxation ring 16, and is outlined in FIG. 1 (B). As indicated by the arrows, after placing on the stepped portion 7 of the substrate body 2 forming the through hole 6, the heat sink 11 is further inserted into the through hole 6 from the surface 3 side of the substrate body 2. Insert with the back side 14 facing downward. At this time, the lower layer brazing material (27), the stress relaxation ring 16, the upper layer brazing material (27), and the flange 12 of the heat sink 11 are sequentially stacked on the step portion 7 of the through hole 6. In this state, the substrate body 2 having the heat sink 11, the stress relaxation ring 16, and the brazing material (27) is heated to melt the brazing material (27). Further, the heat sink 11 and the substrate body 2 brazed with the stress relaxation ring 16 interposed therebetween are sequentially immersed in a nickel plating bath and a gold plating bath, and the pad 10, the heat sink 11, and the brazing material exposed to the outside are exposed. Electrolytic nickel plating and electrolytic gold plating are sequentially applied to the surface of the conductor such as (27).

As a result, as shown in FIG. 1C, the vertical cross-sectional view of FIG. 2, and the enlarged vertical cross-sectional view of FIG. 3, the substrate body 2 that forms the through-hole 6 is formed in the through-hole 6 of the substrate body 2. The back surface 14 of the heat sink 11 passes through the inner wall surfaces 8 and 9 and slightly protrudes outward (lower side in the drawing) from the back surface 4 of the substrate body 2, and on the stepped portion 7 of the through hole 6. Thus, the wiring substrate 1 is obtained in which the joining surface 15 of the flange 12 of the heat sink 11 is joined via the brazing material 27 having a substantially parallelogram-shaped vertical section and the stress relaxation ring 16 surrounded by the brazing material 27.
As shown in FIGS. 2 and 3, the substrate body 2 is formed by integrally laminating ceramic layers c1 to c4 mainly composed of alumina, for example, and the pad 10 is interposed between the ceramic layers c1 to c4. Wiring layers 21 and 22 are individually formed, and a plurality of connection terminals 20 are formed on the back surface 4 of the substrate body 2. The wiring portion of the pad 10, the wiring layers 21 and 22, and the connection terminal 20 are electrically connected via via conductors 23 that individually penetrate the ceramic layers c <b> 1 to c <b> 4.
The pad 10, the connection terminal 20, the wiring layers 21, 22 and the via conductor 23 are mainly made of tungsten (W) or molybdenum (Mo). The substrate body 2 is manufactured in advance by a known method (green sheet punching process, conductive paste filling / printing process, laminating / firing process of a plurality of green sheets).

As shown in FIG. 2, the back surface 14 of the heat sink 11 is formed with a plurality of female screw holes 25 for screwing and fixing the wiring board 1 to a mother board such as a printed board (not shown). Further, a flat photoelectric conversion element 24 is mounted on the surface 13 of the heat sink 11, and the element 24 and the pad 10 are electrically connected via a bonding wire w. A lid plate (not shown) for sealing the element 24 from the outside is attached above the element 24.
Further, as shown in FIG. 3, since the entire surface of the stress relaxation ring 16 is coated with a nickel film 26, the copper component of the ring 16 contacts the silver component of the brazing material 27 and corrodes. Has been prevented. Further, a gold film 29 is formed on the surface exposed to the outside in the brazing material 27 with a required thickness through a nickel film 28. The nickel coating 28 and the gold coating 29 are similarly formed on the surfaces of the pad 10, the heat sink 11, and the connection terminal 20 exposed to the outside.

Further, as shown in FIG. 3, the stress relaxation ring 16 is substantially entirely in an overlapping portion between the joint surface 15 of the flange 12 of the heat sink 11 and the stepped portion 7 forming the through hole 6 of the substrate body 2 in plan view. Is arranged.
In addition, as shown in the enlarged vertical sectional view of FIG. 4 without being limited to the above-described form, the rectangular stress relaxation ring 16 having a small vertical section width and a bonding surface 15 of the flange 12 of the heat sink 11 in plan view, It is good also as a form arrange | positioned in the outer peripheral side of the overlap part with the step part 7 of the through-hole 6 of the board | substrate body 2. As shown in FIG.
Further, as shown in the enlarged vertical sectional view of FIG. 5, the (length) width w along the plane direction parallel to the surface 3 of the substrate body 2 is higher than the height (length) h orthogonal to the plane direction. The larger stress relaxation ring 16 may be arranged on the inner peripheral side of the overlapping portion of the joint surface 15 of the flange 12 of the heat sink 11 and the stepped portion 7 forming the through hole 6 of the substrate body 2 in plan view. . According to such a form, the stress relaxation ring 16 can be freely disposed at an arbitrary position between the stepped portion 7 and the joint surface 15.

  Furthermore, as shown in the partially enlarged cross-sectional view of FIG. 6, the plan view has a square shape between the step portion 7 that forms the through hole 6 of the substrate body 2 and the joint surface 15 of the flange 12 in the heat sink 11. The stress relaxation ring 16 provided with a pair (plurality) of outwardly protruding portions 16u for each outer periphery of the four sides 7 may be disposed, and the brazing material 27 may be disposed so as to surround the stress relaxation ring 16 as a whole. As shown in FIG. 7A, the stress relaxation ring 16 is formed by projecting a pair of protrusions 16u along the vertical direction for each outer periphery of the four sides 17, and etching the material such as electrolytic copper. It can be obtained by processing or punching. As shown in FIG. 7B, a pair of conical convex portions 16v may be provided so as to protrude from the outer periphery of the four sides 17 one by one. The stress relaxation ring 16 having the convex portion 16v is manufactured by, for example, precision casting the material.

As shown in the horizontal sectional view of FIG. 8, when the stress relaxation ring 16 of FIGS. 6 and 7A is inserted into the through hole 6 of the substrate body 2 having the front surface 3 and the rear surface 4 that are square in plan view. The tip portions of the pair of convex portions 16 u that protrude from the outer periphery of each side 17 of the stress relaxation ring 16 approach the inner wall surface 8 of the substrate holder 2 that forms the through hole 6. As a result, the stress relaxation ring 16 can be accurately arranged on the inner wall surface 8 side between the stepped portion 7 and the joint surface.
The convex portion 16u of the stress relaxation ring 16 may protrude only on the upper surface side or the lower surface side of each side 17.

According to the wiring board 1 including the above embodiments, at least the effects (1) to (3) and (7) can be achieved. Moreover, in the form shown in FIG. 4, the said effect (4) can be show | played further. Moreover, as shown in FIGS. 3 to 6, the effect (9) can be achieved by causing the back surface 14 of the heat sink 11 to protrude outward from the back surface 4 of the substrate body 2.
Furthermore, in the embodiment shown in FIG. 5, the effects (5) and (8) can be further achieved. In addition, in this embodiment, there is no space surrounded by the brazing material 27, the heat sink 11, and the stepped portion 7 on the inner peripheral side of the stress relaxation ring 16, and when the gold film 29 is formed by electrolytic plating, A sound gold film 29 can be reliably formed by preventing generation of a liquid pool (the effect (6)).
In addition, the effects (1) to (9) can be achieved by the modes shown in FIGS.

Note that the front surfaces 3 and 13 and the rear surfaces 4 and 14 of the substrate main body 2 and the heat sink 11 may have a square shape in plan view as shown in FIGS.
Further, instead of the flat plate-like connection terminal 20 provided on the back surface 4 of the substrate body 2, a connection terminal formed of a long and thin bar-shaped conductor pin may be used.
Further, the width of the long side and the short side of the stepped portion 7 of the substrate body 2 in plan view may be different. In the case of this form, the widths of the long side 17 and the short side 18 in the stress relaxation ring 16 are also different corresponding to the widths of the opposing stepped portions 7.

FIG. 9 is a perspective view showing a wiring board 30 having a form different from that of the wiring board 1.
As shown in FIG. 9, the wiring board 30 has a through hole 36 that is circular in plan view passing between the front surface 3 and the back surface 4 of the substrate body 2 similar to the above, and is formed on the inner wall surface of the through hole 36. Is formed with a step portion (not shown) having an annular shape in plan view. A shallow step portion 33 having an annular shape in plan view is located between the surface 3 of the substrate body 2 and the inner wall surface of the through hole 36. A pad 10 is formed.
A heat sink 31 having a circular plan view is inserted into the through hole 36 in the same manner as described above. Between the flange 32 and the step portion in the through hole 36, each of the heat sinks 31 shown in FIGS. By arranging the brazing material 27 via the stress relaxation ring 16 having the form, the substrate body 2 and the heat sink 31 are joined.
Also with the wiring board 30 as described above, the effects (1) to (9) similar to the bonding forms of the wiring board 1 can be obtained according to the individual forms.
The through hole 36, the heat sink 31 and the like may have an elliptical shape or an elliptical shape in plan view.

FIG. 10 is a partially enlarged cross-sectional view similar to the above, showing the vicinity of the joint using the substrate main body 2a, the heat sink 11a, and the stress relaxation ring 16a of the wiring boards 1 and 30 different from the above.
As shown in FIG. 10, the substrate body 2a has a through hole 6a penetrating between the same front surface 3 and back surface 4, and a flat surface between the inner peripheral surfaces 8 and 9 of the through hole 6a. A stepped portion 7 a is formed so that the center side is closer to the back surface 4 than the outer peripheral side as viewed. The stepped portion 7a is along a direction slightly inclined from the direction perpendicular to the axial direction of the through hole 6a and protrudes toward the center side of the substrate body 2a.
In order to form the stepped portion 7a, for example, a green sheet to be the ceramic layer c2 is punched to form a through hole having a rectangular or circular shape in plan view, and then the front end surface with respect to the periphery of the through hole. A method in which a four-sided pyramid-shaped punch or a conical punch whose tip end surface is inclined is pressed and plastically deformed is used.

Further, as shown in FIG. 10, the heat sink 11 a has the same front surface 13 and rear surface 14, and on the outer peripheral side of the front surface 13, the front surface 13 a flush with the front surface 13 and the substrate body 2. A flange 12a having a joint surface 15a that faces the step 7a and is inclined so as to be parallel to the step 7a extends outward.
Further, as shown in FIG. 10, the upper piece and the lower piece are substantially parallel in a vertical section on the outer peripheral side of the overlapping portion between the step portion 7a of the substrate body 2a and the joint surface 15a of the flange 12a in plan view. A brazing material 27 similar to that described above is disposed so as to surround the stress relaxation ring 16a which has a parallelogram shape as a whole. A nickel coating 28 and a gold coating 29 similar to those described above are formed on the inner and outer exposed surfaces of the brazing material 27.

According to the wiring boards 1 and 30 having the joint portion using the substrate body 2a, the heat sink 11a, and the stress relaxation ring 16a as described above, the stress generated when the heat sink 11a is thermally contracted after brazing. Since the occurrence of cracks and peeling near the outer peripheral end (base end portion) of the stepped portion 7a of the substrate body 2a can be further suppressed, the effect (2) can be further exhibited.
Note that the stress relaxation ring 16a may be arranged on substantially the entire overlapping portion of the stepped portion 7a of the substrate body 2 and the joint surface 15a of the flange 12a in the plan view or on the inner peripheral side of the overlapping portion. good.
Moreover, it is good also as a form which protruded the said some convex parts 16u and 16v on the outer periphery of the said stress relaxation ring 16a.
Furthermore, the joint surface 15a is not limited to a single inclined surface, and may be a form in which a plurality of inclined surfaces are adjacent to each other, or a form in which the convex surface is a gently curved surface with a convex upward in a vertical section.

FIG. 11 is a similar partially enlarged vertical sectional view showing the vicinity of the joint portion using the substrate main body 2b and the heat sink 11b in a form different from the above in the wiring boards 1 and 30. FIG.
As shown in FIG. 11, the substrate body 2b has a through hole 6b penetrating between the same front surface 3 and back surface 4, and the through hole 6b has a width (inner diameter) along the axial direction thereof. Have three inner wall surfaces 8, 9b, 9 different from each other, and two step portions 7, 7b inside and outside (upper and lower) between them. In order to form the stepped portions 7 and 7b, the substrate body 2b is formed by laminating five ceramic layers c1 to c5 having different widths or inner diameters of through holes punched when green sheets are formed. Yes.

Further, as shown in FIG. 11, the heat sink 11b has a surface 13 and a back surface 14 similar to the above. On the outer peripheral side of the surface 13, the surface 13a flush with the surface 13 and the substrate body 2 are provided. A flange 12b having a pair of upper and lower joining surfaces 15 and 15b that individually face the step portions 7 and 7b and are parallel to the step portions 7 and 7b extends outward.
Furthermore, as shown in FIG. 9, between the stepped portions 7 and 7b of the substrate main body 2b and the joint surfaces 15 and 15b of the heat sink 11b, two stresses having a slightly smaller cross-sectional area than the above and a rectangular shape. A brazing material 27 similar to the above is disposed in a deformed cross section (square glasses shape or stepped double rectangular shape) so as to individually surround the relaxation ring 16. A nickel coating 28 and a gold coating 29 similar to those described above are formed on the inner and outer exposed surfaces of the brazing material 27.

According to the wiring boards 1 and 30 having the joint portion using the substrate body 2b, the heat sink 11b, and the two stress relaxation rings 16 as described above, the stress generated when the heat sink 11b is thermally contracted after brazing. On the other hand, the stress can be further reduced by the two stress relaxation rings 16. As a result, it is possible to further suppress the occurrence of cracks and delamination in the ceramics in the vicinity of the stepped portions 7 and 7b and the inner wall surface 9b of the substrate body 2b bonded to the brazing material 27, so that the effect (2) is further exhibited. It becomes possible.
The stepped portions 7 and 7b of the through hole 6b and the joint surfaces 15 and 15b of the flange 12b of the heat sink 11b may be inclined surfaces of the form shown in FIG.
Further, the stepped portion 7n of the through hole 6b and the joint surface 15n of the flange 12b of the heat sink 11b may be the same number and three or more.
Further, the two stress relaxation rings 16 may be integrated as a single step, or a plurality of the convex portions 16u and 16v may be provided on each outer periphery.

The present invention is not limited to the embodiments described above.
For example, the ceramic constituting the substrate bodies 2, 2a, 2b may be a high-temperature fired ceramic such as mullite or aluminum nitride, or a low-temperature fired ceramic such as glass-ceramic. In the latter case, silver or copper is applied to conductors such as the pads 10, connection terminals 20, wiring layers 21 and 22, and via conductors 23.
Further, the through hole penetrating between the front surface 3 and the back surface 4 of the substrate body 2 or the like may be a regular polygon or a deformed polygon that is a pentagon or more in a plan view. The step portions formed on the inner wall surfaces of these through holes are in the form of a regular polygon frame shape or a deformed polygon frame shape of a pentagon or more in plan view.

Furthermore, the surface 3 of the substrate body 2 or the like is positioned higher in the thickness direction than the opening of the through hole 6 or the like, and above the surface 13 of the heat sink 11 or the like inserted into the through hole 6 or the like, It is good also as a form which has the cavity opened on the surface 3. FIG.
The pad 10 may be formed directly on the surface 3 of the substrate body 2 or the like.
In addition, the substrate body 2 or the like has a plurality of through holes 6 or the like penetrating between the front surface 3 and the back surface 4, and the heat sink 11 or the like is inserted into each of the through holes 6 or the like. A configuration may be employed in which the heat sink 11 or the like is brazed directly through the relaxation ring 16 or the like or only by the brazing material 27.

  According to the present invention, the surface of the metal heat sink inserted into the through-hole penetrating between the front surface and the back surface of the substrate body made of ceramic is less likely to limit the size and total number of elements to be mounted later. In addition, when the heat sink is brazed, it is possible to reliably provide a wiring board in which cracks and peeling do not easily occur in the ceramic portion of the substrate body.

1, 30 ………………………… Wiring board 2, 2a, 2b ………………… Board body 3 …………………………………… Surface 4 …………… …………………… Back 6, 6 a, 6 b, 36 ………… Through hole 7, 7 a, 7 b …………………… Step 8, 9, 9 b ……………… Inside Wall surface 11, 11a, 11b, 31 ... Heat sink 12, 12a, 12b, 32 ... Flange 15, 15a, 15b ………… Joint surface 16, 16a ……………… Stress relaxation ring 16u, 16v ……… …………… Protrusions 27 ……………………………… Brazing materials c1 to c5 ……………………… Ceramic layer (ceramic)
h ………………………………… Section relief height (length)
w ………………………………… Stress relief ring cross-section width (length)

Claims (7)

A wiring board comprising a substrate body made of ceramic, having a front surface and a back surface, and having a through hole penetrating between the front surface and the back surface, and a heat sink inserted into the through hole of the substrate body. There,
The entire circumference of the inner wall surface forming the through hole of the substrate body is inclined such that a stepped portion projecting in a direction perpendicular to the axial direction of the through hole, or the central side is closer to the back side than the peripheral side in plan view. A stepped portion is formed, and a flange facing the stepped portion is provided on the entire circumference of the side surface of the heat sink,
A stress relaxation ring is disposed on the entire circumference between the step portion and the joint surface facing the step portion in the flange, and at least between the stress relaxation ring and the joint surface of the flange and the stress relaxation. The brazing material is disposed between the ring and the stepped portion,
A wiring board characterized by that. The stress relieving ring may be either the entire overlapping portion of the joint surface of the flange of the heat sink and the stepped portion of the substrate body in a plan view, the outer peripheral side of the overlapping portion, or the inner peripheral side of the overlapping portion. Arranged in the
The wiring board according to claim 1. In plan view, the brazing material is disposed between the inner peripheral side of the stress relaxation ring and the inner peripheral side of the joint surface of the flange in the heat sink, and the brazing material and the heat sink are exposed to the outside. The surface to be coated is at least a gold film,
The wiring board according to claim 1 or 2, wherein The through hole of the substrate body has a rectangular shape in plan view, and the long side and the short side of the through hole are formed with the stepped portions having different widths and are arranged in the stepped portion. The width of the long side and the short side of the rectangular stress relaxation ring in plan view is different in the same relationship as the stepped portion,
The wiring board according to any one of claims 1 to 3, wherein In the vertical cross section perpendicular to the plane direction along the surface of the substrate body, the length of the stress relaxation ring in the plane direction is shorter than the length of the stress relaxation ring in the vertical direction.
The wiring board according to any one of claims 1 to 4, wherein the wiring board is provided. On the outer periphery of the stress relaxation ring, a plurality of convex portions projecting toward the inner wall surface forming the through hole of the substrate body are formed.
The wiring board according to any one of claims 1 to 5, wherein The back surface of the heat sink protrudes outward from the back surface of the substrate body.
The wiring board according to any one of claims 1 to 6, wherein

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