JP4427154B2 - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a ceramic circuit board where an aluminum plate is bonded directly to a ceramic substrate that cracking takes place in the substrate due to thermal stress or residual stress when the substrate is subjected to cooling/heating cycle. SOLUTION: The ceramic circuit board comprises a ceramic substrate and a metal plate principally comprising aluminum bonded directly to the surface of the ceramic substrate wherein a thin part having thickness in the range of 1/6-5/6 of the thickness at the mounting face part of the metal plate is provided on the inside of the outer circumferential fringe of the metal plate within a range of 1.0 mm therefrom.

Description

表１から明らかなように、参考例２〜５のようにＳｉペレットとの接合面に溝を設けたものは、いずれも熱抵抗不良が抑制されていることがわかった。特に、溝の深さ、幅、長さ、間隔を、本発明における好ましい値としたものは、熱抵抗不良が大幅に抑制されていることがわかった。
【００８０】
これに対して、アルミニウム板のＳｉペレットとの接合面に溝を設けず、Ｓｉペレットとアルミニウム板とを接合した比較例２では、熱抵抗不良が発生していることがわかった。
【００８１】
以上の結果より、アルミニウム板のＳｉペレット接合面に複数の溝を設けることによって、ハンダ巣の生成又は成長を抑制し、熱抵抗不良を大幅に抑制することができることが確認された。
【００８２】
参考例６〜８
参考例１のアルミニウム板をＡｌ−１０ｗｔ％Ｓｉ板に変えたものを参考例６、参考例１の窒化アルミニウム基板を窒化ケイ素基板に変えたものを参考例７、参考例１のアルミニウム板をＡｌ−１０ｗｔ％Ｓｉ板に変えさらに窒化アルミニウム基板を窒化ケイ素基板に変えたものを参考例８とした。
【００８３】
このようなセラミックス回路基板に対し、アルミニウム板のピール強度並びに冷熱サイクル試験（ＴＣＴ）として、２３３Ｋ×３０分→ＲＴ×１０分→３９８Ｋ×３０分→ＲＴ×１０分を１サイクルとした通常より厳しい条件にて、１０００サイクルおよび２０００サイクル行った場合のセラミックス基板へのクラックの有無を確認した。
【００８４】
また、比較のため比較例１のセラミックス回路基板についても同様の測定を行った。その結果を表２に示す。
【００８５】
【表２】

表２に示されるように、アルミニウム板にＳｉを含有させた場合のほうがピール強度が向上していることがわかる。
【００８６】
また、ＴＣＴ試験結果を見ても、参考例のものは試験条件が２３３Ｋ×３０分→ＲＴ×１０分→３９８Ｋ×３０分→ＲＴ×１０分と通常よりも厳しい条件にもかかわらず、１０００サイクルまではセラミックス基板へのクラックの発生は確認されなかった。
【００８７】
それに対し、比較例のものは若干の剥がれが確認された。これはアルミニウム板の外周部に薄肉部がないため応力緩和がなされていないためであるといえる。なお、ＴＣＴ試験の「ややあり」との表記は若干の割れ現象が確認されたものを示すものである。
【００８８】
さらに、窒化アルミニウム基板と窒化ケイ素基板とを比較すると、窒化ケイ素基板（参考例７および８）を用いたものの方が優れたＴＣＴ試験特性を示すことが分かった。
【００８９】
【発明の効果】
本発明のセラミックス回路基板は、冷熱サイクルが付加された場合等に、主としてアルミニウムからなる金属板に生じる熱応力や残留応力を分散させることによって金属板の外周縁部への応力集中を抑制し、セラミックス回路基板にクラックが発生することを抑制することができる。
【００９０】
また、本発明の半導体装置は、セラミックス回路基板に半導体素子を接合する際に用いたハンダにハンダ巣が形成されるのを抑制し、熱抵抗不良や剥離等を抑制することができる。
【図面の簡単な説明】
【図１】 金属板の外周縁部内側に薄肉部を設けた場合の一例を示す外観図。
【図２】 金属板の外周縁部内側に薄肉部を設けた場合の一例を示す断面図。
【図３】 金属板の外周縁部内側に孔を設けた場合の一例を示す外観図。
【図４】 図３の一部分を拡大した平面図。
【図５】 孔の形状を矩形とした場合の一例を示す平面図。
【図６】 金属板の外周縁部内側に孔を設けた場合の一例を示す断面図。
【図７】 孔の深さ方向の形状の他の例を示す断面図。
【図８】 孔を貫通孔とした場合の一例を示す断面図。
【図９】 金属板の外周縁部内側に不連続な溝を設けた場合の一例を示す外観図。
【図１０】 図９の一部分を拡大した平面図。
【図１１】 溝の断面形状の一例を示す断面図。
【図１２】 溝の断面形状の他の例を示す断面図。
【図１３】 半導体装置の一例を示す外観図。
【図１４】 半導体装置の一例を示す断面図。
【図１５】 冷熱サイクル試験実施後の参考例１の応力分布を表す図。
【図１６】 冷熱サイクル試験実施後の実施例１の応力分布を表す図。
【図１７】 冷熱サイクル試験実施後の実施例２の応力分布を表す図。
【図１８】 参考例２〜５に用いたアルミニウム板の一例を示した概略図。
【符号の説明】
１……セラミックス回路基板
２……セラミックス基板
３……アルミニウム板
３ａ……外周縁部
３ｂ……薄肉部
５……孔
７……溝
９……ハンダ層
１０……半導体素子
１１……溝[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a ceramic circuit board useful as a semiconductor mounting board, and more particularly to a ceramic circuit board formed by directly bonding a metal plate mainly made of aluminum on a ceramic board..
[0002]
[Prior art]
Conventionally, a copper-clad ceramic circuit board in which a copper plate is bonded to the surface of a ceramic substrate has been used as a substrate used for mounting a high-power electronic component such as a power module.
[0003]
This ceramic circuit board is produced by directly bonding or brazing copper to a ceramic substrate such as alumina or aluminum nitride.
[0004]
As disclosed in JP-A-52-37914, the direct bonding substrate is made of an oxygen-free copper plate by using a copper plate containing oxygen or heating in an oxidizing atmosphere using an oxygen-free copper plate. After copper oxide is generated on the surface, the copper plate and the alumina substrate are stacked and heated in an inert atmosphere to form a composite oxide of copper and aluminum at the interface between the copper plate and the alumina substrate. Join.
[0005]
In the case of a copper / aluminum nitride direct bonding substrate, as disclosed in, for example, Japanese Patent Laid-Open No. 3-93687, an aluminum nitride substrate is treated in advance at a temperature of about 1000 ° C. to generate an oxide on the surface. Then, the copper plate and the aluminum nitride substrate are bonded via the oxide layer. The joining method using such an oxide layer deteriorates the thermal conductivity of the metal-bonded ceramic substrate because the oxide itself does not necessarily have a good thermal conductivity.
[0006]
Also, when copper is brazed to alumina or aluminum nitride, a low melting point brazing material or an alloy element for lowering the melting point or an alloy element for improving the wetting with ceramics is added between the copper plate and the ceramic circuit board. Join with the brazing filler metal. Although the copper / ceramic circuit board as described above is widely used, there are some problems in manufacturing and practical use. Among them, the most serious problem is a failure due to electrical continuity between the front and back of the substrate when a crack occurs in the ceramic substrate during mounting and use of the electronic component.
[0007]
The occurrence of such cracks is due to the fact that the thermal expansion coefficient of copper is about an order of magnitude greater than that of ceramics. That is, when these are joined, they are heated to close to 1000 ° C., and therefore, when they are cooled from the joining temperature to room temperature, a great thermal stress is generated inside the ceramic circuit board due to the difference in thermal expansion coefficient.
[0008]
Further, due to heat generation and cooling during use, the temperature of the ceramic circuit board changes, and a fluctuating thermal stress is generated, which may cause a crack in the ceramic substrate.
[0009]
At present, instead of copper as described above, aluminum having a thermal expansion coefficient relatively close to that of ceramics is used for bonding. In addition, since aluminum has a low melting point, it can be bonded at a lower temperature than copper, and cracking due to shrinkage during cooling can be reduced. Furthermore, as described above, since aluminum is a softer metal than copper, the aluminum plate itself can flexibly cope with the thermal expansion associated with heat generation and cooling during use, reducing the stress that causes cracks in the ceramic substrate. It is also possible.
[0010]
[Problems to be solved by the invention]
However, in recent years, with the development of power modules for electric vehicles, there has been a demand for the development of circuit boards that are further excellent in heat cycle resistance. For example, in the case of use conditions such as an electric vehicle where the temperature change is large and the vibration is large, the circuit board is required to have a heat cycle resistance of 500 times or more. In the copper / ceramic circuit board currently used, it is impossible to meet such a demand, and even in a normal aluminum / ceramic circuit board which is said to have relatively few cracks. It is difficult to withstand the cold cycle.
[0012]
The object of the present invention is to improve the thermal cycle resistance of ceramic circuit boards bonded with metal plates mainly made of aluminum, and to prevent the occurrence of cracks even in the use in harsh environments. It is an object of the present invention to provide a ceramic circuit board having the above.
[0016]
[Means for Solving the Problems]
  BookThe ceramic circuit board of the present invention is a ceramic circuit board comprising a ceramic substrate and a metal plate that is directly bonded to the surface of the ceramic substrate and is mainly made of aluminum, wherein the metal plate is opposite to the bonding surface with the ceramic substrate. It has a plurality of holes provided inside the outer peripheral edge of the side surface.
[0017]
The plurality of holes are preferably formed linearly at predetermined intervals along the outer peripheral edge of the metal plate. Further, the plurality of holes have a diameter of 0.3 mm or more and 1.0 mm or less, a distance between adjacent holes of 0.3 mm or more and 1.0 mm or less, and an edge of the hole is outside the metal plate. It is preferable to be provided in a part separated by 0.3 mm or more from the peripheral part.
[0018]
  The ceramic circuit board of the present invention is a ceramic circuit board comprising a ceramic board and a metal plate joined to the surface of the ceramic board and mainly made of aluminum, wherein the metal board is a joint surface with the ceramic board. Is provided on the inner side of the outer peripheral edge of the opposite surface, and has a plurality of discontinuous grooves along the outer peripheral edge.The discontinuous groove has a depth of 1/6 or more and 5/6 or less of a thickness of a portion to be a mounting surface of the metal plate, a width of 0.05 mm or more and 1.0 mm or less, and the groove Is provided at a portion separated by 0.3 mm or more from the outer peripheral edge of the metal plate.It is characterized by this.
[0020]
Furthermore, for example, an Al—Si alloy plate can be used as the metal plate mainly made of aluminum.
[0025]
In the ceramic circuit board of the present invention, by providing a plurality of holes inside the outer peripheral edge of a metal plate mainly made of aluminum, the stress generated due to the difference in the thermal expansion coefficient between the metal plate and the ceramic substrate is alleviated, and the cooling cycle It is possible to suppress the occurrence of cracks due to the above.
[0026]
In addition, a plurality of holes are formed linearly at predetermined intervals along the outer peripheral edge of the metal plate, the diameter is 0.3 mm or more and 1.0 mm or less, and the distance between adjacent holes is 0.3 mm or more. Generation of cracks can be further suppressed by providing the edge of the hole at a portion of 1.0 mm or less and 0.3 mm or more away from the outer peripheral edge of the metal plate.
[0027]
In the ceramic circuit board of the present invention, the metal plate and the ceramic substrate are formed by forming a plurality of discontinuous grooves along the outer peripheral edge inside the outer peripheral edge of the surface of the metal plate where the ceramic substrate is not bonded. It is possible to relieve the stress generated due to the difference in thermal expansion coefficient between the two, and to further suppress the generation of cracks due to the cooling / heating cycle or the like.
[0028]
The depth of the discontinuous groove is 1/6 or more and 5/6 or less of the thickness of the portion to be the mounting surface of the metal plate, the width is 0.05 mm or more and 1.0 mm or less, and the edge of the groove is Generation of cracks can be further suppressed by providing the metal plate in a portion separated by 0.3 mm or more from the outer peripheral edge of the metal plate.
[0031]
In the above-described ceramic circuit board of the present invention, it is necessary for the ceramic circuit board to use, as the ceramic board, a material mainly composed of at least one material selected from the group consisting of alumina, aluminum nitride and silicon nitride. It is possible to improve properties such as strength and thermal conductivity.
[0032]
Furthermore, by using a metal plate mainly made of aluminum as an Al—Si alloy plate, the bonding strength between the aluminum plate and various ceramics can be improved. Therefore, it is possible to further suppress the occurrence of cracks in the ceramic plate by applying it to the aluminum plate improved in shape as described above.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
  FIG.Reference exampleThis shows an example of the ceramic circuit board.
[0034]
  SEThe Ramics circuit board 1 is obtained by bonding an aluminum plate 3 to a ceramic substrate 2, for example. At this time, when the outer peripheral edge portion of the aluminum plate 3 is 3a, the inner side of the outer peripheral edge portion is the thin portion 3b. Here, the inner side of the outer peripheral edge is a portion of a constant distance from the outer peripheral edge toward the center.
[0035]
For example, when directly joining an aluminum plate to a ceramic plate, the aluminum plate is heated to the melting point or more of the aluminum plate, but by providing a thin portion inside the outer peripheral edge of the aluminum plate, the stress generated in the outer peripheral edge of the aluminum plate is reduced to aluminum. Absorption is caused by plastic deformation of the thin portion of the plate, and it is possible to suppress the occurrence of cracks in the ceramic plate. In addition, not only when joining the aluminum plate and ceramic plate, but also when using them after joining them, thermal stress is generated by the thermal cycle. It is possible to suppress the occurrence of cracks in the ceramic plate by absorbing the thin plate portion of the aluminum plate due to plastic deformation.
[0036]
As the shape of the thin portion 3b, for example, as shown in FIG. 2, the surface of the aluminum plate that is not bonded to the ceramic plate is shaved to provide a step. Examples of a method for forming such a thin portion 3b include a method of processing by etching or the like in addition to a method of mechanically processing. The thin portion 3b may be formed after joining the ceramic plate and the aluminum plate, but by forming it before joining the ceramic plate, it is possible to suppress the occurrence of cracks in the ceramic plate due to stress during joining. Therefore, it is more effective.
[0037]
For example, if the length from the outer peripheral edge of the aluminum plate is W and the thickness of the thin portion is T, W is 0.3 mm to 1.0 mm, and T is aluminum. It is preferably 1/6 or more and 5/6 or less of the thickness of the mounting surface of the plate. If the length W from the outer peripheral edge of the thin wall portion is less than 0.3 mm, a sufficient stress relaxation effect cannot be obtained, causing cracks. Moreover, what was formed in the part exceeding 1.0 mm does not have a sufficient stress relaxation effect, and will also reduce a mounting area. If the thickness T of the thin portion 3b is less than 1/6 of the thickness of the mounting surface of the aluminum plate, the strength of the aluminum plate may be reduced, and if it exceeds 5/6, the stress relaxation effect is not recognized.
[0038]
  Next, the present inventionNoAn example of a Ramics circuit board is shown in FIG.
[0039]
As shown in FIG. 3, the ceramic circuit board 4 of the present invention has a plurality of holes 5 formed on the inner side of the outer peripheral edge of the aluminum plate 3 opposite to the joint surface with the ceramic substrate 2. is there.
[0040]
As a preferred embodiment of the above-described ceramic circuit board of the present invention, the plurality of holes 5 are linearly formed along the outer peripheral edge of the aluminum plate 3, for example. The transverse shape of the hole may be circular as shown in FIG. 4 or rectangular as shown in FIG. Such a plurality of holes may be formed by etching, or may be formed by pressing using a mold. Thus, by forming a plurality of holes in a straight line, the stress concentration on the outer peripheral edge of the aluminum plate can be efficiently reduced.
[0041]
As the size of such a hole, when the hole is a circle as shown in FIG. 4, D is preferably 0.3 mm or more and 1.0 mm or less, where D is the diameter of the hole. Further, when L is the distance between the holes, L is preferably 0.3 mm or more and 1.0 mm or less. Furthermore, when the distance from the outer peripheral edge of the metal plate to the hole is Z, Z is preferably 0.3 mm or more.
[0042]
If the diameter of the hole is less than 0.3 mm, the stress cannot be sufficiently relaxed, and if it exceeds 1.0 mm, the strength of the aluminum plate is reduced and the mounting area is also reduced. If the distance between the holes is too large, the stress relaxation effect may not be sufficiently obtained. If it is too small, the aluminum plate may be deformed when the holes are processed. Further, if the distance Z from the outer peripheral edge of the metal plate to the outer peripheral edge of the hole is less than 0.3 mm, the stress relaxation effect may not be sufficient.
[0043]
The plurality of holes described above may be non-through holes 5a as shown in FIGS. 6 and 7, or may be through holes 5b as shown in FIG. For example, the non-through hole 5a can be easily formed by pressing or the like, which is effective for reducing the number of manufacturing steps. Further, when the DBA method is applied, the through hole 5b can also function as a discharge hole for gasified oxygen or the like without contributing to bonding.
[0044]
When the plurality of holes are non-through holes 5a, the shape in the depth direction may be a substantially uniform shape as shown in FIG. 6, or an inverted conical shape as shown in FIG. Also good.
[0045]
Next, another example of the ceramic circuit board of the present invention will be described.
[0046]
As shown in FIG. 9, the ceramic circuit board 6 of the present invention is such that a discontinuous groove 7 is formed on the inner side of the outer peripheral edge of the aluminum plate 3 opposite to the joint surface with the ceramic substrate 2. is there. By providing such a discontinuous groove 7, the stress generated at the outer peripheral edge of the aluminum plate 3 can be efficiently relaxed. Here, the inner side of the outer peripheral edge is a portion directed from the outer peripheral edge of the metal plate toward the center as shown in FIG. In the ceramic circuit board of the present invention, the discontinuous grooves are preferably formed linearly. By forming the discontinuous grooves in a straight line in this manner, stress concentration can be more efficiently mitigated.
[0047]
FIG. 10 is an enlarged view of a part of the ceramic circuit board 6 of the present invention. Here, W represents the width of the single groove, E represents the length of the single groove, and Z represents the distance from the outer peripheral edge of the single groove.
[0048]
  The shape of each single groove constituting a discontinuous groove, that is, the width W, length E, and distance from the outer peripheral edge of the single grooveZ isThe width W is 0.05 mm or more and 1.0 mm or less, the length E is 20 mm or less, and the distance Z from the outer peripheral edge is 0.3 mm or more.The
[0049]
When the width W is less than 0.05 mm, the stress cannot be sufficiently relaxed, and when it exceeds 1.0 mm, the strength of the aluminum plate is reduced and the mounting area is also reduced. Moreover, when the length E of each single groove exceeds 20 mm, there is a possibility that deformation of the aluminum plate cannot be sufficiently suppressed as the groove non-forming region decreases. Further, if the distance Z from the outer peripheral edge is less than 0.3 mm, a sufficient stress relaxation effect may not be obtained.
[0050]
Further, the longitudinal cross-sectional shape of the discontinuous grooves 7 may be substantially uniform in the depth direction as shown in FIG. 11, or may be an inverted triangle shape as shown in FIG. However, the depth H is preferably from 1/6 to 5/6 of the thickness of the mounting surface of the aluminum plate. If the depth H is less than 1/6 of the thickness of the mounting surface of the aluminum plate, the stress dispersion effect may be insufficient, and if the depth H exceeds 5/6 of the thickness of the mounting surface of the aluminum plate, It tends to cause a decrease in strength of the aluminum plate.
[0051]
Further, the ceramic substrate used for the ceramic circuit board of the present invention is preferably made of at least one material selected from the group consisting mainly of alumina, aluminum nitride and silicon nitride.
[0052]
  NextHalfAn embodiment of a conductor device will be described.
[0053]
  FIG.HalfIt is the figure which showed the external appearance of the conductor apparatus. In addition, FIG.HalfIt is the figure which showed the cross-sectional shape of the conductor apparatus.
[0054]
  HalfAs shown in FIG. 13, the conductor device 8 is bonded to an aluminum plate 3 bonded to a ceramic substrate 2 such as aluminum nitride via a solder layer 9 on a surface of the aluminum plate 3 where the ceramic substrate 2 is not bonded. In the semiconductor device 8 including the semiconductor element 10, a plurality of grooves 11 are provided on the surface of the aluminum plate 3 to which the semiconductor element 10 is bonded.
[0055]
Here, H indicates the depth of the groove formed in the aluminum plate, W indicates the width of the groove, and L indicates the distance between the grooves.
[0056]
Conventionally, when a semiconductor element is soldered to an aluminum plate, a gas is caught in the solder portion to form a solder nest. Since the solder nest present in the solder portion causes a thermal resistance failure, it is preferably removed.
[0057]
  thisIn the semiconductor device, by providing the groove 11 on the surface of the aluminum plate 3 on which the solder layer 9 is formed in this way, the gas that causes the formation of the solder nest is discharged from the groove 11 to suppress the generation of the solder nest. However, even if the solder nest is generated, the formation of the solder nest larger than the groove 11 can be suppressed by providing the groove 11. Therefore,thisIn the semiconductor device, it is possible to suppress the thermal resistance failure due to the solder nest, and to suppress variations in the thermal resistance and the like in each semiconductor device.
[0058]
The depth H of the groove formed in such an aluminum plate is 1/6 or more and 5/6 or less of the thickness of the aluminum plate, the width W is 0.05 mm or more and 1.0 mm or less, and the distance L between adjacent grooves is It is preferable that it is 0.05 mm or more and 5.0 mm or less.
[0059]
When the depth of the groove is less than 1/6 of the thickness of the aluminum plate, the gas discharge effect is reduced and solder nests are easily formed. When the depth of the groove exceeds 5/6 of the thickness of the aluminum plate, the strength of the aluminum plate It will cause a decline. Further, if the width W is less than 0.05 mm, the gas discharge effect is lowered, and solder nests are easily formed. If the width W exceeds 1.0 mm, the gas discharge effect is lowered and the strength of the aluminum plate is reduced. I will invite you. Further, if the gap L between the grooves is less than 0.05 mm, the strength of the substrate is lowered, and if the gap L exceeds 5.0 mm, the gas discharge effect is lowered, and a solder nest is formed. It becomes easy to be done.
[0060]
  MoreHalfThe ceramic substrate used for the conductor device is preferably composed mainly of at least one material selected from alumina, aluminum nitride, silicon nitride and the like. The metal plate mainly made of an aluminum plate is not particularly limited as long as the aluminum content is 50 wt% or more. High purity aluminum having a purity of 99% or more, Al—Mg alloy, Al—Mn alloy, Al—Si alloy Various aluminum alloy plates can be applied. Among them, it is particularly preferable to use an Al—Si alloy plate because an Al—Si alloy is easily eutectic bonded to various ceramics. The Si content is preferably 0.001 to 40 wt%. For example, in ceramics that do not contain Si as a main component, such as alumina and aluminum nitride, the Si content in the aluminum plate is preferably 5 to 30 wt%. Thus, in the ceramic containing Si as a main component, the Si content in the aluminum plate is preferably 0.01 to 15 wt%.
[0061]
  Less thanHalfAn example of a method for manufacturing a conductor device will be described.
[0062]
For example, an aluminum plate is bonded to a ceramic substrate made of aluminum nitride by the DBA method. Further, a plurality of grooves longer than the length of the semiconductor element are formed by a method such as etching in a portion to which the semiconductor element such as a Si pellet on the surface of the bonded aluminum plate to which the ceramic substrate is not bonded is to be bonded. A semiconductor element is bonded to the surface on which the groove is formed using solder. In this way, by joining the semiconductor element to the portion where the groove is provided in advance using the solder, it is possible to suppress the removal or growth of the solder nest generated in the solder portion and suppress the thermal resistance failure.
[0063]
In the ceramic circuit board of the present invention, an aluminum plate provided with grooves in advance by etching or pressing may be directly bonded to the ceramic substrate, or aluminum is melted and applied to the ceramic substrate, and then etched or the like. A groove may be formed and the semiconductor elements may be joined by soldering.
[0064]
【Example】
Next, specific examples of the present invention and evaluation thereof will be described.
[0065]
Reference Example 1,Example 12Comparative Example 1
Reference example 1
  An aluminum plate having a thickness of 0.5 mm and a purity of 99% or more was prepared, and the thickness of a portion from the outer peripheral edge portion of this aluminum plate to 1 mm was set to 0.25 mm by etching. Thereafter, this aluminum plate was directly bonded to an aluminum nitride substrate having a thickness of 0.7 mm to produce a ceramic circuit substrate.
[0066]
Example1
  An aluminum plate having a thickness of 0.5 mm and a purity of 99% or more was prepared, and a plurality of holes were provided inside the outer peripheral edge of the aluminum plate by etching. The hole diameter was 0.5 mm, the interval between the holes was 0.5 mm, and the edge of the hole was 0.5 mm from the outer peripheral edge. This aluminum plate was directly joined to an aluminum nitride substrate having a thickness of 0.7 mm to produce a ceramic circuit board.
[0067]
Example2
  An aluminum plate having a thickness of 0.5 mm and a purity of 99% or more was prepared, and a plurality of grooves were provided inside the outer peripheral edge of the aluminum plate by etching. The depth of the groove was 0.25 mm, the width of the groove was 0.05 mm, and the edge of the groove was 0.5 mm from the outer peripheral edge. This aluminum plate was directly joined to an aluminum nitride substrate having a thickness of 0.7 mm to produce a ceramic circuit board.
[0068]
Comparative Example 1
An aluminum plate having a thickness of 0.5 mm and a purity of 99% or more was prepared, and this aluminum plate was directly bonded to an aluminum nitride substrate having a thickness of 0.7 mm to produce a ceramic circuit board.
[0069]
  Produced as aboveReference Example 1,Example 12The ceramic circuit board of Comparative Example 1 was subjected to a thermal cycle test (TCT: 233K × 30 minutes → RT × 10 minutes → 398K × 30 minutes → RT × 10 minutes as one cycle, RT is room temperature). The stress distribution when this thermal cycle was applied was measured.
[0070]
  Reference examples,Example,andThe results of the comparative example are shown in FIGS.
[0071]
As is clear from each figure, any thin plate, hole, or groove provided inside the outer peripheral edge of the aluminum plate alleviates the stress generated at the outer peripheral edge, and stress near the outer peripheral edge of the aluminum plate. Can be seen to be lower.
[0072]
On the other hand, when the aluminum plate was not processed at all, it was found that a large stress was generated at the outer peripheral edge of the aluminum plate and there was a risk of occurrence of cracks and the like.
[0073]
Reference Examples 2-5Comparative Example 2
Reference Examples 2-5
  An aluminum plate having a thickness of 0.5 mm, a length of 3 cm × a width of 3 cm, and a purity of 99% or more was prepared, and a plurality of grooves were provided at the center of the aluminum plate as shown in FIG. The depth (H), width (W), length (E) and interval (L) of the grooves were adjusted as shown in Table 1. Moreover, the groove | channel was not provided in the part 5 mm from the both edges of the direction perpendicular | vertical to a groove direction.
[0074]
Furthermore, an aluminum nitride substrate was directly bonded to the surface of the aluminum plate where no groove was provided, and a Si pellet was bonded to the center of the surface where the groove was provided using solder to produce a semiconductor device.
[0075]
A Si pellet having a thickness of 0.5 mm and a length of 2 cm × width of 2 cm was used.
[0076]
Comparative Example 2
  An aluminum plate having a thickness of 0.5 mm, a length of 3 cm x a width of 3 cm, and a purity of 99% or more is used. Then, an aluminum nitride substrate was directly joined to produce a semiconductor device. Si pelletsReference Examples 2-5The same one used in the above was used.
[0077]
  Made in this wayReference Examples 2-5The thermal resistance of the semiconductor device of Comparative Example 2 was measured.
[0078]
  Reference Examples 2-5Table 1 shows the evaluation results of the thermal resistance in Comparative Example 2.
[0079]
[Table 1]

  As is clear from Table 1,Reference Examples 2-5Thus, it was found that the thermal resistance failure was suppressed in any case where the groove was provided on the joint surface with the Si pellet. In particular, it was found that when the groove depth, width, length, and interval were set to preferable values in the present invention, the thermal resistance failure was greatly suppressed.
[0080]
On the other hand, it was found that in Comparative Example 2 in which the Si pellet and the aluminum plate were joined without providing a groove on the joint surface of the aluminum plate with the Si pellet, a thermal resistance failure occurred.
[0081]
  based on the above resultsAIt was confirmed that by providing a plurality of grooves on the Si pellet joint surface of the ruminium plate, generation or growth of solder nests can be suppressed, and thermal resistance defects can be significantly suppressed.
[0082]
Reference Examples 6-8
  Reference example 1What changed the aluminum plate of Al to 10 wt% Si plateReference Example 6,Reference example 1What changed the aluminum nitride substrate of silicon to a silicon nitride substrateReference Example 7,Reference example 1The aluminum plate was changed to an Al-10wt% Si plate and the aluminum nitride substrate was changed to a silicon nitride substrate.Reference Example 8It was.
[0083]
For such a ceramic circuit board, the peel strength of the aluminum plate and the thermal cycle test (TCT) are stricter than usual with one cycle of 233 K × 30 minutes → RT × 10 minutes → 398 K × 30 minutes → RT × 10 minutes. Under the conditions, the presence or absence of cracks in the ceramic substrate when 1000 cycles and 2000 cycles were performed was confirmed.
[0084]
For comparison, the same measurement was performed on the ceramic circuit board of Comparative Example 1. The results are shown in Table 2.
[0085]
[Table 2]

  As shown in Table 2, it can be seen that the peel strength is improved when Si is contained in the aluminum plate.
[0086]
  Also, looking at the TCT test results,referenceIn the example, the test conditions were 233K x 30 minutes-> RT x 10 minutes-> 398 K x 30 minutes-> RT x 10 minutes Despite severe conditions than usual, cracks in the ceramic substrate were confirmed up to 1000 cycles Was not.
[0087]
On the other hand, some peeling was confirmed in the comparative example. This is because the stress relaxation is not performed because there is no thin part in the outer peripheral part of the aluminum plate. In addition, the notation of “somewhat” in the TCT test indicates that some cracking phenomenon has been confirmed.
[0088]
  Furthermore, when comparing an aluminum nitride substrate and a silicon nitride substrate, a silicon nitride substrate (Reference Examples 7 and 8It was found that those using) exhibited superior TCT test characteristics.
[0089]
【The invention's effect】
The ceramic circuit board of the present invention suppresses stress concentration on the outer peripheral edge of the metal plate by dispersing thermal stress and residual stress generated in the metal plate mainly made of aluminum when a cooling / heating cycle is added. Generation of cracks in the ceramic circuit board can be suppressed.
[0090]
In addition, the semiconductor device of the present invention can suppress the formation of solder nests in the solder used when bonding the semiconductor elements to the ceramic circuit board, and can suppress thermal resistance defects and peeling.
[Brief description of the drawings]
FIG. 1 is an external view showing an example when a thin portion is provided inside an outer peripheral edge of a metal plate.
FIG. 2 is a cross-sectional view showing an example in which a thin portion is provided inside the outer peripheral edge of a metal plate.
FIG. 3 is an external view showing an example when a hole is provided inside the outer peripheral edge of a metal plate.
4 is an enlarged plan view of a part of FIG. 3;
FIG. 5 is a plan view showing an example of a hole having a rectangular shape.
FIG. 6 is a cross-sectional view showing an example when a hole is provided inside the outer peripheral edge of a metal plate.
FIG. 7 is a cross-sectional view showing another example of the shape of the hole in the depth direction.
FIG. 8 is a cross-sectional view showing an example when a hole is a through hole.
FIG. 9 is an external view showing an example when discontinuous grooves are provided inside the outer peripheral edge of a metal plate.
FIG. 10 is an enlarged plan view of a part of FIG. 9;
FIG. 11 is a cross-sectional view showing an example of a cross-sectional shape of a groove.
FIG. 12 is a cross-sectional view showing another example of the cross-sectional shape of the groove.
FIG. 13HalfThe external view which shows an example of a conductor apparatus.
FIG. 14HalfSectional drawing which shows an example of a conductor apparatus.
FIG. 15 shows the results after the thermal cycle test.Reference example 1The figure showing stress distribution of.
FIG. 16 shows an example after the thermal cycle test.1The figure showing stress distribution of.
FIG. 17 Example after the implementation of a cooling cycle test2The figure showing stress distribution of.
FIG. 18Reference Examples 2-5Schematic which showed an example of the aluminum plate used for the.
[Explanation of symbols]
1 …… Ceramic circuit board
2 ... Ceramic substrate
3. Aluminum plate
3a …… Outer peripheral edge
3b …… Thin part
5 ... hole
7 …… Groove
9 …… Solder layer
10 …… Semiconductor element
11 …… Groove

Claims (6)

In a ceramic circuit board comprising a ceramic substrate and a metal plate that is directly bonded to the surface of the ceramic substrate and mainly made of aluminum,
The said metal plate has a some hole provided in the outer-periphery edge inner side of the surface on the opposite side to the joint surface with the said ceramic substrate, The ceramic circuit board characterized by the above-mentioned. Wherein the plurality of holes, a ceramic circuit board according to claim 1, characterized in that it is formed in a straight line at predetermined intervals along the outer peripheral edge of the metal plate. The plurality of holes have a diameter of 0.3 mm or more and 1.0 mm or less, a distance between adjacent holes of 0.3 mm or more and 1.0 mm or less, and an edge of the hole is an outer peripheral edge of the metal plate 3. The ceramic circuit board according to claim 1 , wherein the ceramic circuit board is provided at a portion separated by 0.3 mm or more from the ceramic circuit board. In a ceramic circuit board comprising a ceramic substrate and a metal plate that is directly bonded to the surface of the ceramic substrate and mainly made of aluminum,
The metal plate, the provided on the outer circumferential edge portion inner side opposite to the surface of the bonding surface of the ceramic substrate, have a plurality of discontinuous grooves along the outer edge portion, the discontinuous grooves, the The depth is 1/6 or more and 5/6 or less of the thickness of the portion to be the mounting surface of the metal plate, the width is 0.05 mm or more and 1.0 mm or less, and the edge of the groove is the outer peripheral edge of the metal plate A ceramic circuit board characterized in that the ceramic circuit board is provided in a part separated by 0.3 mm or more from the part . The ceramic substrate is alumina, at least one ceramic circuit board of any one of claims 1 to 4, characterized in that mainly a material selected from the group consisting of aluminum nitride and silicon nitride. The ceramic circuit board according to any one of claims 1 to 5 , wherein the metal plate mainly made of aluminum is an Al-Si alloy plate.

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