JP6398243B2 - Power module substrate manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate used in a semiconductor device that controls a large current and a high voltage.

  As a method for manufacturing this type of power module substrate, for example, as described in Patent Document 1 or Patent Document 2, laser light is applied to the surface of a ceramic base material having a wide area on which a plurality of power module substrates can be formed. , A scribe line (dividing groove) is provided in advance so as to divide the ceramic base material into the size of each substrate, and the ceramic base material is divided along the scribe line into individual pieces. A method for manufacturing a power module substrate is known.

Patent Document 2 describes that when a scribe line is formed by laser processing, a heat-denatured layer that is vitrified (amorphized) by the heat of laser light is formed on the scribe line. Yes. In addition, the vitrified heat-denatured layer is cooled after laser processing to cause minute cracks, and when the power module substrate is used in a thermal cycle, the ceramic substrate is cracked starting from the minute cracks. It is described.
In this case, in Patent Document 2, it is proposed to remove the vitrified heat-denatured layer by performing an etching process using fluorinated nitric acid. By removing the heat-denatured layer in this way, It is described that it is possible to suppress the occurrence of cracks in the ceramic substrate starting from minute cracks generated in the modified layer.

Japanese Patent No. 2000-86367 JP 2008-198635 A

  However, in the power module substrate, when the electroless plating process is performed on the power module substrate on which the circuit layer or the metal layer is formed, the plating is deposited on the scribe line. However, it is a new problem that the withstand voltage of the power module substrate is lowered, that is, the insulation performance is deteriorated due to the induction of electric discharge at that portion.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the board | substrate for power modules which can ensure favorable insulation performance.

As a result of intensive studies on a method for manufacturing a power module substrate, the present inventor has obtained the following knowledge.
In a method for manufacturing a power module substrate in which a scribe line is formed by laser processing, as described in Patent Document 2, a heat-denatured layer that is vitrified by the heat of laser light is formed. In this regard, Patent Document 2 describes that the vitrified heat-denatured layer can be removed by etching treatment with hydrofluoric acid, but the ceramic base material before brazing and joining of the ceramic base material and the metal layer is described. When etching is performed with hydrofluoric acid, fluorine remains in the ceramic base material, which causes peeling between the ceramic substrate and the metal layer when the power module is subjected to a thermal cycle, reducing joint reliability. It was.
On the other hand, it was found that when the ceramic base material and the metal layer (circuit layer) were brazed and joined and then etched, the heat-modified layer could not be completely removed. In this case, if the electroless plating process is performed on the power module substrate, the remaining heat-denatured layer may adhere to the plating. It was found that the voltage property was lowered.
Therefore, in the method for manufacturing a power module substrate of the present invention, the problem was solved by the following method.

The method for manufacturing a power module substrate of the present invention includes dividing the ceramic base material into a plurality of ceramic substrates along a scribe line formed on the ceramic base material formed of a ceramic material containing aluminum, A method of manufacturing a plurality of power module substrates having a metal layer laminated thereon, wherein the ceramic base material is irradiated with laser light to form the scribe line, and the scribe line is formed. A cleaning step of cleaning the ceramic base material with an etching solution for aluminum, a joining step of brazing and joining a metal plate for forming the metal layer to the ceramic base material after the cleaning step, and joining to the ceramic base material An etcher that forms a pattern by etching a metal plate If, comprising a dividing step of dividing along the ceramic base material after the etching step to the scribe line, and a plating step of applying electroless plating to the metal layer after the splitting step.

Before the step of joining the ceramic base material and the metal plate, that is, before the ceramic base material on which the scribe line is formed is exposed to a high temperature, a cleaning step for cleaning the ceramic base material with an aluminum etching solution is provided. Thus, the heat-denatured layer formed on the scribe line can be easily removed.
Therefore, when the electroless plating process is performed on the power module substrate, it is possible to avoid the plating from adhering to the edge of the ceramic substrate, and thus it is possible to ensure good insulation performance.
In addition, when it is going to remove the heat-denatured layer formed in the scribe line of the ceramic base material after brazing joining of the ceramic base material and the metal plate, it becomes difficult to completely remove the heat-denatured layer. In this case, a part of the heat-denatured layer formed on the scribe line is changed to a more stable oxide by being exposed to a high temperature during brazing joining of the ceramic base material and the metal plate, It is thought that the factor is that it becomes difficult to dissolve in the treatment liquid.

Further, the method for manufacturing a power module substrate according to the present invention divides the ceramic base material into a plurality of ceramic substrates along a scribe line formed in the ceramic base material formed of a ceramic material containing aluminum, and A method of manufacturing a plurality of power module substrates in which a metal layer is laminated on a ceramic substrate, wherein the ceramic base material is irradiated with laser light to form the scribe line, and the scribe line is formed. A dividing step of dividing the ceramic base material along the scribe line to form a plurality of ceramic substrates, a cleaning step of cleaning the divided ceramic substrates with an etching solution for aluminum, and a step after the cleaning step A metal layer is brazed and bonded to the ceramic substrate. Comprising a joining step for forming, and a plating step of applying electroless plating to the metal layer after the bonding step.

  As described above, after the ceramic base material is divided, it is possible to provide a cleaning step and a metal plate joining step. In this case, a cleaning step is provided before the ceramic substrate and metal plate joining step. Thus, the heat-denatured layer formed on the scribe line can be easily removed.

In the method for manufacturing a power module substrate according to the present invention, the aluminum etching solution is an aqueous solution mainly composed of iron chloride, copper chloride or sodium hydroxide.
By using an aqueous solution containing iron chloride, copper chloride or sodium hydroxide as a main component for the etching solution for aluminum, the heat-denatured layer formed on the scribe line can be easily removed.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to ensure favorable insulation performance of the board | substrate for power modules.

It is a flowchart explaining the manufacturing method of the board | substrate for power modules of 1st Embodiment of this invention. It is sectional drawing which shows the power module using the board | substrate for power modules. It is a figure explaining the manufacturing process of the manufacturing method of the board | substrate for power modules of 1st Embodiment. It is a flowchart explaining the manufacturing method of the board | substrate for power modules of 2nd Embodiment of this invention. It is a figure explaining the manufacturing process of the manufacturing method of the board | substrate for power modules of 2nd Embodiment. It is sectional drawing explaining the board | substrate for power modules to which this invention is applied.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 shows a power module 1 using a power module substrate 3 manufactured by the method for manufacturing a power module substrate of the present invention.
The power module 1 includes a power module substrate 3, an electronic component 4 such as a semiconductor chip mounted on the surface of the power module substrate 3, and a heat sink 5 attached to the back surface.

  The power module substrate 3 includes a ceramic substrate 2, a circuit layer 6 laminated on one surface of the ceramic substrate 2, and a metal layer 7 laminated on the other surface of the ceramic substrate 2. The substrate 2, the circuit layer 6 and the metal layer 7 are brazed and joined. The electronic component 4 is soldered to the surface of the circuit layer 6 of the power module substrate 3, and the heat sink 5 is bonded to the surface of the metal layer 7.

The ceramic substrate 2 is formed of a ceramic material containing aluminum such as AlN (aluminum nitride) or Al ₂ O ₃ (alumina). The circuit layer 6, the metal layer 7, and the heat sink 5 are made of pure aluminum or aluminum alloy, pure copper or copper alloy, and pure aluminum or aluminum alloy with a purity of 99.00% by mass or more, oxygen-free copper, tough pitch copper, or the like It is desirable to form with pure copper or copper alloy. The ceramic substrate 2 and the circuit layer 6 and the metal layer 7 are, when the circuit layer 6 and the metal layer 7 are formed of pure aluminum or an aluminum alloy, Al-Si, Al-Ge, Al-Cu, It brazes and joins with the brazing material of an alloy such as Al-Mg or Al-Mn. When the circuit layer 6 and the metal layer 7 are pure copper or a copper alloy, they are joined by active metal brazing using Ag—Cu—Ti or Ag—Ti brazing material.

  The heat sink 5 has an appropriate shape such as a flat plate, one in which a large number of pin-shaped fins are integrally formed by hot forging or the like, and one in which strip-like fins are formed in parallel by extrusion. Can be adopted.

Next, a method for manufacturing the power module substrate 3 configured as described above will be described. The method for manufacturing a power module substrate according to the first embodiment includes a plurality of manufacturing steps as shown in FIG.
(Laser processing process)
First, as shown in FIG. 3A, a scribe line 21 is formed on the surface of a plate-shaped ceramic base material 20. As shown in FIG. 3A, the scribe line 21 is formed by cutting the surface of the ceramic base material 20 by irradiating the laser beam L. At this time, a heat-denatured layer 22 that is vitrified by the heat of the laser beam is formed on the scribe line 21. The heat-denatured layer 22 is formed by mixing amorphous aluminum oxide, aluminum free substance, and the like, and is formed to a depth of about 1 μm to 40 μm.
In the laser processing step, the scribe line 21 can be processed using, for example, a CO ₂ laser, a YAG laser, a YVO 4 laser, a YLF laser, or the like.

(Washing process)
Next, although not shown, the ceramic base material 20 on which the scribe line 21 is formed is cleaned by immersing it in an aluminum etching solution. The etching solution for aluminum is an aqueous solution mainly composed of iron chloride, copper chloride or sodium hydroxide, and one to which various additives are added can also be used. In addition, the etching liquid for aluminum can use the same thing as the etching liquid used at the etching process mentioned later, when forming the circuit layer 6 and the metal layer 7 with a pure aluminum or aluminum alloy.
Then, by immersing the ceramic base material 20 in the etching solution for aluminum, as shown in FIG. 3B, the heat-denatured layer 22 formed on the scribe line 21 of the ceramic base material 20 is removed. The temperature and immersion time of the aluminum etching solution at this time are set to conditions under which the heat-denatured layer 22 having a depth of about 1 to 40 μm is removed.

(Joining process)
And as shown in FIG.3 (c), the metal plates 60 and 70 used as the circuit layer 6 and the metal layer 7 are brazed and joined to the ceramic base material 20 after a washing | cleaning process. Specifically, the metal plates 60 and 70 are laminated on both surfaces of the ceramic base material 20 with the brazing material foil interposed therebetween, and these laminated bodies are heated in a vacuum while being pressed, thereby producing ceramics. A joined body 30 is formed by brazing the base material 20 and the metal plates 60 and 70 together.

(Etching process)
Next, the patterns of the circuit layer 6 and the metal layer 7 are formed by etching the metal plates 60 and 70 bonded to the ceramic base material 20 of the bonded body 30. As a result, as shown in FIG. 3D, the ceramic base material 20 is provided with the circuit layer 6 and the metal layer 7 in each region partitioned by the scribe line 21.

(Division process)
Then, by dividing the ceramic base material 20 along the scribe line 21 by a cutting means such as a dicing device or a substrate splitting device, the ceramic base material 20 is singulated as shown in FIG. A plurality of power module substrates 3 are manufactured.

(Plating process)
Finally, although not shown in the drawing, each power module substrate 3 is subjected to electroless plating treatment such as gold plating, silver plating, nickel plating, etc., so that the electroless plating is formed on the circuit layer 6 and the metal layer 7. The module substrate 3 can be manufactured.

As described above, in the method for manufacturing the power module substrate of the present embodiment, the ceramic base material 20 on which the scribe line 21 is formed is joined before the ceramic base material 20 and the metal plates 60 and 70 are joined. The heat-denatured layer 22 formed on the scribe line 21 can be easily removed by providing a cleaning step of cleaning with the ceramic base material 20 and the aluminum etching solution before being exposed to the high temperature during the adhesive bonding. it can.
Therefore, when the electroless plating process is performed on the power module substrate 3, it is possible to avoid the plating from adhering to the edge of the ceramic substrate 2 (where it was the scribe line 21). Can be secured.

  In the case where the heat-modified layer 22 formed on the scribe line 21 of the ceramic base material 20 is to be removed by brazing between the ceramic base material 20 and the metal plates 60 and 70, the heat-modified layer It becomes difficult to completely remove 22. In this case, a part of the heat-denatured layer 22 formed on the scribe line 21 is exposed to a high temperature at the time of brazing and joining the ceramic base material 20 and the metal plates 60 and 70, so that a more stable oxide. The change is considered to be a factor.

FIG. 4 shows a manufacturing process of a method for manufacturing a power module substrate according to the second embodiment of the present invention.
In the method for manufacturing the power module substrate of the first embodiment (see FIG. 1), the cleaning step is provided before the dividing step of the ceramic base material 20, but the method for manufacturing the power module substrate of the second embodiment. In FIG. 2, a cleaning process and a joining process of the metal plates 60 and 70 are provided after the dividing process of dividing the ceramic base material 20 along the scribe line 21. Note that in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the method for manufacturing the power module substrate of the second embodiment, first, as shown in FIG. 5A, after the scribe line 21 is formed on the surface of the plate-shaped ceramic base material 20 (laser processing step), As shown in FIG. 5B, the ceramic base material 20 is divided into a plurality of ceramic substrates 2 by dividing the ceramic base material 20 along the scribe line 21 (a dividing step).

Then, each ceramic substrate 2 is cleaned by immersing it in an aluminum etching solution, and the thermally denatured layer 22 is removed from the ceramic substrate 2 as shown in FIG. 5C (cleaning step). The power module substrate 3 in which the circuit layer 6 and the metal layer 7 are laminated on the ceramic substrate 2 by brazing a metal plate having a pattern formed by pressing to the ceramic substrate 2 from which the heat-denatured layer 22 has been removed. Is formed (joining step). It is also possible to form a circuit pattern by etching after the metal layer to be the circuit layer 6 and the metal layer 7 is brazed to the ceramic substrate 2.
Finally, by applying electroless plating to each power module substrate 3, the power module substrate 3 in which the electroless plating is formed on the circuit layer 6 and the metal layer 7 can be manufactured.

Next, examples of the present invention and comparative examples performed for confirming the effects of the present invention will be described.
As an example of the present invention and a comparative example, a ceramic substrate 2 made of AlN having a thickness of 0.635 mm, a circuit layer 6 made of 4N-Al having a thickness of 0.6 mm, and a metal layer 7 made of 4N-Al having a thickness of 0.6 mm; A sample of the power module substrate 3 was fabricated by bonding the above with an Al—Si brazing material.
The samples of the present invention and the comparative example were prepared by using a ceramic base material on which a scribe line 21 having a depth of 100 μm (the thickness of the heat-denatured layer was 30 μm) was formed using a CO ₂ laser having a wavelength of 10 μm. Also, at the stage before brazing and joining of the metal plate 60 to be the circuit layer 6 and the metal plate 70 to be the metal layer 7, cleaning was performed by dipping in a cleaning solution composed of an aqueous solution of the main components shown in Table 1. Table 1 shows the cleaning conditions for each sample.

Then, after the cleaning process, the metal plates 60 and 70 were brazed and joined to the ceramic base material 20, and an etching process was performed to form patterns of the circuit layer 6 and the metal layer 7. The planar size of the circuit layer 6 and the metal layer 7 is 25 mm × 15 mm with respect to the planar size 26.6 mm × 16.6 mm of the ceramic substrate 2 partitioned by the scribe line 21, and the circuit starts from the edge of the ceramic substrate 2. A rectangular pattern was formed so that the distance to the edge of the layer 6 and the metal layer 7 was 0.8 mm. Further, the circuit layer 6 and the metal layer 7 were subjected to electroless nickel plating, and the power module substrate 3 of each sample was produced.
For the sample of Comparative Example 2, since the ceramic base material 20 was not cleaned, the “cleaning liquid” and “cleaning condition” columns in Table 1 are indicated by “−”.

With respect to each sample of the power module substrate 3 thus produced, an alternating voltage was applied stepwise from 1 kV to 100 V between the circuit layer 6 and the metal layer 7 to reach a cutoff current. The voltage value (withstand voltage value) was measured. As a measuring instrument, a withstand voltage tester (TOS5050 manufactured by Kikusui Electronics Co., Ltd.) was used, and the cut-off current value was set to 1 mA.
Table 1 shows the results.

As can be seen from Table 1, Example 1 of the present invention, which was cleaned using an aluminum etchant mainly composed of iron chloride (FeCl ₃ ), and an aluminum etchant composed mainly of copper chloride (CuCl ₂ ) were used. In the sample of Inventive Example 2 that was cleaned in this manner, the withstand voltage value was higher than that of Comparative Example 1 that was cleaned with hydrofluoric acid (HNO ₃ + NH ₄ HF ₂ ) and Comparative Example 2 that was not cleaned. As a result, it was confirmed that the insulation performance of the power module substrate could be secured satisfactorily.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, the power module substrate is described in which the circuit layer 6 and the metal layer 7 are laminated on the ceramic substrate 2 as shown in FIG. is not. The method for manufacturing a power module substrate of the present invention can also be applied to a power module substrate comprising a ceramic substrate and a circuit layer. As shown in FIG. 6, the circuit layer 6A comprises a copper plate 61 and an aluminum plate 62. The present invention can be applied to various configurations such as the power module substrate 3A formed by the joined laminated circuit layer 6A.

  Further, the processing of the scribe line 21 on the ceramic base material 20 is not limited to the case where it is performed only on one side of the ceramic base material 20 as in the present embodiment, and the scribe lines 21 are formed on both sides of the ceramic base material 20. The case where it provides is also included.

DESCRIPTION OF SYMBOLS 1 Power module 2 Ceramic substrate 3, 3A Power module substrate 4 Electronic component 5 Heat sink 6, 6A Circuit layer 7 Metal layer 20 Ceramic base material 21 Scribe line 22 Thermally modified layer 60, 70 Metal plate 61 Copper plate 62 Aluminum plate

Claims (3)

A power module substrate in which a ceramic layer is divided into a plurality of ceramic substrates along a scribe line formed on a ceramic substrate formed of a ceramic material containing aluminum , and a metal layer is laminated on the ceramic substrate. A method of manufacturing a plurality of methods,
A laser processing step of irradiating the ceramic base material with a laser beam to form the scribe line;
A cleaning step of cleaning the ceramic base material on which the scribe line is formed with an etching solution for aluminum;
A joining step of brazing and joining a metal plate forming the metal layer to the ceramic base material after the cleaning step;
An etching step of forming a pattern by etching a metal plate bonded to the ceramic base material;
A dividing step of dividing the ceramic base material along the scribe line after the etching step;
And a plating step of performing electroless plating on the metal layer after the dividing step. A power module substrate in which a ceramic layer is divided into a plurality of ceramic substrates along a scribe line formed on a ceramic substrate formed of a ceramic material containing aluminum , and a metal layer is laminated on the ceramic substrate. A method of manufacturing a plurality of methods,
A laser processing step of irradiating the ceramic base material with a laser beam to form the scribe line;
A dividing step of dividing the ceramic base material on which the scribe line is formed along the scribe line to form a plurality of the ceramic substrates;
A cleaning step of cleaning the divided ceramic substrate with an etching solution for aluminum;
A bonding step of brazing and bonding a metal plate to the ceramic substrate after the cleaning step to form a metal layer;
And a plating step of performing electroless plating on the metal layer after the joining step.   3. The method for manufacturing a power module substrate according to claim 1, wherein the aluminum etching solution is an aqueous solution mainly composed of iron chloride, copper chloride, or sodium hydroxide. 4.

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