JP2018101763A - Power module substrate and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power module substrate that is not subject to design constraints and a production method thereof.SOLUTION: A power module substrate 10 includes a ceramic substrate 16, an upper copper circuit board 12, and a lower copper circuit board 18. The upper copper circuit board 12 and the lower copper circuit board 18 are joined to the ceramic board 16 via a brazing material 14. The upper copper circuit board 12 and the lower copper circuit board 18 have tapered portions in their outlines. The tapered portion has such a shape that the width in the horizontal direction is less than half of the height in the vertical direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power module substrate used in a semiconductor device capable of controlling a large current and a high voltage, and a production method thereof.

Among semiconductor elements, a power module substrate for supplying power has a relatively high calorific value, and examples of substrates on which this is mounted include AlN (aluminum nitride), Al ₂ O ₃ (alumina), and Si ₃ N _4. Ceramic substrates such as (silicon nitride) are often used. An active metal brazing method in which a metal circuit board is joined to one or both main surfaces of the ceramic substrate via a brazing material has been widely used. In particular, copper circuit boards have attracted attention because of their low electrical resistance, excellent electrical conductivity, and low cost.

  When manufacturing such a power module substrate, an operation of processing the brazing material and the metal circuit board into a desired shape may be performed, and an etching technique is sometimes used in the operation. For example, a metal circuit board having a desired shape is formed by applying a resist material having etching resistance to a metal circuit board in a desired shape and then etching the metal circuit board. .

  However, in the etching process, side etching that proceeds in the width direction as well as in the depth direction of the metal circuit board usually occurs. For this reason, when processing the metal circuit board into a desired shape, it is necessary to consider the influence of side etching, and as a result, there is a problem of design restrictions.

  Therefore, in the prior art, in the circuit board in which the metal circuit board is bonded to the main surface of the ceramic substrate, the metal circuit board has a trapezoidal ground conductor in the longitudinal section and a triangular section in the longitudinal section. There is one that employs a configuration in which a line conductor having a top portion whose height is lower than the upper surface of the ground conductor is used (see, for example, Patent Document 1). By adopting such a configuration, it is possible to realize a partly narrow pitch of the line conductor and the accompanying miniaturization, and it is inexpensive and small in size. It was said that it would be possible to mix them.

Japanese Patent No. 4484676

  However, in the above-described conventional technology, only an attempt is made to minimize the degree of malfunction when side etching occurs, and there is a sufficient attempt to actively suppress side etching itself. I could not say. Side etching is a phenomenon that inevitably occurs in the etching process, but originally it is preferable to suppress the side etching itself. If the generation of the side etching itself can be suppressed, even when performing the etching process, it becomes difficult to receive design restrictions, so it can be said that an attempt to suppress the generation of the side etching itself is very important.

  An object of the present invention is to provide a power module substrate having a configuration that is less susceptible to design restrictions, and a method for producing the power module substrate.

The power module substrate according to the present invention includes at least a ceramic substrate and a metal circuit board. A typical example of the material of the ceramic substrate is Si ₃ N ₄ (silicon nitride), but AlN (aluminum nitride), Al ₂ O ₃ (alumina), and other materials can also be used. The metal circuit board is bonded to the ceramic substrate via a brazing material. This metal circuit board has a taper part in the outline. The tapered portion has a shape in which the horizontal width is less than half the vertical height.

  When a metal circuit board or brazing material is processed by an etching process, the width and height of the tapered portion are almost equal due to the influence of side etching, and the inclination angle is about 45 degrees. With such a shape, it may be difficult to form a fine circuit pattern, and it may be difficult to form a wide top portion of the metal circuit board. In the present invention, since the taper portion has a shape in which the horizontal width is less than half the vertical height, it is easy to realize a fine circuit pattern, a wide top portion, and the like.

  The power module substrate production method according to the present invention is applied to a power module substrate in which a metal circuit board is bonded to a ceramic substrate via a brazing material, and includes at least a masking step, a patterning step, and an etching step. It is out. In the masking step, a self-adhesive etching resistant film is attached to the metal circuit board. In the patterning step, a patterning process corresponding to a circuit pattern having a desired shape is performed on the self-adhesive etching resistant film to remove areas other than the region corresponding to the circuit pattern in the self-adhesive etching resistant film. In the etching step, the region from which the self-adhesive etching resistant film has been removed is etched by spray etching.

  In such a production method, by performing spray etching on a region not covered with a self-adhesive etching resistant film, side etching is less likely to occur, and a metal circuit board or brazing material formed by the etching process It becomes easy for the inclined surface of the taper part in the outline part to approach perpendicularly. As a result, the taper part tends to have a shape in which the horizontal width is less than half the height in the vertical direction, more preferably about a quarter, and a fine circuit pattern, a wide top portion, etc. are realized. It becomes easy to do.

  In the above patterning step, it is preferable that a part of the metal circuit board is removed together with the self-adhesive etching resistant film by a laser. By removing the etched portion of the metal circuit board in advance before the etching process, the influence of side etching can be further reduced.

  According to the present invention, it is possible to realize a power module substrate having a configuration that is hardly subject to design restrictions.

It is a figure which shows the outline of the power module board | substrate which concerns on one Embodiment of this invention. It is a figure which shows the shape of the metal circuit board edge part in a power module board | substrate. It is a figure which shows an example of the etching process with respect to a power module board | substrate. It is a figure which shows an example of the etching process with respect to a power module board | substrate. It is a figure which shows the example of the laser patterning process with respect to a power module board | substrate. It is a figure which shows an example of the etching process with respect to a power module board | substrate. It is a figure which shows the outline of the film peeling mechanism in an etching process. It is a figure which shows the variation of the spray etching apparatus used for an etching process.

1A and 1B show an outline of a power module substrate 10 according to an embodiment of the present invention. The power module substrate 10 includes a ceramic substrate 16 having a thickness of about 1 to 10 mm mainly composed of Si ₃ N ₄ (silicon nitride). The upper circuit copper plate 12 having a thickness of about 0.5 to 4 mm is joined to the first main surface (the upper main surface in the drawing) of the ceramic substrate 16 via the brazing material 14. The brazing material is used for active copper bonding, and a known brazing material containing silver, copper, a binder, and the like can be used. Generally, the thickness of the brazing material is about 0.01 to 0.10 mm. The upper circuit copper plate 12 is configured to mount a semiconductor element and form an electrically conductive state.

  On the other hand, the lower circuit copper plate 18 is joined to the second main surface (lower main surface in the drawing) of the ceramic substrate 16 via the brazing material 14. The thickness of the lower circuit copper plate 18 is substantially the same as that of the upper circuit copper plate 12. The lower circuit copper plate 18 is configured to dissipate heat generated from the semiconductor elements mounted on the upper circuit copper plate 12. The configurations of the upper circuit copper plate 12 and the lower circuit copper plate 18 described here are merely examples, and the present invention is not limited to such a configuration.

  Next, characteristics of the shapes of the upper circuit copper plate 12 and the lower circuit copper plate 18 in the power module substrate 10 will be described with reference to FIG. As shown in the figure, both the upper circuit copper plate 12 and the lower circuit copper plate 18 have an edged shape with the end portions being nearly vertical.

  For example, in the upper circuit copper plate 12, the width (side etching width) D1 in the horizontal direction of the tapered portion formed by side etching is suppressed to less than half of the etching amount T1 in the vertical direction. Similarly, in the lower circuit copper plate 18, the width D2 in the horizontal direction of the tapered portion formed by side etching is suppressed to less than half of the etching amount T2 in the vertical direction. The width of the taper portion may be directly measured as the width projected on the horizontal plane. For example, the width of the uppermost position of the copper circuit board (Top width) is reduced by the width of the lowermost position of the copper circuit board (Bottom width). It is possible to obtain the value obtained by further dividing by 2.

  Normally, the side etching width D1 of the upper circuit copper plate 12 is substantially equal to the etching amount T1 in the vertical direction of the upper circuit copper plate 12, and the side etching width D2 of the lower circuit copper plate 18 is the vertical direction of the lower circuit copper plate 18. However, in this embodiment, the side etching width D1 and the side etching width D2 are suppressed by performing a process described later.

  Then, the production method of the power module board | substrate 10 is demonstrated using FIG. 3 (A)-FIG. 3 (C) and FIG. 4 (A)-FIG. 4 (C). First, as shown in FIGS. 3A and 4A, a masking film 20 is attached to each of the upper circuit copper plate 12 and the lower circuit copper plate 18. This masking film 20 is a self-adhesive etching resistant film. The thickness of the masking film 20 is about 0.05 mm to 0.20 mm.

  Self-adhesive type sticking has the feature that it can be peeled off with the adhesive force of the film or sheet itself without using an adhesive and can be peeled off, and there is no adhesive residue after peeling. . That is, the self-adhesive type sticking has a feature that it can be attached and detached reversibly. As the self-adhesive film or sheet, vinyl chloride resin (PVC), ethylene-vinyl acetate copolymer resin (EVA), polyethylene resin (PE), or the like can be used.

  In this embodiment, Achilles Hitack (soft vinyl chloride resin) manufactured by Achilles is used. However, as masking film 20, E-75M (polyethylene resin) and V-325 (soft vinyl chloride resin) manufactured by Sumilon, gel poly (polyolefin-based resin) manufactured by Panap, KT-V290 (polyethylene / EVA-based) from Tatsuta Chemical It is also possible to use a self-adhesive etching resistant film such as a resin, and it is not limited to the films listed here.

  Subsequent to the application of the masking film 20, the patterning process shown in FIGS. 3B and 4B is performed. Here, the masking film 20 is processed into a desired circuit shape using a laser patterning apparatus capable of outputting a picosecond laser.

Thereafter, as shown in FIGS. 3C and 4C, an etching process is performed in which the portion where the masking film 20 is peeled is brought into contact with the etching solution. The upper circuit copper plate 12, the lower circuit copper plate 18, and the brazing material 14 are etched by different etching solutions. In this embodiment, the etching process for the upper circuit copper plate 12 and the lower circuit copper plate 18 uses an etching solution in which ferric chloride solution and hydrochloric acid are mixed at a certain ratio. An etching solution in which ammonium fluoride (NH ₄ F), ammonium hydrogen fluoride (NH ₄ ) HF ₂ , and hydrogen peroxide solution (H ₂ O ₂ ) are mixed is used. However, the composition of the etching solution used for etching the upper circuit copper plate 12, the lower circuit copper plate 18, and the brazing material 14 is not limited to these.

  What is characteristic in this embodiment is that the upper circuit copper plate 12 and the lower circuit copper plate are further added to the laser patterning shown in FIGS. 3B and 4B in addition to the normal process of removing the masking film 20. 18 is cut by a laser patterning device. For example, as shown in FIG. 5 (A), by cutting a part of the upper circuit copper plate 12 and the lower circuit copper plate 18 by laser processing, the amount required to be etched by the etching process is reduced, thereby reducing the influence of side etching. It becomes possible to do.

  Ideally, as shown in FIG. 5 (B), the laser patterning apparatus should cut the upper circuit copper plate 12 and the lower circuit copper plate 18 to the edge of the brazing material 14. However, in this case, it may be difficult to set the focal point of the laser, and there is a risk that the laser reaches the ceramic substrate 16 and contaminates the ceramic substrate. Therefore, in practice, as shown in FIG. 5C, it is preferable to set the focal point of the laser at the center of the plate thickness, preferably at a position where about 3/4 of the plate thickness can be cut. In setting the focal point, it is necessary to pay attention so that the masking film 20 is not too far from the masking film 20 and the masking film 20 which is the original purpose cannot be properly peeled off. In addition to setting the focus, it is important to set preferable processing conditions each time by appropriately adjusting the laser irradiation amount, processing speed, and the like.

  Moreover, the side etching width D1 and the side etching width D2 can also be suppressed by using a spray etching apparatus 100 as shown in FIG. The spray etching apparatus 100 includes an introduction unit 112, a pretreatment chamber 114, etching chambers (115, 116), cleaning chambers (117, 118), a peeling chamber 120, and a discharge unit 122. A partition wall having a slit-like opening through which the power module base material 124 can pass is disposed between these parts, and the power module base material 126 is separated from the introduction part 112 by a plurality of transport rollers 126. Then, it is conveyed to the discharge unit 122.

  In this embodiment, as the power module base material 124 processed by the spray etching apparatus 100, a power module substrate that can be chamfered (3 × 3) is used, but is not limited to this configuration. . Moreover, although the conveyance path is comprised by the some conveyance roller 126, you may make it comprise the conveyance path which adopted the belt conveyor.

  The introduction part 112 has an open top surface and is configured to receive the power module base material 124 that is subjected to the etching process by the spray etching apparatus 100. Usually, the power module base material 124 to be processed is placed on the transport roller 26 of the introduction unit 112 by an operator or a robot. The pretreatment chamber 114 is configured to perform a pretreatment for an etching process on the power module base material 124. In this embodiment, the surface of the power module base material is pickled with sulfuric acid in the pretreatment chamber 14. However, it is possible to perform water cleaning, degreasing, other acid cleaning, alkali cleaning, and the like in the pretreatment chamber 114. If the pretreatment is not necessary, the pretreatment chamber 114 itself is removed from the spray etching apparatus. It is also possible to omit from 100.

  The etching chamber 115 and the etching chamber 116 are each configured to perform an etching process on the power module base material 124. In the etching chamber 115, the first copper plate 12 and the second copper plate 18 are etched. In this embodiment, in the etching chamber 115, ferric chloride solution and hydrochloric acid are mixed at a certain ratio, and an etching solution that is appropriately replenished with pure water or hydrochloric acid is sprayed from the spray nozzle to the power module base material 124. .

  On the other hand, the brazing material is etched in the etching chamber 116. In this embodiment, in the etching chamber 116, an etching solution in which ammonium fluoride (NH 4 F), ammonium hydrogen fluoride, and hydrogen peroxide water are appropriately mixed is sprayed from the spray nozzle to the power module base material 124.

  The cleaning chamber 118 is configured to clean the power module base material 124 with cleaning water.

  The peeling chamber 120 is configured to automatically peel the masking film 20 (self-adhesive etching resistant film) attached to the power module base material 124.

  The peeling chamber 120 is disposed downstream of the etching chambers 115 and 116 and the cleaning chambers 117 and 118 in the transfer path. The peeling chamber 120 includes a peeling unit 200 that peels off the masking film 20 attached to the power module base material 124. As shown in FIG. 7, the peeling unit 200 includes a peeling sheet 202, a supply roll 204, a take-up roll 206, a pressure roll 208, and a tension roll 210.

  The peeling sheet 202 is for peeling off the masking film 20 attached to the power module base material 124, and in this embodiment, an adhesive sheet (polyester adhesive tape No. 315) manufactured by Nitto Denko is used. The structure of the peeling sheet 202 is not particularly limited as long as the adhesive strength falls within a desired range, and cloth made of fine fibers of nylon or polyester, paper waste, or other materials are used. It is possible.

  The supply roll 204 is configured to wind and store the peeling sheet 202 supplied to the peeling position. The winding roll 206 is configured to collect the used peeling sheet 202 that has been peeled off at the peeling position together with the masking film 20. The pressure roll 208 is configured to press the peeling sheet 202 in the direction of the power module base material 124. The tension roll 210 is provided to fold the peeling sheet 202 in an effectively stretched state.

 The peeling sheet 202 pressed against the power module base material 124 by the pressure roll 208 at the peeling position adheres and removes the masking film 20 attached to the power module base material 124. If the adhesive force between the peeling sheet 202 and the masking film 20 is stronger than the adhesive force between the masking film 20, the upper circuit copper plate 12 and the lower circuit copper plate 18, the masking film 20 is attached to the upper circuit copper plate 12 and the lower circuit copper plate 12. It becomes possible to move to the peeling sheet 202 side from the side circuit copper plate 18 side.

  The adhesive strength of the self-adhesive film suitably used in the present invention by the 180-degree peeling method is generally in the range of 0.1 N / width 25 mm to 3.2 N / width 25 mm. In this embodiment, Nitto Denko's polyester adhesive tape No. By using 315 for the peeling sheet 202, the masking film 20 is preferably automatically peeled off. The pressure-sensitive adhesive sheet used for the peeling sheet 202 is not necessarily limited to this, and any sheet having an adhesive strength of about 1.35 N / 10 mm can be used as the peeling sheet 202.

  Furthermore, the applicant's experiment clearly shows that the peeling treatment can be performed more smoothly by bringing the aqueous solution into contact with a 5 to 20% by weight sodium hydroxide aqueous solution for about 5 to 20 minutes before the peeling treatment. It has become. The reason is that the aqueous solution of sodium hydroxide penetrates between the masking film 20 and the upper circuit copper plate 12 and the lower circuit copper plate 18 to reduce the adhesive force between them, while impurities on the surface of the masking film 20 It is considered that this is because the adhesive force between the peeling sheet 202 and the masking film 20 is increased by removing the dirt.

  In an apparatus that performs single-wafer type continuous processing such as the spray etching apparatus 100, for example, as shown in FIG. It is preferable to provide an intermediate processing chamber 130 that is in contact with 124 and a cleaning chamber 140 in which sodium hydroxide is washed away from the power module base material 124. A structure in which sodium hydroxide is sprayed can also be employed. In this case, the power of the sodium hydroxide solution is set so that the masking film 20 and the upper circuit copper plate 12 and the lower circuit copper plate 18 can easily enter. It is preferable to adopt a configuration in which the sodium hydroxide aqueous solution is sprayed from the horizontal direction or the oblique direction with respect to the module base material 124.

  Since the masking film 20 is a self-adhesive film in which no pressure-sensitive adhesive remains, the masking film 20 can be reliably peeled off by a peeling process. When the peeling process is not automatically performed as in this embodiment, the peeling process may be performed manually. Even in that case, the self-adhesive film in which the adhesive does not remain contributes to the improvement of workability.

  When the sensor (not shown) detects that the power module base material 124 has reached the peeling position in the peeling chamber 120, the winding roll 206 starts winding the peeling sheet 202, so the power module base material is always supplied. It contacts the clean peeling sheet 202 supplied from the roll 204. As a result, it becomes possible to prevent the power module base material 124 from being damaged during the peeling process. Here, the peeling efficiency by the peeling sheet 202 is arranged by arranging the supply roll 204 and the take-up roll 206 so that the peeling sheet 202 advances in the same direction (forward direction) as the conveying direction of the power module base material 124 at the peeling position. However, the present invention is not limited to this configuration.

  A cleaning chamber 120 is disposed downstream of the peeling chamber 118, and the peeled power module base material 124 is guided to the cleaning chamber 120. The cleaning chamber 120 includes a water shower nozzle for washing the power module base material 124 and an air knife for draining the power module base material 124. The power module base material is stored in the cleaning chamber 120 as necessary. Washed with water. Note that in the cleaning chamber 120, when cleaning using a cleaning liquid instead of water is necessary, such cleaning may be appropriately performed.

  The discharge unit 122 at the rear stage of the cleaning chamber 120 is disposed on the most downstream side of the transport path, and is configured to open upward. The power module base material 124 that has been subjected to the etching process and the peeling process in the spray etching apparatus 100 is transported to the discharge unit 122 and is collected from above the transport roller 126 by an operator or a robot.

  By using the spray etching apparatus 100, the amount of side etching can be suppressed as compared with the case of dipping in an etching solution. In addition, it is possible to reduce the time required for etching the brazing material, compared with the case of dipping in an etching solution.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

10-Power module board 12-Upper copper circuit board 14-Braze material 16-Ceramics board 18-Lower copper circuit board 20-Masking film 100-Spray etching device 124-Power module base material 200-Peeling unit

Claims (3)

A ceramic substrate;
A metal circuit board bonded to the ceramic substrate via a brazing material, the metal circuit board having a tapered portion at the contour thereof;
Comprising at least
The taper portion has a shape in which the horizontal width is less than half the vertical height. A method for producing a power module substrate in which a metal circuit board is bonded to a ceramic substrate via a brazing material,
A masking step of attaching a self-adhesive etching resistant film to the metal circuit board;
A patterning step for removing a region other than the region corresponding to the circuit pattern in the self-adhesive etching resistant film by performing a patterning process corresponding to a circuit pattern of a desired shape on the self-adhesive etching resistant film;
An etching step of etching the region from which the self-adhesive etching resistant film has been removed by a spray etching process;
A method for producing a power module substrate including at least   3. The method for producing a power module substrate according to claim 2, wherein in the patterning step, a part of the metal circuit board is removed together with the self-adhesive etching resistant film by a laser.

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