JP7047493B2 - Ceramic substrate manufacturing method and circuit board manufacturing method - Google Patents

Description

The present invention is a method of manufacturing a ceramic substrate used for a power module substrate or the like by forming a break line on a ceramic plate and dividing by the black line, and a circuit of a power module substrate or the like using the ceramic substrate. Regarding the method of manufacturing a substrate.

In the power module substrate, a circuit layer made of a metal plate such as aluminum or copper is laminated on one surface of a ceramic substrate such as aluminum nitride, silicon nitride, or alumina, and aluminum or the like having excellent thermal conductivity is also laminated on the other surface. It is formed by laminating heat dissipation layers made of metal plates.
When manufacturing this power module board, break lines are formed vertically and horizontally on a ceramic plate having a size capable of forming a plurality of power module boards, and a circuit layer is formed in a region partitioned by the break lines. And the heat radiating layer is joined in a laminated state, and then the circuit layer is plated, and then the ceramic plate is separated from the break line to be individualized.

This breakline is generally processed by irradiating it with a laser beam, but the heat of the laser beam forms a modified layer on the surface of the breakline. In the case of a metal component constituting the ceramic plate, for example, an aluminum nitride plate, the modified layer is obtained by removing nitrogen and precipitating aluminum. For this reason, the break line is also plated (for example, nickel plating) by the subsequent electroless plating treatment, which may impair the performance as an insulating substrate. Therefore, the modified layer is removed before the plating treatment. There is a need to.
Conventionally, as a method for removing a modified layer generated by such laser processing, for example, as shown in Patent Document 1, an etching process is performed after the laser processing.

Japanese Unexamined Patent Publication No. 2008-198635

However, in the etching process, the portion other than the break line is also immersed in the etching solution and etched. In particular, if the etching process is performed after the circuit layer is formed, the surface of the circuit layer may be melted, resulting in dimensional defects and shape defects.
In addition to laser processing, there is also a method of forming a break line with, for example, a diamond cutter, but the linearity when divided is inferior to that formed by laser processing, and chipping is likely to occur.

The present invention has been made in view of such circumstances, and an object of the present invention is to form a break line without a modified layer on a ceramic plate by laser processing, and to accurately manufacture a ceramic substrate having excellent insulating properties. ..

The present invention is a method for manufacturing a ceramic substrate in which a circuit layer is formed on the surface, and the present invention is a break line in which a break line is linearly formed along the surface of a ceramic plate having a size capable of forming a plurality of the ceramic substrates. It has a forming step and a dividing step of dividing the ceramic plate on which the break line is formed into individual ceramic substrates, and the break line forming step forms a break line in the air. After forming the break line by irradiating the surface of the ceramic plate linearly with the laser light for processing, the integrated energy density on the ceramic plate is higher than that of the laser light for processing on the surface of the break line. The surface of the break line is oxidized by irradiating it with a small oxidative laser beam.

As described above, when a break line is formed by laser processing, metal is deposited on the surface of the break line to form a modified layer. After that, the modified layer is irradiated with laser light for oxidation having a small integrated energy density. Will oxidize the metal in the modified layer. Therefore, even if the plating treatment is performed after that, the plating does not adhere to the surface of the break line.
It has excellent dimensional accuracy because it does not require etching of the modified layer.

In the method for manufacturing a ceramic substrate of the present invention, the ceramic plate is made of aluminum nitride, the processing laser and the oxidation laser are YAG lasers, and the oxidation laser light has an integrated energy density on the ceramic plate. It is preferably 5 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less.

When the ceramic plate is made of aluminum nitride and the processing laser and the oxidation laser are YAG lasers, the integrated energy density of the oxidation laser light on the ceramic plate is 5 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J. When it is / cm ² or less, it is possible to reliably oxidize the surface of the break line without processing the break line.

In the method for manufacturing a ceramic substrate of the present invention, the ceramic plate is made of aluminum nitride, the processing laser and the oxidation laser are CO ₂ lasers, and the oxidation laser light is the integrated energy density on the ceramic plate. Is preferably 230 J / cm ² or more and 380 J / cm ² or less.

When the ceramic plate is made of aluminum nitride and the processing laser and the oxidation laser are CO ₂ lasers, the integrated energy density of the oxidation laser light on the ceramic plate is 230 J / cm ² or more and 380 J / cm ² or less. , It is possible to reliably oxidize the surface of the break line without processing the break line.

In the method for manufacturing a ceramic substrate of the present invention, the ceramic plate is made of silicon nitride, the processing laser and the oxidation laser are CO ₂ lasers, and the oxidation laser light is the integrated energy density on the ceramic plate. Is preferably 250 J / cm ² or more and 425 J / cm ² or less.

When the ceramic plate is made of silicon nitride and the processing laser and the oxidation laser are CO ₂ lasers, the integrated energy density of the oxidation laser light on the ceramic plate is 250 J / cm ² or more and 425 J / cm ² or less. , It is possible to reliably oxidize the surface of the break line without processing the break line.

In addition to the method for manufacturing a ceramic substrate of the present invention, a circuit layer joining step of joining a circuit layer in a laminated state for each region partitioned by the break line is provided on one surface of the ceramic plate before the dividing step. This makes it possible to manufacture a circuit board.

Alternatively, in addition to the method for manufacturing a ceramic substrate of the present invention, a circuit board is manufactured by having a circuit layer joining step of joining the circuit layers in a laminated state on one surface of the ceramic substrate after the dividing step. You may.

According to the present invention, a break line without a modified layer can be formed on a ceramic plate by laser processing, and a ceramic substrate having excellent insulating properties can be manufactured with high accuracy.

It is a schematic diagram which shows the example of the break line forming apparatus used in the manufacturing method of the ceramic substrate of this invention. It is a schematic diagram of the main part which shows the other example of the break line forming apparatus. It is a schematic diagram which shows still another example of a break line forming apparatus. It is sectional drawing which shows the example of the substrate for a power module manufactured by applying the method of this invention. It is a front view which shows the example which formed the break line in the ceramic plate for manufacturing the substrate for a power module.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 4 shows a power module substrate as an example of a circuit board manufactured by using a ceramic substrate in which a break line is formed on a ceramic plate and individualized as described later.
The power module substrate 10 includes a ceramic substrate 11 which is an insulating substrate, a circuit layer 12 bonded to one surface of the ceramic substrate 11 (upper surface in FIG. 4), and the other surface of the ceramic substrate 11 (FIG. 4). It is provided with a heat radiating layer 13 joined to the lower surface).

As the ceramic substrate 11, for example, a nitride system such as AlN (aluminum nitride) or Si _{3N 4 (} silicon nitride) can be used. In this embodiment, aluminum nitride is used.
The circuit layer 12 is made of aluminum or an aluminum alloy, or copper or a copper alloy, and is bonded to one surface of the ceramic substrate 11 by brazing or the like, and a conductive plating film 14 such as nickel is formed on the surface thereof. There is.
Further, the heat radiating layer 13 is not necessarily limited, but an aluminum material made of aluminum or an aluminum alloy or a copper material made of copper or a copper alloy is bonded to the other surface of the ceramic substrate 11 by brazing or the like.
Then, the semiconductor element 15 is bonded to the upper surface of the circuit layer 12 of the power module substrate 10 configured in this way by soldering, whereby the power module 20 is manufactured. A heat radiating plate, a cooler, or the like is provided on the surface of the heat radiating layer 13 for use.

In order to manufacture the power module substrate 10, first, a flat plate-shaped ceramic plate 30 having a size capable of forming a plurality of power module substrates 10 is irradiated with laser light, and as shown in FIG. 5, vertically and horizontally. A break line 31 is formed in the (break line forming step). Next, the circuit layer 12 and the heat dissipation layer 13 (not shown in FIG. 5) are joined in a laminated state (circuit layer / heat dissipation layer joining step) in the region partitioned by the break line 31 as shown by the alternate long and short dash line. .. Then, after the conductive plating film 14 is formed on the circuit layer 12 (conductive plating film forming step), the ceramic plate 30 is divided from the break line 31 (division step) to be individualized as the power module substrate 10. do.
The dimensions are not particularly limited, but for example, the thickness of the ceramic plate 30 is 0.2 mm or more and 2.0 mm or less, and the depth dimension of the break line is such that the thickness of the portion remaining by the break line is 0. It is from 0.05 mm to 1.8 mm. As the ceramic substrate 11, the plane size is individualized to a size of about 30 mm square.

Next, a method of forming the break line 31 on the ceramic plate 30 in this manufacturing process will be described in detail.
FIG. 1 shows an outline of a device 40 for forming the break line 31.
The break line forming device 40 has a laser light irradiation device 41 and an XY stage 42 that holds the ceramic plate 30 and moves it in the X direction and the Y direction along the surface direction thereof.

The laser light irradiation device 41 includes, for example, a laser oscillator 43 that pulse-oscillates the laser light L by a Q switch using a YAG laser, and a second harmonic (wavelength: 1064 nm) of the fundamental wave (wavelength: 1064 nm) of the oscillated YAG laser. A wavelength converter 44 that converts to (wavelength: 532 nm) to generate laser light L1 and L2 containing these two different wavelengths, and laser light L1 and L2 that have passed through the wavelength converter 44 are laser light L1 having two wavelengths. , L2 separators (harmonic separators) 45 and 46, and condensing lenses 47 and 48 that condense the separated laser beams L1 and L2 in a spot shape.
Then, while moving the ceramic plate 30 held on the XY stage 42 in the X and Y directions, the laser light irradiation device 41 irradiates the two laser beams L1 and L2 to form a break line 31 on the ceramic plate 30.

Specifically, of the two laser beams L1 and L2 separated by the separators 45 and 46, the ceramic plate is processed by the laser beam L2 generated by the second harmonic with a short wavelength to form a linear break line 31 vertically and horizontally. Then, the break line 31 is irradiated with the laser beam L1 by the fundamental wave from behind the traveling direction of the laser beam L2. By passing through the wavelength converter 44, a large number of second harmonics are generated between the second harmonic and the fundamental wave at a ratio of, for example, 6: 4, and the laser beam L1 of the fundamental wave has a small energy. Further, by adjusting the focal position of the laser beam L1 due to the fundamental wave, the surface of the break line 31 is heated, but it is prevented from being deeply processed.

As a result, the modified layer containing the metal component deposited on the surface of the break line 31 due to the processing of the laser beam L2 of the harmonic traveling earlier is heated by the laser beam L1 of the fundamental wave irradiated later, and is oxidized. It becomes a metal oxide (aluminum oxide). In the following description, of the laser beams L1 and L2 separated into two, the laser beam L2 due to the second harmonic with a short wavelength is referred to as a processing laser beam, and the laser beam L1 due to the fundamental wave is referred to as an oxidation laser beam.

In the case of the present embodiment in which the ceramic plate 30 is made of aluminum nitride and the YAG laser is used for the processing laser L2 and the oxidation laser L1, the integrated energy densities of the laser beams L1 and L2 are the processing lasers on the surface of the ceramic plate 30. The integrated energy density of the light L2 is 1 × 10 ⁸ J / cm ² or more, whereas the integrated energy density of the oxidation laser light L1 is smaller than that, 1 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less, preferably 5 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less.
Assuming that the integrated energy density is laser average output: 20 W and pulse repetition frequency is 50 kHz, the average energy (pulse energy) per pulse is 20 W / 50 kHz (J), and the laser average output is P (W). Assuming that the repetition frequency of the pulse is R (kHz) and the focusing diameter of the laser beam is L cm, the energy density (fluence) F per unit area for one pulse is F = (P / R) / (πL ² ). / 4) How much laser pulse energy was applied to the same location, that is, the energy input due to the overlap of the laser pulses focused on the same location is the laser pulse, assuming that the processing speed is Scm / sec. Since the distance traveled between them is S / R (cm), the overlap of pulses at the same location is L / (S / R), and therefore the input energy X (J / cm ² ) to the same location is X. It can be calculated by = F × L / (S / R) = (20 / 50k) / (πL ^2/4 ) × L / (S / 50k).

The integrated energy density is a value on the surface when the ceramic plate 30 is a flat surface. That is, the processing laser light L2 has an integrated energy density of 1 × ¹⁰⁸ J / cm ² or more on the surface of the ceramic plate 30, and the oxidation laser light L1 also has no break line 31 formed. The integrated energy density on the surface of the ceramic plate 30 is 1 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less. Actually, when irradiating the oxidation laser light L1, the break line 31 is irradiated with the laser light L1 after the break line 31 is formed by the processing laser light L2, so that the groove of the break line 31 is irradiated. The integrated energy density on the surface is smaller than that described above. With an integrated energy density of 1 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less, when the ceramic plate 30 on which the break line 31 is not formed is irradiated, the ceramic plate 30 is slightly processed. The integrated energy density is such that
The formation of this break line is performed in air (oxidizing atmosphere).
Further, it is preferable to perform a honing treatment in order to remove the scattered matter generated at the time of forming the break line. The honing treatment can be performed using alumina abrasive grains and water. By performing the honing process, the circuit layer and the heat dissipation layer can be reliably joined to the ceramic substrate in the circuit layer / heat dissipation layer joining step.

In this way, after the break line 31 is formed on the ceramic plate 30 by the processing laser light L2, the processing laser light L2 is irradiated by irradiating the break line 31 with the oxidation laser light L1 at the above-mentioned integrated energy density. The metal of the modified layer formed on the surface of the break line 31 can be oxidized by the irradiation of. Therefore, when the circuit layer 12 is electrolessly plated after the circuit layer 12 and the heat radiation layer 13 are joined, the plating does not adhere to the modified layer.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
In the embodiment, a YAG laser is used, but a carbon dioxide laser (CO ₂ laser), a semiconductor laser, a fiber laser, or the like can also be used.
Further, a CO ₂ laser may be used as the processing laser and a YAG laser may be used as the oxidation laser. Even in this case, the energy density of the oxidation laser is preferably within the above range.
Further, the fundamental wave is the laser beam L1 for oxidation and the second harmonic thereof is the laser beam L2 for processing. However, if the integrated energy density on the surface of the ceramic plate 30 can be set as described above, the fundamental wave and the second harmonic wave are used. It is not limited to the combination of.
Further, the processing laser light L2 and the oxidation laser light L1 were separated by the separators 45 and 46, and the condenser lenses 47 and 48 were used for each of them. As shown in FIG. 2, the processing laser light L2 was used. And the oxidation laser beam L1 may be split by one beam splitter 51 and focused by one condenser lens 52 at a position slightly shifted in the traveling direction. Reference numeral 53 is a reflector.

Further, as in the laser light irradiation device 55 shown in FIG. 3, two laser oscillators 56 and 57 may be used to irradiate the respective laser light L1 and L2.
As a method of reducing the integrated energy density of the oxidation laser light with respect to the processing laser light, the same laser is used for the surface of the ceramic plate, and the same processing position is traced again after processing to determine the focal position of the laser light. There are cases such as shifting, using a laser beam having a large wavelength such as a fundamental wave of harmonics, and the like.
In addition, by inputting an oxidation laser with a large wavelength and a processing laser with a small wavelength into the same optical system, a laser with a large wavelength has a larger focusing diameter than a laser with a small wavelength, and the integrated energy density can be reduced. Is. However, in this case, since the energy of the oxidation laser light is absorbed by the plasma generated by the processing laser, the integrated energy density of the oxidation laser light tends to decrease significantly, so that the pulse of the processing laser is not irradiated. It is preferable to suppress the generation of plasma by irradiating the pulse of the oxidation laser at the timing or by lengthening the pulse interval of the processing laser.

In addition, as a method for manufacturing a substrate for a power module, a break line forming process, a circuit layer / heat dissipation layer joining process, a conductive plating film forming process, and a dividing process were performed in this order. Instead of joining, it may be divided from the break line and separated into individual ceramic substrates (division step), and a circuit layer or the like may be bonded to each ceramic substrate to form a conductive plating film. Further, the heat dissipation layer is not always essential, and it is sufficient that the circuit layer has a step of joining the circuit layers in a laminated state (circuit layer joining step).
Therefore, the method for manufacturing a ceramic substrate of the present invention may include a break line forming step and a dividing step, and a case of manufacturing a ceramic substrate having a circuit layer and a case of manufacturing a ceramic substrate having no circuit layer. It shall include both cases.

In the above embodiment, aluminum nitride is used as the ceramic plate and a YAG laser is used as the processing laser and the oxidation laser. However, the integrated energy density varies in a suitable range depending on the material of the ceramic plate and the type of laser. do.
For example, when a CO ₂ laser is used as a processing laser and an oxidation laser on a ceramic plate made of aluminum nitride, the integrated energy density of the processing laser is 480 J / cm ² or more, whereas the oxidation laser The integrated energy density is preferably 230 J / cm ² or more and 380 J / cm ² or less, and more preferably 280 J / cm ² or more and 340 J / cm ² or less.
Further, for example, when a CO ₂ laser is used as a processing laser and an oxidation laser on a ceramic plate made of silicon nitride, the integrated energy density of the processing laser is 660 J / cm ² or more, whereas it is for oxidation. The integrated energy density of the laser is preferably 250 J / cm ² or more and 425 J / cm ² or less, and more preferably 310 J / cm ² or more and 375 J / cm ² or less.
When a CO ₂ laser is used as the oxidation laser, if the integrated energy density of the oxidation laser is within the above range, the type of processing laser may be a YAG laser, a semiconductor laser, a fiber laser, or a harmonic laser thereof. The effect of can be obtained.

In order to confirm the effect of the present invention, a test was conducted using a break line forming apparatus shown in FIG. 1 using a YAG laser.
A fundamental wave: 1064 nm was used as the laser light for processing, and a second harmonic wave: 532 nm was used as the laser light for oxidation. Then, the surface of the ceramic plate made of aluminum nitride is irradiated with a laser beam for processing at an integrated energy density of 1 × 10 ⁸ J / cm ² to form a break line, and then the break line on which the modified layer is formed is oxidized. The break line is irradiated while changing the integrated energy density of the laser beam for use as shown in Table 1, and then honing treatment is performed using alumina abrasive grains and water, and electroless nickel plating is applied to the surface of the ceramic plate. , It was confirmed whether or not the plating adhered to the break line. "×" for those with plating on the entire surface of the break line, "△" for those with plating at a position deeper than half the depth of the break line, and those with no plating on the break line. It was marked as "○".
The results are shown in Table 1. Sample 5 having an integrated energy density of “0” is an example in which the break line is not irradiated with the laser beam for oxidation.

As is clear from Table 1, in Sample No. 1-4, which was irradiated with an oxidation laser beam having the same integrated energy density as the machining laser beam after forming a break line with the machining laser beam, adhesion of plating was confirmed. rice field.
On the other hand, after forming a break line with the processing laser light, the break line on which the modified layer is formed is irradiated with the oxidation laser light with an energy density lower than that of the processing laser light, whereby the subsequent plating is adhered. It turns out that it can be prevented. If the integrated energy density of the oxidation laser is 1 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less, an insulating portion in which plating does not adhere to the break line surface is formed along the break line. Therefore, it is practical, and it was found that it is better to use 5 × 10 ⁶ J / cm ² or more and 5 × 10 ⁷ J / cm ² or less.

Aluminum nitride is used as the ceramic plate, a CO ₂ laser is used as the processing laser and the oxidation laser, the wavelength is 10.6 μm as the processing laser, the wavelength is 10.6 μm as the oxidation laser, and the integrated energy of the processing laser light is used. The test was carried out in the same manner as in Example 1 while changing the integrated energy density of the laser beam for oxidation as shown in Table 2, except that the density was set to 480 (J / cm ² ).
The results are shown in Table 2.

As is clear from Table 2, in Sample No. 2-1 which was irradiated with an oxidation laser beam having the same integrated energy density as the machining laser beam after forming a break line with the machining laser beam, adhesion of plating was confirmed. rice field.
On the other hand, after forming a break line with the processing laser light, the break line on which the modified layer is formed is irradiated with the oxidation laser light with an energy density lower than that of the processing laser light, whereby the subsequent plating is adhered. It turns out that it can be prevented. Further, if the integrated energy density of the oxidation laser is 230 J / cm ² or more and 380 J / cm ² or less, an insulating portion to which plating does not adhere to the break line surface is formed along the break line, which is practical. It was found that it is better to use 280 J / cm ² or more and 340 J / cm ² or less.

Silicon nitride is used as the ceramic plate, a CO ₂ laser is used as the processing laser and the oxidation laser, the wavelength is 10.6 μm as the processing laser, the wavelength is 10.6 μm as the oxidation laser, and the integrated energy of the processing laser light is used. The test was carried out in the same manner as in Example 1 while changing the integrated energy density of the laser beam for oxidation as shown in Table 3, except that the density was set to 660 (J / cm ² ).
The results are shown in Table 3.

As is clear from Table 3, in Sample No. 3-1 which was irradiated with the oxidation laser beam having the same integrated energy density as the machining laser beam after forming the break line with the machining laser beam, the adhesion of plating was confirmed. rice field.
On the other hand, after forming a break line with the processing laser light, the break line on which the modified layer is formed is irradiated with the oxidation laser light with an energy density lower than that of the processing laser light, thereby preventing the subsequent plating from adhering. It turns out that it can be prevented. Further, if the integrated energy density of the oxidation laser is 250 J / cm ² or more and 425 J / cm ² or less, an insulating portion to which plating does not adhere to the break line surface is formed along the break line, which is practical. It was found that it is better to use 310 J / cm ² or more and 375 J / cm ² or less.

10 Power module substrate 11 Ceramic substrate 12 Circuit layer 13 Heat dissipation layer 14 Conductive plating film 15 Semiconductor element 20 Power module 30 Ceramic plate 31 Breakline 40 Breakline forming device 41, 55 Laser light irradiation device 42 XY stages 43, 56, 57 Laser oscillator 44 Wavelength converter 45,46 Separator 47, 48, 52 Condensing lens 51 Beam splitter L1 Deoxidation laser light L2 Processing laser light

Claims (5)

A method for manufacturing a ceramic substrate in which a circuit layer is formed on the surface.
A break line forming step of forming a break line linearly along the surface of a ceramic plate having a size capable of forming a plurality of the ceramic substrates, and the ceramic plate on which the break line is formed are divided by the break line. It has a division process for individual ceramic substrates,
In the break line forming step, a break line is formed in the air, and after the break line is formed by irradiating the processing laser beam linearly along the surface of the ceramic plate, the surface of the break line is formed. A method for manufacturing a ceramic substrate, which comprises irradiating the ceramic plate with an oxidation laser beam having a smaller integrated energy density than the processing laser beam to oxidize the surface of the break line. The ceramic plate is made of aluminum nitride, the processing laser and the oxidation laser are YAG lasers, and the oxidation laser light has an integrated energy density of 1 × 10 ⁶ J / cm ² or more on the ceramic plate 5 The method for manufacturing a ceramic substrate according to claim 1, wherein the value is ¹⁰⁷ J / cm ² or less. The ceramic plate is made of aluminum nitride, the processing laser and the oxidation laser are CO ₂ lasers, and the oxidation laser light has an integrated energy density of 230 J / cm ² or more and 380 J / cm ² on the ceramic plate. The method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic substrate is as follows. The ceramic plate is made of silicon nitride, the processing laser and the oxidation laser are CO ₂ lasers, and the oxidation laser light has an integrated energy density of 250 J / cm ² or more and 425 J / cm ² on the ceramic plate. The method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic substrate is as follows. In addition to the method for manufacturing a ceramic substrate according to any one of claims 1 to 4, a circuit layer is provided on one surface of the ceramic plate before the dividing step for each region partitioned by the break line. A method for manufacturing a circuit board, which comprises a circuit layer joining step of joining in a laminated state.

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