JP4846455B2 - A method for manufacturing a nitride ceramic circuit board. - Google Patents

Description

The present invention relates to a method for manufacturing a nitride ceramic circuit board.

  Ceramic substrates such as alumina, beryllia, silicon nitride, and aluminum nitride are used for circuit boards for semiconductor devices used for power modules and the like from the viewpoint of thermal conductivity, cost, safety, and the like. These ceramic substrates are joined with a metal circuit such as Cu or Al or a heat sink to form a circuit substrate. These are characterized in that high insulating properties can be stably obtained with respect to a metal substrate using a resin substrate or a resin layer as an insulating material. Among these ceramics, aluminum nitride is a particularly suitable material in terms of high thermal conductivity, high insulation, harmlessness, and the like.

Such a circuit board is manufactured through a process of manufacturing a joined body made of a ceramic substrate and a metal plate, but various efforts have been made from the viewpoint of improving productivity. For example, a method in which a required number of ceramic green sheets are connected and fired and then divided (Patent Document 1) or an aluminum nitride substrate having a copper circuit board is used to simultaneously manufacture a plurality of wiring boards by using dividing lines. The method etc. are mentioned (patent document 2).
JP-A-2-233561 JP-A-8-32204

However, in the method shown in Patent Document 1, productivity may be reduced because cracks are generated from the connected portions due to thermal stress applied to the connected portions during firing. There is a problem that the above strength is required and the depth of the dividing line is limited.

An object of the present invention is to provide a method for manufacturing a nitride ceramic circuit board having good insulation and excellent productivity.

  That is, the present invention relates to a method of manufacturing a circuit board by inserting a scribe line with a laser into a nitride ceramic substrate and dividing the substrate, and after inserting a scribe line composed of discontinuous laser holes in the nitride ceramic substrate. , A method of manufacturing a nitride ceramic circuit board that is joined to a metal plate by an active metal method and forms a circuit by an etching method. After forming a circuit by etching, the brazing material remaining in the metal plate removal portion, A method for producing a nitride ceramic circuit board, comprising removing an alloy layer, a nitride layer, etc., and producing a nitride ceramic circuit board having a laser hole interval of 0.2 mm or less (not including 0) This is a method for manufacturing a nitride ceramic circuit board in which the tip angle of the cross section of the laser hole is 30 degrees or more. Furthermore, the laser is a carbon dioxide gas laser of 50 to 500 W at a pulse frequency of 1 kHz or more.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nitride ceramic circuit board which is excellent in insulation and excellent in productivity is provided.

The nitride ceramic substrate is not particularly limited, but it is preferable to use an aluminum nitride substrate or a silicon nitride substrate. Moreover, although the thickness is not specifically limited, the thing of about 0.3-3.0 mm is common.

  The present invention is characterized in that a scribe line composed of discontinuous laser holes is formed. Compared to general oxide ceramics, nitride ceramics are more likely to deposit metal components by thermal decomposition with laser. Therefore, when a scribe line is inserted continuously, the metal precipitates due to heat accumulation lower the insulation. There is also a problem that the depth of the scribe line is not constant. Constituting with discontinuous laser holes alleviates the accumulation of heat, and the deposition of metal components from the nitride ceramic substrate becomes uniform in a small amount, so that productivity and reliability are improved.

The distance between the laser holes is more preferably within 0.2 mm (excluding 0). If the distance exceeds 0.2 mm, it may not be possible to divide along the scribe line, and cracks may occur in the circuit direction from the dividing surface, which may reduce the withstand voltage.
The cross-sectional tip angle of the laser hole is preferably 30 degrees or more. When the tip angle of the cross section of the laser hole is less than 30 degrees, there is a problem that when dividing the scribe line, it becomes difficult to divide or the brazing filler metal remains in the laser hole and electrical insulation cannot be obtained. May occur. The optimum size (diameter) of the laser hole is appropriately determined according to the depth and angle of the laser hole, but is generally 0.04 mm to 0.5 mm.

  In the present invention, after scribing the nitride ceramic substrate, a metal plate to be a circuit is joined and a circuit is formed by an etching method. The metal component deposited from the nitride ceramic substrate at the time of scribing can be removed at the same time as the metal plate at the time of etching, and the reliability can be further improved.

The laser used in the present invention is a carbon dioxide gas laser, a YAG laser, or the like, but a carbon dioxide gas laser is preferable because a processing time is required for the YAG laser in consideration of the absorption wavelength of nitride ceramics. Among them, a carbon dioxide laser of 50 to 500 W at a pulse frequency of 1 kHz or more is preferable because it has an effect on mitigating heat shock.

The depth of the scribe line is preferably ¼ to ３ of the ceramic substrate thickness. If the depth is less than 1/4, it is difficult to separate along the scribe line, and if it is greater than 1/3, it may break when a semiconductor chip or the like is mounted. The dividing groove may be formed only on one surface of the ceramic substrate, or may be formed on both the front and back surfaces.
Moreover, as a processing speed, even if it carries out by normal 1000-5000 mm / min, there is no problem.

  Although the thickness of the metal plate to be joined is not particularly limited, it can be appropriately determined according to the flowing current. In general, a thickness of 0.1 to 0.5 mm is often used. The purity of the metal plate is preferably 90% or more. When the purity is lower than 90%, when the ceramic substrate and the metal plate are joined, the reaction between the metal plate and the brazing material may be insufficient, or the metal plate may become hard and the reliability of the ceramic circuit substrate may be reduced. Depending on the application, a composite metal plate may be used.

In general, either a molten metal method that does not use a bonding material or an active metal brazing method can be used for bonding a nitride ceramic substrate and a metal plate, but the productivity is good and bonding can be performed at a relatively low temperature. An active metal brazing method is preferred.
Metal alloys such as Si, Mg, Cu, Al, Ge, Ag, Ti, Mg, and Zr are suitable as the brazing material. The brazing material is used as a paste or foil. The brazing material may be applied to or placed on either the nitride ceramic substrate or the metal plate. When an alloy foil is used, the metal plate and the alloy foil may be clad in advance.

The coating amount of the brazing material is preferably 5 to ²⁰ mg / cm ^{2 on} a dry basis. If the coating amount is less than 5 mg / cm ² , an unreacted portion may be generated. On the other hand, if it exceeds 20 mg / cm ² , the time for removing the bonding layer may become long and productivity may be lowered. The coating method is not particularly limited, and a known coating method such as a screen printing method or a roll coater method can be employed.

In order to form a circuit pattern on the nitride ceramic circuit board, an etching resist is applied to the metal plate and etched.

There is no restriction | limiting in particular regarding an etching resist, For example, the ultraviolet curing type and thermosetting type generally used can be used. There is no particular limitation on the etching resist coating method, and a known coating method such as a screen printing method can be employed. The etching solution is not particularly limited, and for example, a ferric chloride solution, a cupric chloride solution, sulfuric acid, a hydrogen peroxide solution, etc. can be used. 2 copper solution.

The nitride ceramic circuit board from which unnecessary metal parts have been removed by etching has the applied brazing material, its alloy layer, nitride layer, etc. remaining, inorganic acid such as aqueous solution of ammonium halide, sulfuric acid, nitric acid, peroxide It is common to remove them using a solution containing hydrogen water.

  There is no restriction | limiting in particular regarding the plating resist which concerns on this invention, A solvent dry type ink, UV hardening type ink, etc. can be used. The coating method is not particularly limited, and a known coating method such as a screen printing method or a roll coater method can be employed. It is desirable that the coating thickness is 0.005 to 0.07 mm after drying. If the thickness is less than 0.005 mm, the metal may be partially exposed. On the other hand, if the thickness is more than 0.07 mm, it takes time to remove the plating resist, and the productivity may decrease.

Although there is no restriction | limiting in particular regarding a plating process, From surfaces, such as workability | operativity and cost, electroless nickel plating, electroless nickel gold plating, and solder plating are mentioned as a preferable thing. The thickness of the plating layer is not particularly limited, but is preferably 2 to 8 μm. If the plating thickness is less than 2 μm, it may adversely affect mounting characteristics such as solder wettability and wire bonding characteristics. On the other hand, if the plating thickness exceeds 8 μm, the substrate characteristics may be adversely affected due to peeling of the plating film or the like.

There is no particular limitation on the method for removing the plating resist, and examples thereof include a method of removing using an organic solvent such as ethanol and toluene, and a method of immersion in an alkaline aqueous solution.

The nitride ceramic circuit board thus manufactured is joined to an electronic component such as a base plate or a semiconductor element by solder. The type of solder is not particularly limited, but usually tin, lead, silver, bismuth and the like are generally used. The soldering method is not particularly limited. For example, there is a method in which a solder paste is applied to a predetermined portion by a screen printing method or the like, and a component or the like is mounted and then placed in a furnace at a temperature at which the solder melts. The solder layer is preferably not in contact with the side surface of the metal circuit from the viewpoint of the reliability of the nitride ceramic circuit board.

[Examples 1-6, Comparative Example 1 to 7
On one main surface of the aluminum nitride substrate, division grooves were formed by laser processing under the processing conditions shown in Table 1 so that each set could be separated. Laser processing was performed using a commercially available device (trade name “LMP-221-200” carbon dioxide laser manufactured by Shinwa Tech Co., Ltd.). Thereafter, an active metal brazing paste (metal component: a paste of polyisobutyl methacrylate containing Ti 3% -Zr 2% -Ag 90% -Cu 5%) is applied to both main surfaces of the aluminum nitride substrate (coating amount: 10 mg / cm ² ). Then, a copper plate (dimensions: 61 mm × 51 mm × 0.3 mm: manufactured by Dowa Mining Co., Ltd .; oxygen-free copper plate) was stacked and heated and bonded in a vacuum at 850 ° C. for 1 hour. After that, etching resist (manufactured by Taiyo Ink Manufacturing Co., Ltd .: product name UVR150G) is printed in a predetermined shape (combined shape of L shape and reverse L shape), then etched with aqueous copper chloride solution to form a circuit, and then the substrate The surface was plated with electroless nickel to produce a circuit board. This circuit board was cut along the dividing grooves by bending it by hand, and four circuit boards were manufactured.

  In the process of manufacturing these circuit boards, the presence / absence of metal precipitates, insulation characteristics, and the division failure rate at the time of division were measured as follows (n = 20). The results are shown in Table 1.

<Measuring method>
(1) Presence / absence of metal deposits Presence / absence of metal deposits was confirmed with an optical microscope after laser processing. Precipitates were confirmed by elemental analysis by SEM / EDAX analysis.
(2) Insulation characteristics The insulation resistance between the front and back of the circuit board was measured with an insulation resistance meter ("VMG-1000" manufactured by Ando Electric Co., Ltd.).
(3) Divided defect rate Except for the scribble line subjected to laser processing, the number of divided substrates was examined to obtain the defect rate. It was confirmed with an optical microscope (magnification 100 times) whether it was divided other than the scribe line.
<Materials used>
Aluminum nitride substrate: manufactured by Denki Kagaku Kogyo, trade name “ANP” (dimensions: 60 mm × 50 mm × 0.635 mm, thermal conductivity: 150 W / m · k, bending strength: 350 MPa)
Silicon nitride substrate: manufactured by Denki Kagaku Kogyo, trade name “SNP” (dimensions: 60 mm × 50 mm × 0.635 mm, thermal conductivity: 70 W / m · k, bending strength: 700 MPa)
Aluminum oxide substrate: Kyocera product name “A-476”

An example of a conventional nitride ceramic substrate with laser processing Nitride ceramic circuit board with scribble line showing one embodiment of the present invention Sectional drawing of the nitride ceramic circuit board which shows one Embodiment of this invention

Claims (1)

In a method of manufacturing a circuit board by inserting a scribe line with a laser into a nitride ceramic substrate and manufacturing the circuit board, the nitride ceramic substrate is passed through the center of the hole with a carbon dioxide laser of 50 to 500 W at a pulse frequency of 1 kHz or more. After inserting a scribe line composed of discontinuous laser holes with a cross-sectional tip angle of the laser hole, which is the intersection angle of the tangent lines at both ends in the cross section to be 30 degrees or more, and the interval does not include 0 and is within 0.2 mm Then, it is joined to a metal plate by an active metal brazing method, and a circuit is formed by an etching method. Then, the brazing material, its alloy layer, and nitride layer remaining in the metal plate removal portion are removed, and a method for manufacturing a nitride ceramic circuit board.