JPS5941320B2 - Multilayer circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer circuit board using thermal spraying.

Conventionally, various methods have been implemented to manufacture multilayer circuit boards.

For two-layer circuit boards, an effective method is to form conductor circuits on the front and back sides of an insulating board, then drill holes at the required locations on the board and make the holes conductive by plating or other methods. Since it is limited to two layers and cannot be applied to three or more layers, it is not included in the scope of the multilayer circuit board in the present invention.

As a method for manufacturing a multilayer circuit board having three or more layers, the following two methods are generally implemented.

In the first method, first, a double-sided copper-clad or single-sided copper-clad resin substrate is prepared. In this case, the resin is kept in a semi-cured state, that is, in a B-stage state. Then, the copper on the substrate is etched into a desired pattern to obtain a first layer substrate. Next, a substrate having a second layer pattern is obtained by the same method, and each substrate having a third layer pattern and subsequent layers is further obtained. These substrates are then stacked on top of each other via guide pins and heat pressed to integrate them. Thereafter, holes are drilled at required locations to connect the interlayer conductors, and through-hole conductors are formed in the holes by plating or other methods. The problems with this first method are as follows (1) -
There is something like (4). (1) There is a possibility that the resin becomes fluid during the hot pressing stage, causing the copper foil pattern to collapse, which may cause pattern displacement and pattern breakage. (2) The process is complicated and the yield is reduced. Furthermore, manufacturing costs are also high. (3) Since the insulating layer is made of resin, heat dissipation is poor, and there are restrictions when increasing the density or when mounting components to which power is applied.

(4) Since only the conductor layer can be formed on the inner layer, miniaturization is restricted by the area of the components to be mounted.

On the other hand, the second method uses ceramics,
This is broadly divided into printing methods and green sheet methods.

The printing method repeats two steps: printing a four-conductor paste on a ceramic substrate and firing it, and then printing and firing an insulating paste whose main component is glass except for the areas where the upper and lower conductors are connected. In particular, it is a method for obtaining a multilayer circuit board with a desired number of layers. Problems with this printing method include the following (1) to (4). (1) The process is simple, just repeating the steps of printing, drying, and firing, but since the connection between the upper and lower conductors is also attempted to be achieved by printing the upper layer conductor, it can lead to poor connections and an increase in the number of inspection steps. As a result, manufacturing costs increase.

(2) Since an insulating layer mainly made of glass is used, as the number of layers increases and the insulating layer becomes thicker, the heat dissipation property decreases rapidly, so it is not suitable for high density.

(3) A ceramic board is required as the first substrate, but
Large ceramic plate without warping (10cTrL square or more)
is extremely expensive, making it extremely difficult to obtain a large substrate at a practical price. (4) It is difficult to use a curved substrate. In addition, in the green sheet method, a ceramic green sheet is made, a conductor pattern is formed on the front and back of this sheet with a refractory gold layer paste such as W or MO, and the required upper and lower conductor connections (through holes) are made. This is a method in which a plurality of sheets are stacked and pressed together using a multilayer press, and then the entire sheet is fired in a reducing atmosphere. Similar to this, there is a method in which insulating layers and conductive layers are alternately printed on a green sheet, but this is considered to be equivalent to the green sheet method. Problems with this green sheet method include the following (1) to (4). (1
) The green sheet shrinks by approximately 10% during firing, but even if the pattern is formed in advance with this in mind, there will be an error of about ±1% of the required dimension, so it will be difficult to adjust the dimensions for subsequent printing, component mounting, package, etc. It is necessary to provide a large amount of leeway.

(2) Since refractory metal paste such as W and MO is used,
Firing must be carried out in a reducing atmosphere, leading to an increase in the complexity and scale of manufacturing equipment.

(3) It is difficult to use a curved substrate.

(4) The time required for the manufacturing process is long. in this way,
Conventionally, there are various methods for manufacturing multilayer circuit boards, but each method has the problems described in the above sections and is not satisfactory.

For this reason, the following method (1) is used for manufacturing multilayer circuit boards:
The items shown in ~(7) are requested. (1) It can be implemented through a simple process, and it is not unreasonable in terms of the manufacturing process even if the number of layers of multilayer circuits is calculated. (2) It can be manufactured at a lower cost than conventional multilayer circuit boards. (3) Since multilayering is also a means of achieving higher density, it must have better heat dissipation than conventional substrates.

(4) High reliability of conductor layer interconnection.

(5) Applicable to curved substrates. (6) The materials used are not limited to precious metals or high-purity materials.

(7) The inner layer can accommodate not only a conductor layer but also elements such as resistors, capacitors, thermistors, switches, and thermal elements as necessary.

The present invention has been made in consideration of these circumstances, and its purpose is to provide a method for manufacturing a multilayer circuit board that satisfies the above-mentioned demands.

That is, the present invention includes the steps of printing a thermal sprayed resist made of resin on an insulating layer in a pattern opposite to a desired conductive pattern, then thermally spraying a highly conductive metal material, and then removing the resist to form a conductive layer; A desired insulating pattern and a reverse pattern are placed on the conductor layer. The process of printing a thermal spray resist made of resin on a turn, then thermal spraying an insulating ceramic material, and then removing the resist to form an insulating layer is repeated alternately, and a resin composition is applied to each layer formed by the thermal spraying. The object is to achieve the above object by impregnating and curing the material.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1a-1 is a schematic cross-sectional view showing a manufacturing process of a multilayer circuit board according to an embodiment of the present invention.

First, prepare a metal plate 1 of any size, and
The upper surface is roughened physically or chemically, and then a thermal spray resist 2 made of resin is printed on the upper surface of the metal plate 1 in a pattern opposite to the desired insulation pattern as shown in FIG. 1a. For this printing, screen printing, patterning using photoresist, and various other methods can be applied. Next, an insulating ceramic material 3 having good thermal conductivity such as alumina, magnesia, titania, zirconia or zirconia silicate is sprayed uniformly over the entire surface of the metal substrate 1 as shown in FIG. 1b. At this time, if the maximum diameter of the sprayed ceramic material 3 is selected to be 44 [μm] or less and the spraying conditions are appropriately selected, the sprayed ceramic material 3 can be prevented from adhering to the resist 2. Thereafter, by peeling off the resist 2 using a suitable solvent, a first insulating layer 4 made of a thermally sprayed ceramic material 3 is formed as shown in FIG. 1c. Next, a thermal spray resist 2 is printed on the upper surface of the insulating layer 4 in a pattern opposite to the desired conductor pattern, as shown in FIG. 1d. Subsequently, metal powder (metal material) 5 made of copper, aluminum, tungsten, molybdenum, or an alloy mainly composed of these is sprayed onto the metal plate 1 and the insulating layer 4 as shown in FIG. 1e. At this time, if the maximum diameter of the sprayed metal material 5 is selected to be 44 [μm] or less and the spraying conditions are appropriately selected, the sprayed metal material 5 can be prevented from adhering to the resist 2. Thereafter, by peeling off the resist 2 using a suitable solvent, a first conductor layer 6 made of the sprayed metal material 5 is formed as shown in FIG. 1f. Next, the second insulating layer 7 and conductor layer 8 are formed by repeating the same method as above.

That is, as shown in FIG. 1g, after printing the thermal spray resist 2 in a pattern opposite to the desired insulation pattern, that is, in the areas where the first and second conductor layers 6 and 8 need to be connected,
A ceramic material 3 is thermally sprayed, and then the resist 2 is peeled off as shown in FIG. 6H to form a second insulating layer 7. and,
After printing a desired conductive pattern and conductive pattern ζ≦sprayed resist 2 on the upper surface of the insulating layer 7 as shown in FIG. 1, the metal material 5 is sprayed, and then the resist 2 is peeled off as shown in FIG. Then, the second conductor layer 8 is formed. Subsequently, the same method is repeated to form a third insulating layer 9 and a conductive layer 10, respectively, as shown in FIGS. 1K and 1I. In this way, a three-layer circuit board is formed, but when used as an electric circuit in this state, each layer 4, 6, -, 10 formed by the thermal spraying is porous and minute cracks occur, causing each layer 4 to , 6, -, 10 have continuous holes throughout, so the withstand voltage between the conductor layers 6, 8, 10 and the metal plate 1 is small, and furthermore, when it is humid, insulation failure between the upper and lower conductors may occur, causing circuit damage. It ceases to function as a.

In order to prevent this, a resin composition made of a monomer, a prepolymer, or a combination thereof is made to have a low viscosity and penetrates from the surface layer, that is, the third insulating layer 9, into the inner layer, especially the second and first insulating layers 7 and 4. let At this time, it may be carried out in the atmosphere, but it may also be carried out in a vacuum or in an ultrasonic bath. The monomer and prepolymer are preferably those that polymerize and cure three-dimensionally, are thermally stable and have excellent electrical properties, such as epoxy prepolymer diallyl phthalate, thermosetting polybutadiene, triazine resin, bismaleide resin, Examples include triallyl cyanurate, polymide resin, divinylbenzene, glycidyl methacrylate, polydimethylsiloxane resin, and polyurethane resin. Furthermore, if necessary, the monomer and prepolymer must be prepared in advance with catalyst curing agents, initiators, dyes, pigments, surfactants, silane coupling agents, antioxidants, anti-aging agents, ultraviolet absorbers, and fine particles for rheology adjustment. An inorganic filler (0.1 μm or less) or another resin component may be added as a modification component. After the resin composition containing the monomer or prepolymer as a main component is infiltrated into each of the layers 4, 6, to 10 formed by thermal spraying, it is cured by appropriate means, such as heat curing or electron beam curing. Alternatively, three-dimensional reticulation (curing) is performed by means such as ultraviolet curing.

Next, by physically scraping off the resin composition remaining on the top layer, the outermost conductor layer 10 is exposed, thereby obtaining the intended three-layer circuit board.
By this resin impregnation method, the circuit board becomes electrically reliable, and at the same time secures close contact with each other inside each layer and with the metal plate 1, thereby increasing mechanical strength. Note that the above resin impregnation method does not necessarily require the above-mentioned layers 4, 6,
It is not necessary to do this after ~, 10 are formed.

For example, each time each layer from the first layer to the third layer is formed,
That is, the resin composition may be impregnated and cured for each state shown in FIG. 1 F, j, and I. Furthermore, each layer was impregnated with a resin composition to form up to the third layer. The resin composition may be cured in the state shown in FIG. 1. According to the method of this embodiment described above, the following effects (1) to (8) are achieved.

(1) The process of resist printing on the metal plate 1 - thermal spraying of ceramic material - resist peeling - resist printing - thermal spraying of metal material - resist peeling is repeated and the resin composition is only impregnated and hardened, which is more effective than conventional methods. The work is simple and easy to automate.

(2) In relation to item (1) above, the manufacturing cost is significantly reduced compared to conventional multilayer circuit boards.

(3) The insulating layers 4, 7, 9 are integrated with the metal plate 1,
In addition, since it is made of a ceramic material 3 with good thermal conductivity, a multilayer circuit board with a high heat dissipation structure can be realized, and it can be adapted to high density and high power. (4) Conductor layers 5, 8, 1
0 and metal plate 1, it is possible to prevent breakage due to uneven surfaces as in conventional printing methods, and the reliability of the connection is improved.

(5) It is possible to prevent the temperature of the metal plate 1 from rising during thermal spraying; for example, by performing thermal spraying while cooling the metal plate 1, the temperature of the metal plate 1 can be maintained at room temperature.

Therefore, the relative positional accuracy of the metal plate 1, each pattern of the insulating layers 4, 7, 9, and each pattern of the conductive layers 6, 8, 10 is increased as much as possible, and the subsequent automation of component mounting, bonding, etc. Continuation can be easily performed. (6) Since a metal plate is used as the circuit board, the cost is low and there are no restrictions on its size.

(7) If necessary, thermal spraying can be applied to the necessary locations even after parts are mounted.

(8) It is also possible to easily increase the thickness of only a layer having a conductor layer with a large current capacity, such as an earth pattern or a power supply win pattern.

Next, another embodiment of the present invention will be described with reference to FIG.

Which embodiment is a method of manufacturing a multilayer circuit on a metal plate 11 having a curved surface shape. First, the metal plate 11 is subjected to press working or the like to form a curved surface as shown in FIG. Next, the upper surface of the metal plate 11 is roughened by a sand blasting method or the like. After that, the metal plate 1 is
A desired resist pattern is formed on 1. Here, when the metal plate 11 is grounded and a positive high voltage signal is applied to the resist ink (sprayed resist) 13 housed in the quick jet 12, droplets fly from the tip nozzle 12a toward the metal plate 11. The droplets reach the shortest distance between the nozzle 12a and the metal plate 11 and form a resist film on the metal plate 11. Therefore, by applying an electric signal to the ICJet 12 based on information stored in advance in a computer and scanning the ICJet 12 from side to side and in the front and back directions of the page, a desired resist pattern can be formed on a metal plate with a curved surface. 11. At this time,
It is desirable that the relative distance between the metal plate 11 and the IC jet 12 is always constant, and if the metal plate 11 or the IC jet 12 is moved vertically based on data stored in a computer in advance, the distance will always be constant. A resist can be formed on the metal plate 11 in this manner. After the resist is formed, the ceramic material can be thermally sprayed by scanning the nozzle tip of a thermal spraying machine (not shown) in the left and right, front and back directions of the paper. Also,
It is desirable to keep the distance between the nozzle tip and the metal plate 11 constant as in the case of resist formation. Thus, as in the previous embodiment, the metal plate 11 is formed by repeating the steps of resist coating (resist printing) - ceramic material thermal spraying - resist peeling - resist coating - metal material thermal spraying - resist peeling.
A multilayer circuit will be formed on top.

Therefore, according to this embodiment, not only the same effects as those of the previous embodiments but also the ability to easily form a multilayer circuit board having a curved surface are achieved. Note that the present invention is not limited to the embodiments described above.

For example, an insulating plate may be used instead of the metal plate serving as the bottom layer. In this case, the process of forming the conductor layer on the insulating plate and the process of forming the insulating layer thereafter may be repeated alternately. Furthermore, it goes without saying that the number of circuit layers is not limited to three, and may be more than three. Furthermore, it can be applied to the formation of resistors, capacitors, etc. in addition to conductor layers and insulating layers. For example, when forming a resistor, as shown in FIG. 3, an insulating layer 4 made of a sprayed ceramic material is formed on a metal plate 1, and then conductive layers 21a and 21b made of a sprayed metal material are formed on the insulating layer 4. followed by nickel-chromium alloy, nickel-rulin alloy, tantalum, tungsten, molybdenum, silicon carbide, stannous oxide, germanium,
A composition having a suitable resistivity such as ruthenium oxide, graphite, panadium pentate, titanium oxide, glass, or a cermet type resistive material that combines ceramic and a resistive material is applied to the conductor layers 21a and 21b and both ends thereof. The resistor 22 is formed by thermal spraying in an overlapping manner.
At this time, if resistive materials with different specific resistances are formed using different resists, a range from low resistance to high resistance can be covered in accordance with the aspect ratio of the resistor. Similarly, when forming a capacitor, as shown in FIG. 4, an insulating layer 4 is formed on a metal plate 1, a lower conductive layer 23 is formed, and then strontium titanate, titanium oxide, titanium calcium oxide, lead titanate, barium titanate, or alumina as a low dielectric material,
Dielectric layer 2 is formed by spraying magnesia, forsterite, steatite beryllia, zirconia, zirconia silicate, etc.
4 and then by forming the upper conductor layer 25, a capacitor with a desired capacitance can be formed.
Furthermore, various electric elements, such as switch elements, PTC elements, and thermistor elements, can be formed at arbitrary locations on the multilayer circuit board using similar techniques. Further, the size of the thermal spraying material, thermal spraying conditions, etc. may be determined as appropriate according to specifications.

Furthermore, the material of the resist, the method of forming the resist pattern, etc. may be appropriately determined according to the specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 a-1 is a schematic cross-sectional view showing the manufacturing process of a multilayer circuit board according to one embodiment of the present invention, FIG. 2 is a schematic diagram for explaining another embodiment, and FIGS. 3 and 4 are schematic cross-sectional views for explaining modified examples, respectively. 1, 11... Metal plate, 2... Thermal spray resist, 3... Ceramic material, 4, 7, 9...
... Insulating layer, 5 ... Metal material, 6, 8, 10
・・・・・・Conductor layer.

Claims (1)

[Claims] 1. A conductor layer is formed by printing a thermal spray resist made of resin on the insulating layer in a pattern opposite to the desired conductor pattern, then thermally spraying a highly conductive metal material, and then removing the resist. Step 1 and a second step of printing a thermal spray resist made of resin on the conductor layer in a pattern opposite to the desired insulation pattern, then spraying an insulating ceramic material, and then removing the resist to form an insulation layer. a step of alternately repeating the first and second steps to form a desired number of conductor layers and insulating layers; and a step of impregnating and curing at least one layer formed by the thermal spraying with a resin composition. A method for manufacturing a multilayer circuit board, comprising: 2. The method of manufacturing a multilayer circuit board according to claim 1, characterized in that an insulating substrate is used as the insulating layer in the first step. 3. The multilayer circuit according to claim 1, characterized in that an insulating layer formed on a metal plate by a step similar to the second step is used as the insulating layer in the first step. Substrate manufacturing method. 4. The step of impregnating and curing the resin composition involves repeating the first and second steps alternately to form a desired number of conductor layers and insulating layers, and then impregnating each layer from the top layer with the resin composition. 2. The method of manufacturing a multilayer circuit board according to claim 1, wherein the multilayer circuit board is cured. 5. Claim 1, wherein the step of impregnating and curing the resin composition is a step of impregnating and curing the resin composition for each layer formed in the first and second steps. A method of manufacturing the multilayer circuit board described above. 6. The step of impregnating and curing the resin composition involves impregnating each layer formed in the first and second steps with the resin composition, and curing the impregnated resin composition after all the layers are formed. 2. The method of manufacturing a multilayer circuit board according to claim 1, wherein the method is a method for manufacturing a multilayer circuit board. 7. The method of manufacturing a multilayer circuit board according to claim 1, characterized in that electrically passive elements are housed in desired locations of the conductor layer formed in the first step by a thermal spraying method. 8. The method of manufacturing a multilayer circuit board according to claim 3, wherein the metal plate has a desired curved surface shape.