JPH03108362A - Circuit board for mounting semiconductor, and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for coating a conductor circuit with a resin, excluding at least the part on which the components are mounted, to prevent a drop in withstand voltage. The present invention relates to a circuit board for mounting a semiconductor tower which has excellent heat dissipation when a power semiconductor device such as a triac is mounted thereon, and a method for manufacturing the same.

(Prior art) Conventionally, circuit boards have been made of ceramics such as aluminum plates, copper plates, iron plates, and stainless steel plates with ceramic layers such as alumina, aluminum nitride, beryllia, and silicone carbide. A metal base substrate provided with a resin insulating layer containing a resin or an inorganic filler is used. As shown in FIG. 4, when bubbles 12 were attached to the conductor circuit 4, this circuit board was made by applying solder resist to the conductor circuit parts other than the semiconductor device, resistor, and lead terminal parts to prevent solder adhesion when making the circuit board. There is also a method of applying solder resist 13 between the conductor circuits 4 to prevent the inflow of solder, as shown in FIG. Because a portion of the conductor circuit 4 is exposed, electric field concentration occurs, and the insulating layer around the conductor circuit 4 is gradually destroyed, causing insulation failure and a decrease in withstand voltage. In addition, in the case of a hollow package as shown in Figure 5, a discharge phenomenon occurs within the hollow space, and the plasma generated at this time oxidizes the surface of the insulating layer, and as this phenomenon is repeated, the insulating layer becomes thinner. This may cause insulation failure and a drop in withstand voltage.

(Problems to be Solved by the Invention) The present invention solves these drawbacks by covering the conductor circuit of the circuit board with a resin-like material except for the parts mounting part to remove air bubbles, and to prevent air bubbles from forming during use. By completely relaxing the electric field concentration,
It was discovered that it was possible to prevent a decrease in withstand voltage and also to prevent a decrease in heat dissipation by minimizing the thickness of the insulating layer, and a circuit board for mounting semiconductors and a method for manufacturing the same were completed.

(Means for Solving the Problems) That is, the present invention is characterized in that an insulating substrate provided with a conductor circuit is coated with a resin or an inorganic filler-containing resin insulator T-coating on at least the peripheral portion of the conductor circuit, A circuit board for mounting a semiconductor device, and a method for manufacturing the same, characterized in that a semiconductor device or the like is mounted on the exposed portion of the conductor circuit.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention, in which an insulating layer or a ceramic plate 3 is laminated on a heat sink 2, and a conductor circuit 4 is provided. A semiconductor device 5, a resistor 6, etc. are mounted on the conductor circuit 4, and at least an edge portion of the conductor circuit 4 is covered with an insulator 11. Furthermore, in FIG. 2, the radiation fin 1 is joined to the radiation plate 2,
The semiconductor device 5 and the like represent an example of an embodiment of the present invention in which the semiconductor device 5 and the like are sealed with a resin sealing material 9. Further, the semiconductor device described above may be sealed with a hollow package 8 as shown in FIG.

The material of the heat sink 2 used in the present invention is copper, iron, nickel, aluminum, brass, stainless steel, or the like. The insulating layer or ceramic plate 3 may be made of epoxy resin, polyimide resin, an insulating layer made of these resins filled with an inorganic filler, or reinforced with fibers such as glass fiber, or ceramics such as alumina, silicone carbide, aluminum nitride, beryllia, etc. board is used.

The conductor circuit 4 used in the present invention includes copper, iron, nickel,
It may be a metal foil such as brass, an association thereof, or a laminate of different metals. In particular, in the case of copper foil, it may be plated with gold or nickel in advance to facilitate wire bonding.

Next, the insulator 11 used in the present invention is preferably one that has good adhesion to the conductor circuit 4 in order to remove air bubbles 12 attached to the conductor circuit 4, and is made of, for example, epoxy resin, polyester resin, or these resins. It may contain a different resin capable of polycondensation, an inorganic filler with excellent thermal conductivity such as silica, fused silica, alumina, and a different heat-resistant resin powder.

The insulator 11 is applied to the conductor circuit 4 with a thickness of 3 μm to i, oo.
It is preferable to cover with a thickness of 0 μm. If the thickness is less than 6 μm, all the air bubbles cannot be sufficiently removed and a decrease in withstand voltage cannot be prevented. Furthermore, the coating thickness u i, o
Although there is no problem even if the thickness exceeds fc, IU is not effective in preventing a drop in withstand voltage, and the preferred thickness is i, ooo μm from the standpoint of processing such as coating.

Next, the insulator 11 can be used by covering the entire surface of the conductor circuit 4 and peeling off the part on which the semiconductor device 5 etc. will be mounted, but the position where the semiconductor device 5 etc. will be mounted must be determined in advance. For example, it is also possible to expose the location t- beforehand.

Alternatively, after the semiconductor device 5 and the like are mounted on the conductor circuit 4, the remaining 9 portions may be covered with the insulator 11. As shown in FIG. 3, it is effective to cover the insulator 11 continuously from the surface layer of the conductor circuit 4 to the side and bottom reeds to prevent a drop in withstand voltage.
) is 50 circles or more in width, which is effective in preventing a drop in withstand voltage.

Also, from the side to the bottom, the width of (1)) is 100 μm.
A thickness of preferably 500 μm or more is effective in preventing a drop in withstand voltage. As a method of coating the conductor circuit 4 with the insulator 11, screen printing and spraying are preferred, and any other coating method may be used as long as it does not damage the entire circuit board. A specific method for manufacturing a circuit board is to form a conductor circuit made of the metal foil on a heat sink to which the insulating layer or ceramic plate is welded via an adhesive. Next, remove the entire surface of the conductor circuit surface layer or the periphery of the surface layer, excluding the areas where semiconductor devices (transistors, diodes, etc.), resistors (chip resistors, chip capacitors, etc.), terminals, etc. of the conductor circuit are planned to be mounted. The insulating material is applied continuously from the part to the side surface, the insulating layer, or the surface of the ceramic plate by, for example, screen printing or spraying. After the insulator is cured, a component such as a semiconductor device is mounted on the exposed portion of the conductor circuit. Then, the conductor circuit surface is sealed with a resin sealant or a hollow package, and if necessary, a heat dissipation fin is attached to the bottom of the heat dissipation plate.

The circuit board for mounting on a conductor tower of the present invention is for a power semiconductor device tower mounting module in a broad sense, and also includes a circuit board for hybrid integration ([C)].

Furthermore, when applying resin or resin insulating material containing an inorganic filler to the periphery of a conductor circuit, it is desirable to cover the entire periphery of the conductor circuit, but depending on the size of the semiconductor device, resistor, lead terminal, and board. Although a portion of the periphery of the conductor circuit may be exposed, the degree of reduction in withstand voltage is small and does not significantly affect the effect. Furthermore, the insulator 11 used in the present invention may cover all other conductive circuits 4 instead of being in close contact with mounted components such as the semiconductor device 5 as shown in FIGS. 1 and 2.

As described above, the present invention eliminates air bubbles by forming a resin-like insulation in at least the peripheral portion of a conductor circuit, and also eliminates the difference in relative permittivity of each constituent material, that is, the relative permittivity of the insulating layer of a ceramic substrate or a metal base substrate. is usually 7.0 to 4.
0 degrees Celsius, but the resin used to seal it usually has a dielectric constant of 5.0, and the dielectric constant of the resin or inorganic filler-containing resin insulator applied to the peripheral portion of the conductor circuit is usually 4.0 to 4.0 degrees. The dielectric constants of these three types are different, which leads to relaxation of electric field concentration and prevents a decrease in withstand voltage.

(Example) Example 1 A conductor circuit was formed by bonding copper foil with a thickness of 1 (175 μm) to a 100 μm thick alumina substrate using silver paste. 1 towards the center
．． An extremely low viscosity liquid epoxy resin was continuously sprayed to a thickness of 5 μm over the width of No. 11, the side surface, and the two widths of the alumina surface. After heating and curing the epoxy resin, parts such as a semiconductor device were mounted on the exposed portion of the conductor circuit, and an outer case was adhered thereto, followed by injection of an epoxy resin containing S10□ for sealing.

Next, a voltage of AC4, Q kv/at room temperature was applied between the conductive circuit and the heat sink to reduce the lifespan. The average dielectric breakdown life was 146 hours. For comparison, we measured all the conductor circuits without resin coating, and found that the average lifespan was 47 hours.

Example 2 A composite foil of an 85 μm thick copper foil and a 40 μm thick aluminum foil was bonded to a 6B thick aluminum substrate having an 80 μm thick insulating layer as an inorganic filler and highly filled epoxy resin adhesive. The entire conductor circuit was formed by etching. Next, a 200 μm width from the surface layer R portion of the conductor circuit of the conductor circuit surface semiconductor device, etc. toward the center, the side surfaces, and the insulating layer 3H width were screen printed with a SiO□-containing epoxy/melamine resin t-15 μm thick. .

Next, after the resin coated portion was cured, a semiconductor device, a resistor, a terminal, etc. were mounted thereon, and then an outer case was adhered, and an epoxy resin containing 810□ was injected with gold and sealed. The completed circuit board is 1
When a lifespan test was conducted in an open room at 25°C with an AC single wave of 800V peak, the average lifespan was 27 hours. For comparison, measurements were taken of a conductor circuit without resin coating, and the average lifespan was 8 hours.

Example 3 Example 20 Same as Example 2 except that hollow pack-22 was used instead of SiO□-containing epoxy resin injection sealing for the circuit board.
As a result of performing the same operation as above, the average lifespan was 15 hours,
In addition, when no solder resist was applied, the time was 4 hours.

(Effects of the Invention) As described above, the present invention provides a circuit board in which the entire periphery of the conductor circuit is coated with a resin-like insulator to completely prevent the adhesion of air bubbles, and the circuit board is assembled with different dielectric constants. By using this, the electric field concentration is completely relaxed, the withstand voltage is prevented from decreasing, and the life of the circuit board is extended.

[Brief explanation of drawings]

FIG. 1 shows a side sectional view of the circuit board of the present invention, and FIG. 2 shows a side sectional view of the circuit board of the present invention sealed with a resin sealing material. FIG. 5 is an enlarged side cross-sectional view of the circuit board of the present invention. FIG. 4 is a side sectional view of a conventional circuit board, and FIG. 5 is a partial side sectional view showing a state in which air bubbles are attached to a conductor circuit. Figure 6 shows the conductor circuit part completely exposed.
A plan view of a conventional example in which other parts are covered with solder resist. Code 1...Radiation fin 1...Terminal 2...
・Heat sink 8...Package 3・
...Insulating layer or ceramic plate 9...Resin sealing material 4
...Conductor circuit 10...Wire 5
... Semiconductor device #t 11 ... Insulator 6
...Resistor 12...Bubble 13.
・Solder resist

Claims (3)

[Claims] 1. 1. A circuit board for mounting a semiconductor, comprising an insulating substrate provided with a conductor circuit, and at least a peripheral portion of the conductor circuit is coated with a resin or an inorganic filler-containing resin insulator. 2. A semiconductor comprising an insulating substrate provided with a conductor circuit, at least a peripheral portion of the conductor circuit being coated with a resin or an inorganic filler-containing resin insulator, and a semiconductor device or the like being mounted on the exposed portion of the conductor circuit. Tower-mounted circuit board. 3. A conductor circuit is formed on an insulating substrate, at least a peripheral portion of the conductor circuit is coated with a resin or an inorganic filler-containing resin insulator, and then a semiconductor device is mounted on the exposed portion of the conductor circuit. A method for manufacturing a circuit board for mounting a semiconductor tower.