JP4312031B2 - Metal base circuit board and semiconductor device manufacturing method using the same - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor device used in electrical equipment, a communication device, an automobile, and the like. In particular, the semiconductor device includes a lead frame in which a semiconductor element is mounted on a metal base circuit board, and the semiconductor element. The present invention relates to a metal base circuit board having a specific structure for use in a semiconductor device having a sealed resin mounted thereon.

Semiconductor devices equipped with semiconductor elements are known in a wide range of fields such as electrical equipment, communication equipment, automobiles, etc., especially those using semiconductor elements that flow a large current, such as semiconductor elements and circuits in the semiconductor devices It is also known that metal-based circuit boards are used to dissipate the heat generated from the.

Then, in order to transfer heat to the metal base circuit board while absorbing and buffering transient heat of the semiconductor element, a lead frame is soldered on the circuit of the metal base circuit board, and further a semiconductor element is soldered on the lead frame. It is also known to mount (see Patent Document 1).
JP 2002-314004.

In the structure described above, electronic components such as semiconductor elements are pre-loaded on the lead frame or mounted in a later process. In addition, since the lead frame is used as a part of the terminal that connects to the outside, when the lead frame is soldered on the circuit of the metal base circuit board, the mutual position is maintained as prescribed. Is very important.

However, in the conventional known technology, a paste-like solder cream is printed on a circuit of a metal base circuit board, a lead frame is placed thereon, and the position is fixed by temporarily fixing with the self-adhesive force of the solder cream, Since the solder was melt-bonded in the heating furnace, the lead frame was easily displaced from a predetermined position on the circuit of the metal base circuit board, and it was difficult to mount electronic components in the later process. There are problems such as causing connection failure with other devices.

Therefore, regarding the bonding position alignment between the metal plate of the metal base circuit board and the lead frame, the surface of the metal plate or the surface of the metal base circuit board or by punching in advance from the back surface of the metal base circuit board to a half depth of the metal plate with a press die. A method has been studied in which a protrusion is formed on the back surface and a lead frame alignment hole is fitted to the protrusion. However, providing the protrusions on the front or back surface of the metal plate has problems such as reducing the effective area of the metal base circuit board or causing a physical hindrance when printing and applying the solder paste.

The present invention has been made in view of the above circumstances, and its purpose is to be able to easily and accurately place a lead frame on a metal base circuit board at a predetermined position when soldering. In addition, there is no misalignment in the melting and solidification process in the heating furnace, and highly reliable joining is possible. As a result, the manufacture of a semiconductor element capable of efficiently mounting a highly reliable semiconductor device. It is to provide a method and to provide a metal-based circuit board therefor.

That is, according to the present invention, a semiconductor device is manufactured by mounting a lead frame on which a semiconductor element is mounted and having a fitting terminal portion and a resin sealing the semiconductor element on a metal base circuit board. A step for fitting with the lead frame is provided at a peripheral portion of the main surface opposite to the lead frame mounting side of the metal base circuit board, and the depth of the fitting step is A semiconductor using a metal base circuit board formed 0.01 to 0.5 mm deeper than the lead frame thickness and having a width of the fitting step 0.05 to 0.1 mm larger than the width of the lead frame. It is a manufacturing method of an apparatus.

Since the metal base circuit board of the present invention has a feature in which a fitting step with a lead frame is provided on the peripheral portion of the main surface on the side where the circuit of the metal plate constituting the metal plate is not provided, When mounting the lead frame on the metal base circuit board, it has the feature that it fits with a part of the lead frame and is integrated without variation in dimensions, and it can be integrated with high productivity. Also have.

Since the semiconductor device manufacturing method of the present invention uses the metal base circuit board having the specific structure, a semiconductor device assembled with high productivity and high accuracy can be easily obtained. There is a feature that a reliable semiconductor device can be provided.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a metal base circuit board according to the present invention and a method for manufacturing a semiconductor device using the same.

FIG. 1A is a diagram showing an example of a metal base circuit board according to the present invention, a plan view of a surface of a metal plate 1 where a circuit 3 is not provided, and a cross section of a portion indicated by AA ′ therein FIG. A fitting step 4 for determining the position when the lead frame is mounted is provided on the peripheral portion of the main surface of the metal plate 1 where the circuit 3 is not provided. The fitting step has a shape in which the metal base circuit board has one set each of a long side portion and a short side portion, and the fitting step is provided at least on the long side portion facing the metal plate. In particular, the effect of the present invention can be easily achieved, which is particularly preferable. The circuit 3 is electrically insulated from the metal plate 1 by an insulating layer 2 made of a resin containing an inorganic filler.

FIG. 1B is a cross-sectional view when the lead frame 6 is placed after the solder paste 5 is applied to the circuit 3 and a plan view when viewed from the side where the circuit is not mounted. A terminal portion 7 for fitting with a metal plate prepared in advance on a part of the lead frame 6 is combined with the fitting step 4 provided on the peripheral portion of the main surface on the side where the circuit of the metal plate 1 is not provided. The lead frame and the metal base circuit board are aligned.

In the case of FIG. 1B, after melting solder in a heating furnace and connecting the two, an electronic component or the like is further resin-sealed to obtain a resin-sealed semiconductor device. Since the semiconductor device uses the metal base circuit board having the characteristics described above, when the solder is melted in a heating furnace and both are connected, the dimensional accuracy is remarkably improved as compared with the conventionally known technology. A reliable semiconductor device can be obtained.

The metal base circuit board used in the present invention may be any one as long as it is provided with a step difference with the lead frame, and its production method is also a conventionally known method. I do not care. For example, an insulating adhesive made of a curable resin containing an inorganic filler is applied to a main surface opposite to the one main surface of a metal plate provided with a step at a peripheral portion of one main surface in advance, and the resin is A method is known in which a metal foil is laminated on the insulating adhesive before being sufficiently cured, the resin is sufficiently cured, and then the metal foil is processed by etching or the like to form a circuit.

In the present invention, with respect to the depth of the fitting step provided on the metal plate, it was expected that there was no particular technical reason to determine this, but according to the results of the study by the present inventors, the thickness of the lead frame And is preferably selected from 0.35 to 2.1 mm.

The inventor considers the reason as follows. That is, the thickness of the lead frame is generally 0.3 to 1.5 mm, and it is important that the lead frame does not protrude from the back surface of the metal plate when fitted into the fitting step. Since a semiconductor device using a metal base circuit board of the present invention is generally a resin-encapsulated semiconductor device, heat generated from a sealed electronic component attached to a heat radiating fin is transmitted through a lead frame, an insulating layer, and a metal plate. It is necessary to efficiently radiate heat to the radiating fins. For this purpose, the back surface of the metal plate and the radiating fins need to be in close contact with each other. Therefore, it is important that the depth of the fitting step is set slightly deeper than the thickness of the lead frame. It is preferable that the depth is 0.01 to 0.5 mm deeper than that, and the numerical range is preferably selected.

Further, in the metal base circuit board of the present invention, the width of the fitting step is important in preventing the positional deviation from the conductive circuit and obtaining high positional accuracy when the lead frame is mounted. When the lead frame is placed on the solder paste and the solder is melted in a heating furnace, the lead frame may be displaced due to vibration or horizontal inclination. Therefore, the difference between the width of the fitting step and the width of the lead frame is preferably as small as possible. However, when mounting, the greater the difference between the two, the better the workability. Therefore, the width of the lead frame and the fitting step is selected in view of the balance between the two. In general, the width of the fitting step may be 0.05 to 0.1 mm larger than the width of the lead frame. Also, the width of the terminal portion for fitting between the fitting step of the lead frame and the metal plate to be joined needs to have an appropriate strength, and if it is too large, the effective space in the lead frame will be insufficient. Therefore, usually 1 mm to 5 mm is preferably selected.

In the metal base circuit board of the present invention, the means for forming the fitting step need not be particularly concerned as described above, but a method by press molding or end mill cutting is adopted. Press molding is a press mold equipped with a punch corresponding to the fitting step, and the fitting step on the back side of the metal plate is pressed from the back side to a predetermined depth with a press to make the fitting step easy and efficient. It can be obtained with uniform accuracy, and it requires initial investment for a press die, but it is suitable for mass production processing with a large quantity. In the end mill cutting method, the back surface of the metal plate can be easily obtained by rotating the end mill, and a press die is not required.

In the present invention, the metal plate 1 may be aluminum, iron, copper or the like, or any of these alloys and composite materials, but has good heat dissipation, is inexpensive and lightweight, and has a fitting step due to press molding. Easy to form. The plate thickness is usually 1.0 to 5.0 mm.

In the present invention, the insulating layer 2 has insulating properties, and any thermosetting resin can be adopted. Examples of these resins include epoxy resins, phenol resins, unsaturated polyester resins, polyimide resins, and the like. These resins are mentioned. Among these, the epoxy resin is preferably selected because it is excellent in adhesiveness with the metal plate 1 and the conductive circuit 3. In addition to using the resin alone, the resin can be used in the form of glass cloth, powder or fiber filled with various inorganic fillers, or a combination thereof. It should be noted that additives such as pigments, lubricants and the like can be appropriately added to the resin as long as the objects and effects of the present invention are not impaired.

As the inorganic filler, those having high electrical insulation properties and high thermal conductivity such as aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, boron nitride and the like are preferable. With respect to these inorganic fillers, when an epoxy resin is selected for the insulating layer, the insulating layer can be highly filled. Aluminum oxide and aluminum nitride are preferably selected because the layer can be obtained inexpensively.

Further, the circuit 3 may be formed by attaching a copper foil and forming a pattern by etching, and further applying Ni plating or Au plating.

As the lead frame 4 used when manufacturing the semiconductor device of the present invention, any of 42Ni-Fe alloy, copper plate, copper plate with Ni plating or Au plating, copper alloy, etc. can be adopted. Usually 0.5 to 2 mm is used. In addition to the soldering part on which a normal electronic component is mounted, it is necessary to have a structure having a fitting terminal part 7 below.

As the sealing resin for the semiconductor device, any insulating material can be used. For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a polyimide resin, or the like is used. In addition to using the resin alone, the resin can be used in a form filled with various inorganic fillers in the form of powder or fiber, or a combination thereof. As the inorganic filler, those having high electrical insulation and high thermal conductivity such as aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, boron nitride and silica are preferable.

[Example] On an aluminum plate (5052H34) having a thickness of 3.0 mm, a resin composition composed of an epoxy resin containing aluminum oxide powder was applied so that the thickness after heat curing was 120 μm. After curing so as to be in a B stage state in a heating furnace, a metal base substrate on which a 35 μm thick copper foil serving as a circuit was pasted was created.

A conductive circuit is formed on the metal base substrate by etching, and a press step is used to form a fitting step on the peripheral portion of the main surface where the metal plate circuit is not provided, and then punched for lead frame mounting. A metal base circuit board was prepared.

Here, the width of the fitting step was 1.6 mm, the depth was 0.95 mm, and the depth was 1.0 mm. The width and depth of the fitting step were adjusted by the punch size and mounting position of the press die. The depth can be arbitrarily set at the position of the descent point of the press machine, and can appropriately correspond to a change in the thickness of the lead frame. The punch material of the press mold may be harder than the metal plate, and may have wear resistance and toughness. In this embodiment, SKD11 was adopted.

Next, a solder paste is applied on the circuit of the metal base circuit board to a thickness of 0.2 mm, and a lead frame fitting portion having a thickness of 0.7 mm and a width of 1.5 mm is formed on the fitting step of the metal base circuit board. The metal base circuit board was sandwiched between the lead frame main body part and the terminal part while the upper part was placed on the solder paste on the circuit. Subsequently, it heated with the heating furnace, the solder paste was melted, and the metal base circuit board and the lead frame were joined.

About the semiconductor device before resin sealing obtained by the above operation, the positional accuracy between the lead frame and the conductive circuit was measured. The measurement accuracy was measured by measuring the difference between the two positions of the 10 semiconductor devices from the design position with the side length machine Nikon VM-1000N, and measuring the average value, the minimum value, and the maximum value. The results are shown in Table 1.

[Comparative Example] A metal base insulating substrate having the same configuration as the example and having no fitting step was prepared, and the lead frame was soldered. And the same evaluation as an Example was performed and the result was shown in Table 1.

Since the metal base circuit board of the present invention has a step for fitting and fixing the lead frame to the back surface of the metal plate, a highly reliable semiconductor device can be easily obtained with high reproducibility. It is advantageous for manufacturing a semiconductor device because it has an advantage that it can be mounted efficiently without causing a positional shift between the circuit and the lead frame that could not be achieved by the conventional method.

Since the semiconductor device manufacturing method of the present invention uses the metal base circuit board having the specific structure, the lead frame can be mounted efficiently with high positional accuracy by simply inserting a part of the lead frame into the fitting step and soldering. As a result, the surface area of the substrate can be used effectively, the heat generated by the electronic components can be efficiently dissipated, the density of the mounted components can be increased, and a lightweight, small and highly reliable semiconductor device can be obtained. It can be applied to a wide range of industries such as electrical equipment, communication equipment, and automobiles.

(A) The figure which shows an example of the metal base circuit board based on this invention. (B) The figure which shows the state which mounted the lead frame on the metal base circuit board based on this invention.

Explanation of symbols

1: Metal plate 2: Insulating layer 3: Circuit 4: Fitting step 5: Solder paste 6: Lead frame 7: Terminal part

Claims (1)

A method of manufacturing a semiconductor device by mounting a lead frame on which a semiconductor element is mounted and having a fitting terminal portion on a metal base circuit board and a resin sealing the semiconductor element, A step for fitting with the lead frame is provided at the peripheral portion of the main surface opposite to the lead frame mounting side of the metal base circuit board, and the depth of the fitting step is less than the thickness of the lead frame. A method of manufacturing a semiconductor device, comprising using a metal base circuit board having a depth of 01 to 0.5 mm and a width of the fitting step being 0.05 to 0.1 mm larger than a width of the lead frame.

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