JPS5810860B2 - Electronic device manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electronic devices such as semiconductor devices and integrated circuit devices, and particularly to assembly techniques thereof, and can be effectively utilized in the production of power electronic devices.

In general, power electronic devices differ from small signal electronic devices in that they require large heat dissipation flanges.
The assembly between flanges and lead wires is complicated, and the mold mold used for sealing with resin or the like is also complicated, which has delayed the industrialization of electronic devices for small signals.

Therefore, the present application attempts to provide several new techniques that are effective in industrializing power electronic devices.

Below, these techniques will be described in detail with reference to specific examples.

Thereby, the specific purpose, characteristics, and effects of the invention of the present application will be understood.

FIG. 1 shows a top view of a fringe for attaching an electronic element, and FIG. 2 shows a longitudinal cross-sectional view of the fringe, which is made by punching out a plate-shaped body with a press.

Industrially, flanges for, for example, 10 electronic devices are manufactured in a series of integrated shapes.

In the figure, 1 indicates a flange main body having a thickness of 126 mm, a width of 8 mm, and a length of 30 mm per unit, and the heat generated in the elements connected to the flange is effectively dissipated to the outside. Copper, aluminum, or an alloy mainly composed of these materials, which have good properties, or a clad plate made of the above-mentioned materials as the main plate are used.

It is effective to form a nickel plating layer on the surface of the flange depending on the purpose of corrosion protection, and this will be explained in detail later.

The notch 2 formed in the flange 1 is a mold material flow prevention notch formed to prevent the molten mold material from flowing out to unnecessary portions in the mold sealing process to be performed later.

The holes 3 are bolt holes through which the external heat sink and the flange are brought into close contact when the electronic device is completed, thereby making it possible to significantly increase heat dissipation.

Reference numeral 4 designates an open slit tab insertion portion formed for inserting a tab of a lead frame which will be explained later.

The narrow protrusion 5 forming the outer circumference of the tab insertion part 4 is a tab holding part formed to swage the tab located inside the tab insertion part 4, and in the figure, it is swaged with a small pressure. Although the tab insertion part is separated at the upper center part as shown in FIG. In that case, the tab insertion portion 4 has a closed slit shape.

Further, the tab insertion portion 4 is formed to be long in the same direction as the length direction of the 7 langes (left and right directions in the figure), but this is because when pressing the tab by caulking the protrusion 5, It is effective for the work if force is applied from the direction, and the reason why the tab insertion parts 4 are formed as a pair in the vertical direction in the figure is that the pressure from caulking prevents errors in the positional relationship between the lead frame and the flange 1. This is to effectively utilize the elasticity of the lead frame during caulking and caulking.If these purposes are not taken into consideration, the length direction of the tab insertion part should not be set in a direction perpendicular to the length direction of the flange. The number of tab insertion portions may be changed, or the number of tab insertion portions may be one.

The groove portion 1 is a groove of about 4 or 5 φ formed to define a position 8 where an element is to be deposited.

The seven flange bodies described above can be manufactured by a single press process, and it is desirable that at least the groove 7 be constructed integrally with the press die for forming the tab insertion portion 4.

That is, the element attachment position 8 and the tab insertion part 4 are defined in a fixed positional relationship, and therefore the positional relationship between the lead frame held by the tab insertion part 4 and the element attachment position 8 is accurately defined.

Figure 3 shows the flange body 1 shown in Figures 1 and 2 above.
2 is a vertical cross-sectional view showing a state in which a nickel film 9 of, for example, 5 μm is formed on the surface of the device by, for example, plating, and a silver foil 10 of, for example, 500 μm is connected to the nickel film 9 at the element mounting position 8 by electric welding.

Particularly when the above-mentioned element is a semiconductor element such as a transistor or a semiconductor integrated circuit element, it is not desirable to attach the element directly to the surface of a flange made of copper or aluminum. There is no effect on the element, heat dissipation is extremely good, and since silver is a soft metal, the size of 4.5 mm x
Even if a fairly large element of about 4.5 mm is attached, the element will not be damaged due to thermal strain, so it is extremely useful as the inclusion 10 between the element and the flange.

Further, the intervening nickel coating 9 of about 1 μ to 10 μ acts as a corrosion-proofing coating for the flange, and also acts as a resistance material in the electric welding between the 7 flange 1 and the inclusion 10, so that the inclusion 10 and the flange body are Make strong connections between people.

In addition to nickel, chromium, molybdenum, tungsten, alloys thereof, and alloys of these with other metals can be used as the resistive material.

In addition, 11 and 12 in the same figure show a part of the electrode for electric welding.

As mentioned above, there is an inclusion 1 such as silver foil between the element and the flange 1.
0, it is an effective method to first connect the inclusion 10 and the flange 1 by electric welding,
It can also be used in many other cases.

That is, if resistance welding is performed so that only the contact surface of the flange 1 or the nickel coating on its surface and the inclusion 10 is melted, the surface of the inclusion, that is, the flat surface on which the element is to be attached, can be maintained as it is, which will be done later. This is because the element can be attached uniformly over the entire surface, and since electric welding is based on heat generation at the extreme part, deterioration of the parts other than the welded part can be suppressed.

In addition, an effective method is to connect the silver foil 10 to the pot flange 1 element mounting position 8 by cold pressure welding. According to this method, the silver and the flange etc. do not change in quality and the surface is flattened over the entire surface. Since the welding is pressed, the flatness is not impaired, so it has the same advantages as the resistance welding described above.

In this case, the nickel film 9 is preferably formed by plating after cold pressure welding, with the silver foil protected by a corrosion-resistant material such as resin.

An effective way to connect the silver foil 10 and the copper flange 1 is to use eutectic at the interface between silver and copper to connect them at a relatively low level. There are two methods, such as a method of connecting through the flange 1 and a method of connecting by melting the entire inclusion, but in these cases, it is necessary to heat the connection at a humidity higher than the element mounting humidity that will be performed later, and it is sufficient to prevent deterioration of the flange 1 and the inclusion 10. Consideration should be given to

FIG. 4 shows a vertical cross-sectional view of the element 13 mounted on the silver foil 10 by soldering, and the element 13 is S
A semiconductor integrated circuit element for power amplification with a size of 2.5 mm x 2.0 mm based on i is used, and its main surface is bonded to the flat silver foil 10 at about 440° C. by a gold-silicon eutectic brazing material 14. uniformly soldered to the flat surface of the

In addition, as an alternative to the above-mentioned soldering connection, a conductive adhesive containing conductive powder such as gold and silver can be used.In this case, it does not require heating and is easy to work with, but it has poor thermal resistance and mechanical strength. Excellent soldering.

Although not shown on the main surface of the device, SiO
an effective insulating film such as 2°Si3N4, and a wiring path extending from an electronic element such as a transistor, diode, or resistor formed inside the semiconductor through the hole and onto the insulating film;
Electrode terminals located at the periphery of the element are formed to connect wires later.

The connection of the silver foil and the element to the flange does not necessarily have to be carried out in the above process, and may be carried out, for example, after the lead frame is connected to the flange.

FIG. 5 is a top view showing the lead frame 20, which is made of, for example, phosphor bronze with a thickness of 0.25 m with appropriate elasticity.
Each electronic device is made of a strip-shaped metal plate with a length of 30 mm, which is photo-processed and then etched using a corrosion-resistant mask formed by the photo-etching technology and press molding technology. can be made.

Alternatively, it can be made using press stamping and press molding techniques.

In any case, as in the case of the flange, if, for example, 10 electronic devices are to be manufactured in series, it is necessary to manufacture such a lead frame in which 10 pieces are connected in series. When using this technology, the above-mentioned series of frames can be made at the same time in one process, and press molding can also be done in one process, but with press punching and press forming technology,
Since the press mold is complicated, we use multiple press molds to
It is preferable to punch out the frames continuously using a set of press dies, rather than processing them simultaneously in multiple presses, to create a series of frames.

21a in the figure is a sealing body (double-dashed line 1 in the figure) which will be explained later.
The lead portion (internal lead portion) located in the portion surrounded by 5 is shown, and its tip is preferably formed so that the above-mentioned element numbering substantially coincides with the outer periphery of position 8.

Reference numeral 21b indicates a lead portion (external lead portion) led out to the outside of the sealing body, and although the shape as a lead is shown in the same figure, it is not necessarily necessary to have such a shape, and it may be made into a half-plate shape. It may also be formed into a lead shape by punching.

The lead parts 21a and 21b constitute an integrated lead wire 21 in the finished product.

Between the many external lead parts 21b, there is a lead frame 2.
The lead holding portion 22a constitutes a part of the lead holding portion 22a.

22b (generally referred to as 22), and the position of the lead holding part 22 is at least the outer lead part 2.
1b may be formed anywhere or all of it, but for the purpose of mechanically holding the internal lead 21a, it is desirable to form at least a portion of it as close to the boundary line 15 of the sealing portion.

This is especially important when sealing by transfer molding (injection molding) of resin or the like is used because it also serves the purpose of stopping the flow of the sealing material.

In addition, in this example in which the external lead portion 21b is shaped as a lead wire, the widths of the two lead holding portions 22a and 22b are different from each other so that the front and back sides of the lead frame 20 can be clearly seen at a glance, and the IJ is wide. The end 22b is for forming a part of a molding material injection pipe (runner).

In addition, in this example, the tip of the lead portion 21b is tapered to facilitate insertion into a printed circuit board, etc., so that the lead portion 21b is easily subjected to unnecessary mechanical action from the outside world. 20 so as to surround the external lead portion 21b, thereby preventing unnecessary deformation of the lead portion 21b during each step until the device is completed and during transportation between the steps.

The hole 23 formed in the lead frame 20 is a guide hole used as a positioning guide during later assembly, cutting of the lead holder, and molding.

The hole 24 is a tab forming hole formed to form a tab 25, and this tab 25 is a tab 25a for connecting to the flange 1. In particular, it is important to maintain a constant positional relationship between the tab 25a and the internal board portion 21a in order to align the element mounting position of the flange 1. As shown in FIG.
A is formed at the same time as in the photo-etching process to define the positional relationship thereof, and then the portion 25 to be made into a tab is bent by press molding.

Further, the inner lead portion 21a and the tab 25 may be formed simultaneously or sequentially by press punching and press molding techniques.

Such a lead frame is plated with silver to a thickness of, for example, 1μ or more for the purpose of increasing the solderability of the lead wires, improving the wire bonding connection between the element lead frames described later, and preventing corrosion. .

Such silver plating treatment may be performed immediately after etching when photoetching is used or after press molding, and may be performed either before or after pressing when all is performed by press.

Further, although gold is a material for achieving the above object, it is expensive, and silver is preferable from an industrial standpoint.

In any of the above methods, the tab 25 is
If a is bent, one end 20 of the tab 25a
This means that the distance W in the length direction on the plane of the lead frame 20 between the center 27 of the internal lead portion 21a group (coinciding with the center of the element mounting position 8) does not change at all before and after bending the tab 25a. This is important because it allows extremely accurate positional relationships to be maintained.

In principle, the basic purpose of the tab 25a can be achieved if there is only one tab 25a for a series of lead frames.

1 and 8 are an enlarged perspective view of the tab forming portion of the lead frame 20 and a vertical sectional view taken along line B-B thereof, with respect to one base line 29 perpendicular to the main surface 28 of the lead frame 20. It has a pair of tabs 25a that are symmetrical to each other to prevent positional deviation in the direction perpendicular to the length direction of the lead frame 20.

In this case, if there is one pair of tabs 25a for a series of lead frames, the basic purpose can be achieved in principle.

Further, the angle 30 formed between the tab 25 and the main surface portion 28 of the lead frame 20 that is connected thereto is slightly larger than 90°.
The angle is sufficiently smaller than 80°, and due to this and the elasticity of the lead frame 20, the connection with the flange 1 can be made strong.

Further, the tip of the tab 25a is bent further outward, but this is to further strengthen the connection with the 7 flange 1, and also the pair of tab insertion holes 4 in the flange 1 at the tip of the tab 25a. If the lead frame 20 is positioned approximately at the center of each of the flange 1,
The connection becomes extremely easy.

As for the material when elasticity is utilized as described above, phosphor bronze Kovar, iron-nickel alloy, nickel, etc. can be used.

Further, the tab 25b does not necessarily have to be formed in the same part as the tab 25a, but it is more effective to form the same part in order to simplify the press molding die. Lead part 21a
It is effective to form the tabs on both sides of the tabs 25a integrally with the tabs 25a in order to reinforce the tabs 25a so that they do not reach there.

Furthermore, as a method for controlling the distance between the lead frame 20 and the flange, a jig is placed on the flange to make it flat and in close contact with the flange, and the tip of the tab 25a is in contact with the surface of the jig. There is a way to do it.

Tab 2 of lead frame 20 obtained as described above
5a is the tab insertion part 4 of the flange 1 to which the element 13 is attached.
Insert into.

At this time, the tabs 25b are in contact with the upper surface of the flange and define a constant interval between the flange lead frames.

On the other hand, the width 31 of the tab 25a at the same height as the tip of the tab 25b of the lead frame should be approximately the same as the length 16 of the tab insertion part 4. The width of the tip of the tab 25a should be set within the allowable value between the tab 25a and the position 8, and the width of the tip of the tab 25a should be made sufficiently smaller than that to allow smooth insertion into the tab insertion portion 4.

Lead frame 2 made with consideration as mentioned above
When using 0 and 7 lunges, the above internal lead part 21
The positional relationship between the tab 25a and the element mounting portion 8 is uniquely determined only by the insertion of the tab 25a.

After being aligned as described above, pressure is applied in the direction shown by the arrow 6 in FIG. 1 to deform the tab holding portion 5 and fix the tab within the slit 4.

At this time, as shown in the cross-sectional view of FIG. 9, the tab 25a comes into contact with the upper and lower parts of the slit due to the pressure in the direction of the arrow 6, and since the lead frame has a certain degree of elasticity, the tab 25a comes into contact with the upper and lower parts of the slit. The contact will be extremely strong.

FIG. 10 is a top view of the main part showing the state in which the tab 25a described above is caulked in the slit 4. Here, it is important to pay attention to only the central part of the tab 25a, that is, the tip of the tab holding part 5 in this example. After sealing, the flange is cut only at the center of the slit 4, where the slit 4 is crimped. Pressure can be reduced and one piece that can be cut can be made larger.

FIG. 11 shows an example of electrically connecting the electrode terminal located on the surface of the element 13 and the internal lead portion 21a by wire bonding.

In the drawing, reference numeral 32 denotes a connector wire made of gold, aluminum, or the like and having a diameter of about 50 μΦ, and its material can be selected depending on the material of the tip surface of the electrode terminal and the internal lead portion 21a, and the connection technique.

For example, if the electrode terminal is aluminum, the internal lead terminal 21a
If the tip surface material is silver and the connection technique is thermocompression bonding, gold is suitable, and if ultrasonic welding is used, aluminum is suitable.

In wire bonding as described above, it is necessary to apply some pressure to connect the internal lead part 21a and the connector wire 32, so that the internal lead part 21a is bent.

On the other hand, in the case of thermocompression bonding, it is necessary to heat the tip of the internal lead portion 21a and the element electrode to about 350°C, and it is also desirable to heat the core part to about 100°C in ultrasonic welding.

For this purpose, as shown in FIGS. 11a and 11b, a metal spacer 33 having good thermal conductivity such as iron or copper may be inserted from a direction perpendicular to the length direction of the flange and removed after bonding.

At this time, if the metal spacer 33 is heated, the internal lead portion 21a can be directly heated.

Furthermore, in Fig. 12, an insulating spacer such as a ceramic ring is positioned and interposed with a silver foil 10 before connecting the flange 1 and the lead frame, and is left in place even after completion. .

In either case, the above heating is performed on the flange mounting table 3.
Since it is easy to use 4 as a heating element, the above spacer 33
It is preferable to use a metal with good heat conductivity or an insulator with good heat conduction such as alumina ceramics or beryllia equipment.

In particular, if the spacer is left attached after completion as described above, it is extremely effective during resin molding, which will be described later. Since it is fixed, it will not move due to the flow of resin during resin injection.

Therefore, problems of internal leads touching each other or wires breaking can be prevented.

Furthermore, according to Ike's example, the connector wire 32 is connected to the electrode terminal using the capillary 35, and then, as shown in FIG. This is carried out by bringing the core into contact with the flange 1 or silver foil, heating the core, connecting the connector wire, and then using the elasticity of the internal lead part 21a to return it to its original position as shown in Figure 13. can do.

In this case, if the connection to the element 13 is made first, there is a problem that the connector wire 32 is pulled upward when the internal lead portion 21b returns to its original position, as shown in FIG. 32, and connect the connector wires as shown in FIG. 13a.

Alternatively, the connector wire 32 may first be connected to the internal lead portion 21a, and after the internal lead 21a has returned to its original position, the connector wire may be connected to the electrode terminal of the element 13.

As is clear from the above explanation, by providing a spacer as shown in FIG. 12 between the lead tip and the flange, (1) the lead does not wobble during wire connection.

■Since the lead is in contact with the flange via a spacer, it is easy to heat the lead tip.

Effects such as this can be obtained. Next, the assembly completed as described above is placed in a mold, and as shown in FIGS. 14a and 14b, a resin injection pipeline (runner ) 36, inject an encapsulant such as resin, and after solidifying the resin, remove the mold jig, and if the tips of the lead holding part 22 and external lead part 21b are in contact with the lead frame 20, also cut the core part. However, if the flange 1 is cut into each device as described above, a structure as shown in the coffin 15 will be obtained, and if this is further folded appropriately, the lead portion will be inserted into the hole of the printed circuit board as shown in FIG. 16. 21
The structure can be easily inserted.

[Brief explanation of the drawing]

Fig. 1 is a top view showing the 7 flange, Fig. 2 is a vertical cross-sectional view taken along the line A-A in Fig. 1, and Fig. 3 shows the state in which a nickel coating is formed on the flange in Fig. 2 and a silver foil is connected. 4 is a vertical sectional view showing the state in which an electronic element is connected to the flange shown in FIG. 3, FIG. 5 is a top view showing the lead frame, and FIG. 6 is a step in manufacturing the lead frame. Enlarged view showing a part of the lead frame in No. 7
8 and 8 are respectively a perspective view and a vertical sectional view taken along the line B-B showing a part of the lead frame, and FIGS. 9 and 10 are a sectional view and a sectional view showing the state of connection between the lead frame and the flange, respectively. The top view, FIG. 11a is a plan view showing the state of electrical connection between the lead frame and the element, and FIGS. 14a and 14b are a top view and a side sectional view showing the position of the resin injection pipeline, respectively.
FIG. 5 is a perspective view showing an example of a completed electronic device.
FIG. 16 is a perspective view showing an example of a completed electronic device pond. 1 is the flange body, 2 is the notch for preventing mold material flow, 3 is the bolt through hole, 4 is the tab insertion part, 5 is the tab holding part, 6 is the direction of pressure applied to the tab holding part, 7 is the element mounting Groove indicating position, 8 is element mounting position, 9 is nickel coating, 10 is silver foil, 11 is electric welding electrode, 12
13 is an electric welding electrode, 13 is an electronic element, 14 is a gold-silicon eutectic brazing material, 15 is a boundary line of a sealing body, 16 is a length of a tab insertion part, 20 is a lead frame, 21 is a lead wire, 2
1a is an internal lead part, 21b is an external lead part, 22 is a lead holding part, 22a is a narrow lead holding part, 22b is a wide lead holding part, 23 is a guide hole, 24 is a notch hole for forming a tab, 25 is a tab, 26 is the tab side edge, 21 is the center of the internal lead group, 28 is the life surface of the lead frame, 29 is a baseline perpendicular to the life surface of the lead frame, 3
0 is the angle formed by the lead frame and the tab, 31 is the tab 25
The width of a, 32 is the connector wire, 33 is the spacer, 34
35 is a flange mounting table, 35 is a capillary, 36 is a resin injection pipeline, and 37 is a sealing material such as resin.

Claims (1)

[Claims] 1. To mount an electronic device, place a lead on the 7-lunge so that it overlaps it at a predetermined distance, and attach a spacer between the tip of this lead and the flange, and attach a spacer to a part of the tip of the lead. A method for manufacturing an electronic device, which comprises connecting connector wires and then resin molding with the spacer attached.