JP3176566B2 - Cover plate for heat rail - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a heat rail in which a lead frame is conveyed and heated when a semiconductor pellet is assembled into a lead frame. The present invention relates to a cover plate structure that can be maintained as a non-oxidizing atmosphere.

[0002]

2. Description of the Related Art An example of a conventional heat rail will be described. FIG. 3A is a plan view thereof, and FIG. 3B is a side view showing a cross section taken along line AA in FIG. 3A. The heat rail 1 includes a heat block 2 having a U-shaped cross section and a concave opening thereof facing upward. A heater (not shown) is embedded in the heat block 2, and a dish-shaped adapter rail 4 covering almost the entire surface is disposed on the bottom surface of the concave portion 3 with the concave surface facing downward. The heat block 2 is provided with a gas flow path from an inert gas inlet 5 provided on the outer surface toward the bottom of the concave portion. Therefore, a space formed by the adapter rail 4 and the bottom of the concave portion of the heat block 2 serves as a tank 6 for storing the introduced inert gas. A cover plate 7 is attached to the upper surface of the heat block 2 so as to cover the recess 3, and the recess 3 forms a tunnel 3 a.

When assembling a semiconductor pellet (not shown) to a lead frame (not shown), the lead frame (not shown) is heated while being transported on the adapter rail 4 and solder (not shown) or semiconductor Pellets (not shown) are supplied and assembled. At this time, an inert gas such as nitrogen gas is introduced from the inert gas inlet 5 to prevent oxidation of the lead frame and the solder. The introduced inert gas fills the tank 6 and is blown into the tunnel 3a from gas outlets 4a provided around the adapter rail 4, and is discharged from the inlet and outlet of the tunnel 3a as an inert atmosphere.

In order to make the inside of the tunnel a good atmosphere even with a flow rate of the inert gas as small as possible, the tunnel 3a is required.
The opening of the cover plate 7 is also required to be as small as possible because the opening of the
a, a hole 7b for stirring and spreading the melted solder, and a hole 7c for supplying semiconductor pellets. When a lead frame feed mechanism is provided in the tunnel 3a, the cover plate 7 is used.
Only the holes provided above are necessary. However, the tunnel 3a becomes large, the distance from the cover plate 7 to the lead frame becomes large, and it becomes an obstacle to speeding up the supply of semiconductor pellets and the mechanism becomes complicated. Transporting the lead frame from outside is also performed. Figure 3 in that case
As shown in (A), a hole 7d for a conveying claw is provided. The hole 7d for the transfer claw is also made as small as possible, and the transfer claw sends the lead frame by the square motion for each semiconductor device. At a place where the inert gas is discharged including these holes, a flow rate must be provided so that the outside air does not flow back into the tunnel 3a.

[0005]

However, in recent years, the speed of the device has been required to be increased, and the transfer of the lead frame for each semiconductor device has a limit in the speed of transfer, so that a longer range, for example, for one lead frame. Or 1 /
For two lengths, it is under consideration to use step feed with the nails on.

In order to feed such a lead frame with an external claw , the present inventor prototyped a heat rail 11 as shown in FIG. The cover plate 17 is obtained by a pawl slit 17c sends a feed pawl hole 7 d in the cover plate 7 of the heat rail 1 shown in FIG. 3 (A) and extending from the entrance to the tunnel to the exit.

As a result of a test using this heat rail, if the opening area is increased in this way, a good atmosphere in the tunnel cannot be obtained with the same flow rate of the inert gas as in the prior art. Even if the supply of the inert gas was increased, the atmosphere was not as satisfactory as the conventional one. This means that the outside air that enters the tunnel has openings in addition to the work and tools that move it into the tunnel to supply and transport lead frames, solder, semiconductor pellets, etc. Therefore, it is estimated that there is a component flowing backward.

Accordingly, the present invention provides a cover plate for a heat rail with reduced inflow of outside air.

[0009]

In order to solve the above-mentioned problems, the present invention relates to a heat rail cover plate for forming a tunnel for covering a concave portion of a U-shaped cross section of a heat block and conveying a lead frame. In addition, the present invention provides a heat rail cover plate characterized in that the heat rail cover plate has an opening and a member is erected in the form of a screen at the opening end. The screen-like member preferably surrounds the opening in the form of a chimney. However, even if a part of the opening is inevitably cut off for the purpose of the opening, it is effective.
According to the above configuration, when the air is thin like the conventional cover plate, the backflowing outside air at the opening end raises the screen-like member, so that the path becomes long like a chimney and the backflow cannot be performed. Such an operation will be described in detail with reference to the drawings. FIG. 2A shows a conventional thin cover plate 7.
Is a case in which a hole 7a is simply opened. In this case, the inert gas is blown out from the hole 7a as shown by a solid arrow to prevent the inflow of outside air. At the end of the hole 7a, it is not a vortex action or a convection action. It can be estimated that the outside air is taken in. However, FIG. 2 (B)
When the screen-like member 28 is provided at the end of the hole 7a as described above, the outside air that is about to flow backward as indicated by the broken line arrow is taken out by the discharged inert gas (solid line arrow). Further, there is provided a cover plate for a heat rail in which the thickness of the plate is increased to at least 8 mm or more at an opening instead of providing a screen-like member. A similar effect can be obtained by increasing the thickness of the cover plate. Note that the limitation of “8 mm” does not change the effect critically in this respect, and in the conventional design, there are various thicknesses around 3 mm that happen to be designed, so it is different from the thicker ones that exist in the past. Therefore, it should be regarded that the present invention is applied to the case where the thickness exceeds 8 mm.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a plan view thereof, and FIG. 2B is a side view showing a cross section taken along line AA in FIG. 1A. The heat rail 21, the heat block 2, the adapter rail 4, the inert gas inlet 5, and the tank 6 are the same as those of the conventional example shown in FIG. The difference is the cover plate 27.

The cover plate 27 has a solder supply hole 27a and a hole 2 for agitating and spreading the melted solder.
7b, a supply hole 27c for supplying a semiconductor pellet. In addition, a slit 27d for conveying nails is provided instead of the hole 7d for conveying nails. As a feature of the present invention, L-shaped plate members 28 are attached to both sides as screen members along the slit 27d. The thickness of the cover plate 27 body is 3 mm, the width of the slit 27 d is 3 mm, and the height of the screen member 28 is 10 m.
m. No screen members are attached to the other holes 27a to 27c.

With the above configuration, a satisfactory atmosphere in the tunnel was obtained. This is because most of the slit 27d occupying a considerable portion of the entire opening of the cover plate 27 is prevented by the partition member 28 from backflow of the outside air.

In the above embodiment, a 10 mm-high partition member is provided on the cover plate 27 having a thickness of 3 mm. However, the present invention is not limited to this, and the minimum height required according to the flow rate of the inert gas to be supplied is as follows. different. For example, when the height of the partition member is set to 5 mm under the same gas flow rate conditions, the atmosphere in the tunnel is not in a satisfactory state, but the effect is clearly seen as compared with the case without the partition member.

According to the above-described embodiment, the backflow path of the outside air is lengthened by setting the screen member to prevent the outside air from entering, but the same effect can be obtained even if the thickness of the cover plate is increased.

Naturally, it is preferable to arrange the partition member so as to surround the opening in a chimney shape from the viewpoint of securing the atmosphere. However, even if there is a partially missing portion as in the above embodiment, a certain effect can be obtained. is there.

[0016]

As described above, according to the present invention,
Even if a large opening is provided in the cover plate, an inert atmosphere can be secured in the tunnel of the heat rail.

[Brief description of the drawings]

FIG. 1A is a plan view of a heat rail using one embodiment of the present invention. FIG. 1B is a side view showing a cross section taken along line AA.

FIG. 2 is a cross-sectional view for explaining the operation of the present invention;
(A) shows the related art, and (B) shows the present invention.

FIG. 3A is a plan view of a heat rail using a conventional cover plate. FIG. 3B is a side view showing a cross section taken along line AA.

FIG. 4 is a plan view of a heat rail prototyped before the present invention.

[Explanation of symbols]

 2 Heat Block 3 Recess 3a Tunnel 27 Cover Plate 27a Solder Supply Hole 27b Hole for Stirring and Spreading Melted Solder 27c Hole for Supplying Semiconductor Pellet 27d Slit (Opening) for Transfer Claw 28 Screen-like Member

Claims (2)

(57) [Claims] 1. A cover plate for a heat rail for forming a tunnel for transferring a lead frame by covering a concave portion of a heat block having a U-shaped cross section, wherein the cover plate for a heat rail is moved in a direction in which the lead frame is transferred. Along
To transport the lead frame with external claws.
A cover plate for a heat rail, wherein a screen-like member is provided upright at a slit end in a slit plate. 2. A heat rail cover plate for covering a concave portion of a heat block having a U-shaped cross section and forming a tunnel for conveying a lead frame, wherein the heat rail cover plate is moved in a direction in which the lead frame is conveyed. Along
To transport the lead frame with external claws.
A cover plate for a heat rail having a slit , the thickness of which is increased to at least 8 mm or more at a slit portion.