JPH04245447A - Metal mold for semiconductor element resin sealing use - Google Patents

Abstract

PURPOSE:To reduce the size of a resin foreign substance remaining in a sealing resin layer and to reduce the bent and left amount of a gate by a method wherein the thickness of a sealing resin in the contact part between the flow passage of the sealing resin arranged so as to come into contact with the gate part and the gate part is increased. CONSTITUTION:A gate 12 is formed at the lower side than the central part of the thickness of a sealing resin layer 10, i.e., at the contact part with the tip of a molten-resin flow passage 11. Although the molten-resin flow passage 11 is hollow, its tip is matched directly to the small-diameter gate 12. As a result, a slope 13 is formed; the lower end is formed to be linear with the lower end of the gate. At this time, a slope (a) is worked; the dimensional tolerance of E is changed from 0.17mm+ or -0.005mm to 0.20mm+0.05mm to 0.20-0mm. At this time, the angle formed by the gate 12 and by the slope 13 of the flow passage 11 is changed from 35 deg. in conventional cases to 40 deg. or higher and up to 90 deg.; the pressure of a molten resin at the gate 12 is increased; an equally thick part whose diameter is small is eliminated; the bent and left amount of the gate is reduced.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION This invention relates to resin encapsulation technology for resin encapsulation type semiconductor devices, and in particular to transfer (Transfer) technology.
nsfer) is suitable for molding molds.

0002

[Prior Art] Transfer molding, which uses a mold, is widely used as a method for separating semiconductor elements from the external atmosphere.Special manufacturing equipment includes a so-called single pot and a tablet.
Generally, a semiconductor element to be sealed is processed by applying a molded sealing resin and applying a predetermined pressure and heat. A lead frame (Lead frame) is used to carry out this sealing process.
A plurality of cavities (Cavities) are provided to place the semiconductor device to be encapsulated mounted on the frame (Mount) in the mold, a gate (Gate) for allowing the sealing resin to flow into the cavity, and a gate (Gate) for allowing the encapsulation resin to flow into the cavity. Naturally, a passage for sealing resin toward each cavity is provided.

[0003] By the way, the sealing resin melted in the pot is once collected in Cal, then dispersed into the channel and flows into each gate, and after the resin has hardened, it is removed from the molding die into the channel. The resin-sealed semiconductor device was taken out in a state in which it was in close contact with the device, and then the resin-sealed semiconductor device was peeled off by hand while the flow path was fixed. Furthermore, in an automatic resin molding machine, a lead frame on which a resin-sealed semiconductor device is mounted is fixed, and then the two are separated by removing the lead frame with a jig. Next, the relationship between the sealing resin layer and the flow path in such a resin sealing process will be explained.

That is, in the cavity formed in the upper die constituting the pair of molds, thin metal wires are bonded to the semiconductor element to be sealed mounted on the lead frame and the electrodes necessary therefor. In addition, since a passivation layer and the like are formed, the thickness is larger than that of the lower mold. Moreover, the gate that allows the encapsulating resin to flow into the pair of molds is installed in a small size at the boundary between the two, and the lower end of the flow path that is continuous with this gate is naturally formed in a straight line with the lower end of the gate, so that the upper end and An inclined surface will be formed between the gates.

[0005] Through such a resin sealing process, a so-called super mini transistor (SuperMini Tar) is manufactured.
An ultra-small envelope (corresponding to the sealing resin layer) for a diode or a diode is also formed, and its shape is shown in the perspective view of FIG. That is, the rectangular envelope has a total length of 2.0 mm, a length of 1.25 mm, and a height of 0.0 mm.
It is extremely small, measuring 95 mm, and has lead terminals 2 and 3 electrically connected to the sealed semiconductor element drawn out from its side surfaces for connection to other equipment. The relationship between the flow path and the gate, which is essential for transfer molding, will be explained with reference to FIGS. 2 to 5. 2 and 4 are cross-sectional views taken along the Y-Y' line in FIG. 1, showing the state before the sealing resin and the gate tip are separated, and FIG. 3 is the gate tip seen from the side with the gate. Figure 5 is a side view after separation, and Figure 5 shows the state after separating the sealing resin and the gate tip.
FIG. Incidentally, the encapsulating resin layer 1 for a resin-encapsulated semiconductor device has a portion less than half its thickness, that is, a boundary between a pair of molds, an upper mold and a lower mold, and a place where a lead frame is arranged. As described above, the gate 4 is formed near the corresponding position. Moreover, the gate 4 is composed of a hole with an extremely small area, and its cross section is defined by the length E and the width D (see FIG. 3). Furthermore, to be more precise, the passage 5 through which the molten resin flows must be installed continuously to the gate 4.
Further, after the resin molding process, as is clear from each figure, a small diameter equal thickness part 6 is formed which is continuous with the flow path 5 and the gate 4. Furthermore, FIG. 5 shows a state in which the small-diameter, equal-thickness portion 6 is broken and resin remains.

[0006]

[Problems to be Solved by the Invention] When separating the sealing resin layer and flow path of a resin-molded semiconductor device after resin molding, gates may break in the sealing resin layer regardless of whether the work is done manually or automatically. The residue adhered to the envelope, causing inconveniences such as irregular shapes and dimensional deviations.

In particular, in a resin-sealed semiconductor device having an ultra-small envelope shown in FIG. 1, the ratio of the amount of gate remaining bending to the envelope becomes large, so it is difficult to reduce the amount of remaining gate bending. It was strongly requested. As a countermeasure, measures have been taken to reduce the E dimension of the small-diameter, equal-thickness section 6 formed continuously in the flow path 5 in contact with the sealing resin layer, that is, to reduce the gate 4, but if it is made too small, resin cavities From the viewpoint of moldability, it has not been possible to reduce the amount of remaining gate folding to zero because molding defects such as unfilling and unfilling occur. Furthermore, as another means, as shown by the dotted line in FIG.
Even if the maximum stress was applied to the tip of the gate 4 by increasing the stress, no significant effect was obtained.

[0008] The biggest difficulty is the occurrence of a uniform thickness portion 6 with a small diameter. This is because when manufacturing the gate part in the mold, the E dimension standard for gate 4 should be set to the standard value ±5μm in order to give priority to moldability.
It has been found that the process of scraping with a grindstone is performed because of the regulation, and as a result, a portion 6 of equal thickness with a small diameter inevitably occurs, which is the biggest factor in increasing the amount of unbent portion of the gate.

Due to the presence of the small-diameter, equal-thickness portion 6, protrusions as shown in FIG. 5 remain on the sealing resin layer, which causes trouble in the manufacturing equipment in the next process, and causes problems when shipped. In the mounting process on the printed circuit board, there is a pickup (Pick Up) mistake (Mi
ss) occurs.

The present invention was developed in view of the above circumstances, and is particularly aimed at reducing the amount of gate bending remaining.

[Configuration of the invention]

0012

[Means for Solving the Problems] A pair of molds, a cavity formed in one of the molds and in which a resin-sealed semiconductor element is disposed, a gate part installed corresponding to the cavity and into which a sealing resin flows, The present invention is characterized in that the size of resin irregularities remaining in the encapsulating resin layer is minimized by providing an encapsulating resin flow path disposed in contact with the gate portion and increasing the thickness of the encapsulating resin at the contact portion between the two. It has the characteristics of a mold for resin encapsulation of semiconductor elements.

[0013]

[Operation] The present invention has a shape that can minimize the occurrence of small-diameter, equal-thickness portions of the sealing resin layer when manufacturing a gate portion in a mold. In other words, when forming a gate part in a resin molding mold, the thickness of the tip part is approximately 1.18 mm thick compared to the conventional one.
It is enlarged twice, the length is changed from 0.10 mm to 0 mm, and the channel is brought into direct contact with the gate part. Moreover, by increasing the inclination angle of the tip of the flow path, which has a larger diameter than the gate, it is possible to remove the equal thickness portion that was conventionally formed in the polishing process using a grindstone. As a result, in terms of moldability, resin void defects and non-resin filling defects have been halved from 1,000 ppm to 500 ppm, and the incidence of resin-sealed semiconductor devices with gate folds has been reduced from 23% to 2%, almost 1%. /10, and the maximum length of the unbent portion of the gate is 0.25 mm.
It was found that the diameter was halved from 0.13 mm to 0.13 mm.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to FIGS. 6 to 12, and new numbers will be given to parts that are the same as those in the prior art to aid understanding. FIG. 6 is a sectional view taken along the Y-Y' line in FIG. 1, showing the sealing resin according to the present invention and the gate before separation, and FIG. 7 shows the sealing resin according to the present invention and the gate before they are separated. FIGS. 8a and 8b are cross-sectional views showing the state after separation of the gates by cutting FIG. 1 along the Y-Y'line; FIGS.
9 is a cross-sectional view and a top view showing a state in which the flow channel and the sealing resin layer are not formed in a straight line, FIG. 9 is a cross-sectional view of the sealing resin, gate, and flow channel that are the components of the resin molding mold, and FIG. 10 and Figure 1
1 is a cross-sectional view symmetrically showing the gate portion of a resin molding die in the prior art and the present invention, and FIG. 12 is a diagram showing the length of the gate unbent portion in the conventional technology and the present invention. That is, the resin-sealed semiconductor device formed according to the embodiment of the present invention is, for example, the super mini transistor or diode shown in the prior art section, and the resin-sealed semiconductor device is formed by so-called transfer molding using a pair of molds. The dimensions of the resin layer 10 are extremely small: length 2.0 mm x width 1.25 mm x thickness 0.95 mm. In the assembly process that precedes this molding process, the electrodes of the encapsulated semiconductor element mounted on the bed of the lead frame and the leads formed on the lead frame are connected using thin metal wires using a known bonding method. The thickness of the upper mold must be larger than that of the lower mold. Further, in order to provide a plurality of cavities in the upper mold in which the encapsulated semiconductor element subjected to such treatment is placed, and to allow the molten resin layer to flow into these cavities, a gate layer must naturally be formed. Therefore, the gate 12 is placed at the boundary between the pair of molds, in other words, at the bottom of the center of the thickness of the sealing resin layer 10, that is, at the contact area with the tip of the molten resin channel 11, as shown in FIGS. 6 and 7. Form. Recently, multi-pot type machines have been used specifically for transfer molding, which heat a tablet-shaped sealing resin and melt the resin under a certain pressure and heat, which is then collected in a cal. into each gate 12.

[0015] As the material for the lead frame, iron, iron-nickel alloys such as Farnico and Clad materials, copper, copper alloys, and copper clad materials can be used, and fine metal wire materials include Au, Al, etc. ,
and copper alloys for copper, copper alloys, or copper cladding materials. Incidentally, the molten resin flow path 11 is naturally formed in a hollow shape, but an inclined surface 13 is formed at its tip to directly match the small diameter gate 12, and its lower end is formed in a straight line with the lower end of the gate. However, the case where the flow path and the sealing resin layer are not linear is shown in the cross-sectional view and top view of FIGS. 8a and 8b. The dotted line in FIG. 8b is assumed to be a part of the lead frame 14, and the circle in the figure is a positioning pin (Pi
n) is a hole into which an inner lead 18 is shown in addition to the sealing resin layer 1.

By the way, FIG. 9 shows a part of the upper and lower molds, and the number of the lower mold is indicated by adding '' to that of the upper mold. That is, it is natural that the lead frame 14 on which the semiconductor element to be sealed is mounted is placed inside the upper and lower molds, and a portion 15 of the cavity portion where the sealing resin layer 10 is formed.
, 15', part of the gates 12, 12' and lead guide parts 16, 16', and further gates 12, 1.
Sub runners 17 and 17' forming a part of the flow path 11 are formed adjacent to the channel 2'. The arrow drawn in this figure indicates the direction in which the molten resin flows.

By the way, it is the gates 12 and 1 that determine whether or not a uniform thickness portion with a small diameter is generated when separated from the sealing resin layer 10.
2' shape, and in the conventional manufacturing stage of the mold, as shown in Fig. 10, the inclined surface a is machined and the dimensional tolerance of E is 0.17.
It was very difficult to keep it within the strict value of mm±0.005 mm. Therefore, after machining it to be smaller at first, the B side was ground with a whetstone to bring it within the E dimension tolerance. but,
0.02mm on gate 12 as shown in Figures 2, 4 and 5.
An equal thickness part with a small diameter of 0.15 mm was generated. However, in the present invention, the E dimension tolerance is 0.17 mm ± 0.005
mm to 0.20mm+0.05mm~0.20mm-
It was changed to 0mm. At this time, the lower end of the flow path 11 is connected to the gate 12.
, 12', and is formed in a straight line with the lower end of the gate 12'.
The angle formed by the inclined surface 13 of the flow path 11 was changed from the conventional 35° to 40° or more and up to 90°, increasing the pressure of the molten resin at the gate 12 and eliminating the uniform thickness part with a small diameter ( (See Figure 11). As a result, as shown in FIG. 12, it was found that the amount of remaining gate bending was reduced and the occurrence rate could be significantly improved. Furthermore, it was found that the resin shaping properties such as resin voids and unfilled areas were improved, and that the same thickness portions with small diameters did not occur as in the conventional method.

FIG. 12 shows the length of the uniform thickness portion generated in the gate on the vertical axis, and the number of generated portions on the horizontal axis for the conventional example and the present application. The amount of unbroken gates was only 21 at n=1000, which was a very significant improvement. In the above embodiment, only the case where the angle of the slope formed by the gate and the end of the flow path is 40 degrees is shown, but it should be noted that it goes without saying that the angle may be within 90 degrees.

[0019]

Effects of the Invention: According to the method of the present invention, the rate of occurrence of resin cavities and unfilling has been reduced from the conventional 1000 ppm to 500 ppm1.
/2, ■ The rate of occurrence of unbroken gates was reduced from 23% to 2% to 1/10, ■ The maximum amount of unbent gates (length) was 0.
A significant improvement was achieved, from 25 mm to 0.13 mm, about 1/2.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a resin-sealed semiconductor element.

FIG. 2 is a cross-sectional view of FIG. 1 taken along line Y-Y', showing a state before separation of a conventional envelope and a gate portion.

FIG. 3 is a side view of a conventional envelope after the tip is separated, as seen from the side where the gate is located.

FIG. 4 is a cross-sectional view of FIG. 1 taken along the line Y-Y', showing a state before separation of the conventional envelope and gate portion.

FIG. 5 is a side view of FIG. 1 taken along the line Y-Y' and showing the state after the gate part is separated from the conventional envelope.

FIG. 6 is a cross-sectional view taken along the line Y-Y', showing the state of the envelope and gate portion according to the present invention before they are separated.

FIG. 7 is a cross-sectional view taken along the line YY' and showing the state after separation of the envelope and gate portion according to the present invention.

FIG. 8a is a cross-sectional view showing a state in which the flow path and the sealing resin layer are not formed in a straight line. FIG. 8b is a top view showing a state in which the flow path and the sealing resin layer are not formed in a straight line.

FIG. 9 is a partial cross-sectional view of the gate and flow path of the resin mold component.

FIG. 10 is a sectional view showing a gate part of a conventional resin molding die and a gate part of a resin molding die according to the present invention in contrast.

FIG. 11 is a sectional view showing a gate part of a conventional resin molding die and a gate part of a resin molding die according to the present invention in contrast.

FIG. 12 is a diagram showing the length of the remaining amount of gate bending in the conventional method and in the present invention.

[Explanation of symbols]

1, 10: Sealing resin 2, 3: Lead terminal 4, 12, 12': Gate 5, 11: Channel 6: Equal thickness part with small diameter 6', 13: Inclined surface 14: Lead frame 15, 15': Cavity part 16, 16': Guide part 17, 17': Sub runner 18: Inner lead

Claims (1)

[Claims] 1. A pair of molds, a cavity formed in one of the molds and in which a resin-sealed semiconductor element is disposed, and a gate part installed corresponding to the cavity and into which the encapsulating resin flows.
It is characterized by comprising an encapsulating resin flow path disposed in contact with the gate portion, and by increasing the thickness of the encapsulating resin at the contact portion between the two, the size of resin irregularities remaining in the encapsulating resin layer is minimized. Mold for resin encapsulation of semiconductor elements.