JPH07161954A - Cavity case for solid-state image pick-up element - Google Patents

Abstract

PURPOSE:To avoid a bad sensitivity which is to be caused by the fact that a thin burr is formed on the surface of inner leads when forming a case and the burr peels off and then attches to a pellet, etc., by preventing the thin burr from being formed on the surface of the inner leads when forming the case. CONSTITUTION:In a cavity case which is constituted of a lead frame 102 and molding resin 101, a thick burr 101a is formed on the upper surface except for tips 102b' of inner leads 102b. When forming a cavity case of this structure, a space is preliminarily formed in a part to correspond to the thick burr 101a of a molding die. Since the thick burr which, unlike a thick burr, hardly peel off, is formed at a place where a thin burr has been easily formed, the exfoliation of a burr is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device package structure, and more particularly to a structure of a plastic cavity case.

[0002]

2. Description of the Related Art FIG. 5 (a) is a plan view of a conventional plastic cavity case of this type, and FIG.
[Fig. 4] is a sectional view taken along line BB. Further, FIG. 6 is a cross-sectional view showing a state of the cavity case at the time of molding. To form this kind of cavity case, as shown in FIG. 6, a lead frame having an island 202a and an inner lead 202b is set between an upper mold 208 and a lower mold 209, and after the mold is clamped, the mold is closed. Thermosetting resin is injected into the cavity, and then the injected resin is cured.

As shown in FIG. 5, the cavity case is composed of a mold resin 201 and a lead frame 202. The mold resin portion is formed in a substantially box shape so that the solid-state image sensor can be mounted in the cavity of the case. In the case, the upper surface of the lead frame is exposed so that pellets can be mounted and wire bonding can be performed [FIG.
In (a), the clamp range is indicated by a broken line C]. The upper end of the upper opening of the molding resin 201 is formed with a step so that the transparent cap can be positioned and attached. In addition, the island 20 of the lead frame 202
The lower surface of 2a and the lower surface of the inner lead 202b are exposed so that they can be heated during bonding. In the conventional cavity case forming method, 10 μm is formed on the upper surface of the inner lead 202b other than the tip portion.
An undesired thin burr 201a of m or less is likely to be formed.

FIG. 7 (a) is a plan view showing another conventional example, and FIG. 7 (b) is a partially enlarged view of a region A surrounded by the broken line. The planar shape of the one-dimensional solid-state imaging device pellet is a very elongated rectangular shape with a width of 1 mm or less and a length of more than 30 mm.
The second island 202a also has a very elongated rectangular shape. When a cavity case is molded with a thermosetting resin, the coefficient of thermal expansion between the lead frame 202 made of metal and the mold resin 201 of the cavity case is usually molded and cured at a high temperature of 170 ° C. or higher. After molding, the side surface of the island 202a is peeled off from the mold resin 201 due to the difference between the two, and a large warp occurs on the island 202a. In the conventional example shown in FIG. 7, in order to prevent this warpage, the shape of the island 202a is formed in a wave shape to relieve the bending stress.

[0005]

In the above-mentioned conventional example,
Undesirable thin burrs are formed on the upper surface of the inner lead. Therefore, when pellets are mounted in the cavity case and assembled into a solid-state image pickup device, the thin burr 201a is dropped off due to mechanical vibration, thermal influence, etc., and the dropped thin burr constitutes the pellet surface or the case. However, there is a problem in that it adheres to the transparent cap and causes poor sensitivity or uneven sensitivity of the solid-state imaging device.

Such thin burr is formed as shown in FIG.
This is because the entire inner lead portion is not completely clamped at the time of resin molding, as shown in FIG. Therefore, in order to prevent the occurrence of thin burrs, it is sufficient to completely clamp the inner lead portion and the island portion by the upper mold 208 and the lower mold 209. In order to do so, Since the area to be clamped is increased and a large amount of pressure is required for mold clamping, the capacity of the 200 ton press which is commonly used at present is insufficient. Further, when the inner lead portion and the island portion are completely clamped, the resin at the bottom of the cavity case is formed only by the thickness of the lead frame, which makes the structure extremely fragile.

As a method for preventing the occurrence of this thin burr, in JP-A-63-299368, a gap between the inner leads of the lead frame is filled with a thermoplastic resin, and then the outer shape of the cavity case is formed. A method of resin molding has been proposed. Also, JP-A-61-144
Japanese Patent No. 032 proposes a method of preventing the occurrence of thin burrs by applying a soft metal coating on the surface of the lead frame. However, the former requires a new mold for filling gaps, and further has the inconvenience of a two-step resin molding process, while the latter requires a considerably high plating cost for applying a soft metal coating and leads There is a drawback that the price of the frame becomes considerably expensive, and in any case, it goes against the purpose of using the cavity case for the solid-state image pickup device made of plastic for the purpose of cost reduction.

Further, when the island has a corrugated plane as shown in FIG. 7, the lead frame 2 made of metal is used.
02 and the mold resin 201 cause a minute gap 211 to occur at the interface between the island 202a and the mold resin 201. When the back surface of the cavity case is sealed with the back surface sealing resin, this minute gap 211 is generated. There is a problem in that the sealing resin leaks from the gap 211 into the hollow portion of the cavity case, stains the pellet and the transparent cap, and causes poor sensitivity of the solid-state imaging device.

Therefore, the first object of the present invention is, firstly, without using a press having a large pressurizing capability.
It is to prevent the occurrence of thin burrs without causing structural weakness in the case and without increasing the cost. Secondly, the plane shape of the island is made wavy. The other is to prevent the island from separating from the mold resin and prevent the backside sealing resin from leaking into the case cavity. Then, the present invention achieves these things to prevent defective sensitivity and uneven sensitivity from occurring in the solid-state imaging device.

[0010]

In order to achieve the above object, according to the present invention, the leads (102a, 102b) of the lead frame (102) are made into a box-shaped molding resin (10).
Inner lead (102b)
The lower side except the tip of is buried in the mold resin,
Provided is a cavity case for a solid-state imaging device, the upper surface of which is covered with a thick burr (101a) of a mold resin.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. [First Embodiment] FIG. 1A is a plan view showing a lead unmolded state after pellets are mounted in a cavity case of a first embodiment of the present invention and a sealing step is completed. Figure 1
(B) is sectional drawing of the AA line. The feature of the cavity case of the present embodiment is that the inner lead 102a is
That is, the surface other than the tip portion of the is covered with the thick burr 101a.

FIG. 2 is a sectional view showing a state when the cavity case of this embodiment is molded. First, as shown in the figure, the tip portion 10 of the island 102a of the lead frame 102 and the inner lead 102b.
2b 'is clamped by the upper die 108 and the lower die 109 of the forming die. Here, the inner lead 10 of the upper mold 108
0.1mm to 0.3m on the part other than the tip of 2b
A gap 108a of m is formed. In this state, the sealing resin is injected after mold clamping and kept at 170 to 180 ° C. for several hours to cure the resin.

In the cavity case thus formed, the upper surface of the inner lead 102b other than the tip portion 102b 'is covered with a thick burr 101a of a mold resin having a thickness of 0.1 mm to 0.3 mm. The thick burr does not peel off even if mechanical vibration is applied because it is thick and integrated with other mold resin portions. Further, in the molding process shown in FIG. 2, since the clamped portions of the lead frame are limited to the tip portions of the island 102a and the inner leads 102b, it is possible to perform mold clamping with sufficient pressure by a conventional press.

The solid-state imaging device is assembled as shown in FIG. 1 using the cavity case thus formed. First, a resin adhesive (resin paste) 104 is applied onto the island 102a of the lead frame to form the pellet 1
03 is mounted and heated to cure the adhesive. This pellet mounting may be performed using Ag paste. Next, in the wire bonding step, the pad of the pellet 103 and the tip of the inner lead 102b are connected by a thin metal wire 105, and then a thermosetting or photocurable adhesive 107 is applied to the cavity case. The transparent cap 106 is closed to cure the adhesive. Next, the openings of the molding resin formed on the back surface of the island 102a and the back surface of the tip end portion of the inner lead 102b are filled with the back surface sealing resin 110 to obtain the state shown in the drawing. Then, lead molding is performed to complete the manufacture of the solid-state imaging device.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. Figure 3
It is sectional drawing which shows the resin molding process for forming the cavity case of a 2nd Example, and FIG. 4 is sectional drawing of the solid-state imaging device produced using the cavity case of a 2nd Example. As shown in FIG. 3, in the molding die forming this embodiment, the upper die 108 has a gap 108a on the island as well as a gap 108a on the inner lead.
And a gap 109a is provided below the island 102a of the lower mold 109. Here, the gap 108
The thickness of b and 109a is 0.1 mm to 0.2 mm. This thickness should be thin considering the transmission of ultrasonic waves and heat in the wire bonding process, but on the other hand, it should be set to the above value in consideration of preventing peeling of the mold resin. Has been done.

In the solid-state image pickup device shown in FIG. 4, parts common to those of the previous embodiment shown in FIG. 1 are designated by the same reference numerals, and a duplicate description will be omitted. In the cavity case of the present embodiment, as shown in the figure, in addition to the thick burr 101a on the inner lead 102b, the thick burr 101b having a film thickness of 0.1 to 0.2 mm is formed on the upper and lower surfaces of the island 102a. There is. In the previous embodiment, a minute gap may occur between the island 102a and the mold resin 101 due to the difference in thermal expansion coefficient between the island 102a and the mold resin 101 [see FIG. 7 (b)]. Then this fear disappears. Therefore, in the previous example, it was necessary to use a resin paste having a certain degree of viscosity so that the sealing resin would not leak into the cavity of the case through the gap, but in the present example, such consideration should be taken. There is no need to pay. Also, as shown in FIG. 4, the island 102a
The filling of the backside sealing resin itself can be omitted below.

The preferred embodiment has been described above.
The present invention is not limited to these examples, and various modifications can be made within the scope of the present invention described in the claims. For example, in the second embodiment, the gap 108b of the upper mold 108 is the island 102a.
Although it was formed only on the top, this can be widened to between the tips of the inner leads. Further, the thickness of the thick burr is not limited to the value in the embodiment.

[0018]

As described above, in the cavity case of the present invention, the upper surface of the portion other than the tips of the inner leads is covered with the thick burr of the molding resin. It suffices to clamp only the tips of the leads with a molding die, and it is possible to form a cavity case having a hollow structure with a molding press having a relatively small mold clamping pressure without the occurrence of thin burrs. Also, unlike the thin burr, the thick burr provided on the inner lead other than the tip part does not fall off due to mechanical vibration and thermal influence, and it may adhere to the pellet and the transparent cap like the thin burr. This eliminates the problem of poor sensitivity and uneven sensitivity of the solid-state imaging device after assembly.

Further, according to the second embodiment, the thick burr is also provided on the front surface and the back surface of the island, so that a gap caused by the difference in the coefficient of thermal expansion between the metal island and the cavity case molding resin is formed. It can be prevented from being generated, and the sealing resin can be prevented from leaking from the gap. Alternatively, it is possible to omit the resin sealing step itself on the back surface of the island.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of a solid-state image pickup device for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view for explaining a resin molding process of the cavity case according to the first embodiment of the present invention.

FIG. 3 is a sectional view for explaining a resin molding process of a cavity case according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a solid-state imaging device for explaining a second embodiment of the present invention.

FIG. 5 is a plan view and a sectional view of a conventional example.

FIG. 6 is a sectional view for explaining a conventional resin molding process for a cavity case.

FIG. 7 is a plan view and a cross-sectional view of another conventional example.

[Explanation of symbols]

 101, 201 Mold resin 101a, 101b Thick burr 201a Thin burr 102, 202 Lead frame 102a, 202a Island 102b, 202b Inner lead 102b 'Inner lead tip 103 Pellet 104 Resin adhesive 105 Metal fine wire 106 Transparent cap 107 Adhesive 108, 208 Upper mold 108a, 108b, 109a Gap 109 Lower mold 110 Backside sealing resin 211 Gap

Claims (5)

[Claims] 1. A cavity case for a solid-state image pickup device, wherein leads of a lead frame are integrated with a box-shaped molding resin, the lower side of the inner leads other than the tip portions is buried in the molding resin. A cavity case for a solid-state image sensor, characterized in that the upper side is covered with a thick burr. 2. The cavity case for a solid-state image pickup device according to claim 1, wherein the lead frame punched portion between the island and the tips of the inner leads and between the tips of the inner leads is filled with a mold resin. 3. The cavity case for a solid-state image pickup device according to claim 1, wherein the upper surface and the lower surface of the island and the upper surface and the lower surface of the tip of the inner lead are not covered with the mold resin. 4. The upper surface and the lower surface of the island are covered with a thick burr of the molding resin, and the space between the upper surface and the lower surface of the tip of the inner lead is not covered with the molding resin. A cavity case for a solid-state image sensor as described above. 5. The cavity case for a solid-state image pickup device according to claim 1, wherein the island has a corrugated planar shape.