JP4537620B2 - Lead frame with runner through hole - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a through hole of a lead frame and a runner arrangement end surface for removing runners and gates attached to a lead frame after resin-sealing a semiconductor device.
[0002]
[Prior art]
Conventionally, as a lead frame on which a semiconductor chip is mounted and resin-sealed, a lead frame in which mold parts are arranged in a single row on a single lead frame or a matrix frame in which mold parts are arranged in a plurality of rows has been used. In such a lead frame, a runner is disposed between adjacent mold parts so as to cross the lead frame, and a gate connected to the runner is connected to each mold part to perform resin sealing. Then, in the case of the matrix frame, a large number of packages can be formed at a time, and the productivity of the package can be increased and the manufacturing efficiency can be improved.
[0003]
However, since the runner is disposed long so as to cross the lead frame, it is difficult to peel off the residual resin adhering by curing in the runner and the gate after sealing with the resin. In view of this, the present applicant previously proposed in JP-A-3-184351 that a lead insertion frame is provided with a pin insertion hole for peeling off the residual resin from the surface opposite to the resin adhesion surface. Further, in Japanese Patent Application Laid-Open No. 5-206353, a punch contact protrusion integrated with the residual resin is used to peel and remove the residual resin that is cured and adhered to the lead frame in the runner and the gate from the side opposite to the resin adhesion surface. It was also suggested to drill a formation hole.
[0004]
However, in recent years, lead frames used in semiconductor packages typified by QFN (Quad Flat Non-Lead) have exposed leads, so a drop-off preventing structure with a cross-sectional shape that does not drop the leads on the back of the package has been adopted. ing. Therefore, the lead frame cannot be removed by a stamping process which is a normal punching process, and is formed by an etching process. In recent years, many etching processes have been performed in order to easily cope with changes in internal patterns due to short delivery times or for small-scale production such as trial production.
[0005]
[Problems to be solved by the invention]
However, when etching is performed on the lead frame to provide a through hole, etching is performed from both sides, so that the through hole 1 is constricted in the middle and has a projection inward as shown in FIG. . Therefore, when resin sealing is performed using such a lead frame, a phenomenon occurs in which the resin bites into the through hole 1 and is difficult to remove. In particular, in the case of a matrix frame in which runners are arranged so as to cross the lead frame, it is very difficult to perform runner removal and gate break by thrusting with a thrust pin or the like from the opposite side of the lead frame from the runner adhesion surface. That is, in the conventional stamping process, the resin in the runner push-through hole is pulled out at 500 g / hole. However, in the runner push-through hole 1 by the etching process, the resin in the hole is caught by the protrusion, so that it cannot be pulled out with such a small force. It requires a very large force of 5 kg / hole. In addition, 2 is a lead frame with a plate thickness of about 0.125 to 0.25 mm, 3 is a runner, and 4 is a runner thrust pin.
[0006]
In this manner, when the runner 3 on the lead frame 2 and the residual resin that hardens and adheres in the gate are pierced using a much larger force than before, the residual resin is forcibly peeled off from the lead frame 2, so that the package In rare cases, chipping or damage of the residual resin, deformation of the lead frame 2 or the like occurs. Also, for cost reduction, high integration per lead frame must be achieved, the package interval must be narrowed, the diameter of the runner thrust through hole must be reduced, and a pin thinner than the conventional runner thrust pin diameter must be used. . For example, the diameter of the hole is 2.2 mm and the diameter of the pin is 1.2 mm, but the diameter of the hole is required to be 1.2 mm. Therefore, there is a conflicting problem of insufficient strength of the runner thrust pin.
[0007]
In addition, in the case of high integration, the package interval in the width direction of the lead frame is narrowed to increase the number of packages. Therefore, if there is no runner punch through hole near the gate near the package, it will harden and adhere in the runner and gate. The residual resin cannot be peeled off well. Therefore, if there is no runner thrust through hole near the gate closest to the package, it is necessary to increase the number of runner thrust pins according to the number of packages, and the force of the runner and the entire gate peeling mechanism must be increased. .
[0008]
The present invention has been made paying attention to such conventional problems, and it is difficult to cause chipping, damage, deformation of the lead frame, etc. in the residual resin in the package or runner and the gate. It is an object of the present invention to provide a lead frame having a runner push-through hole that enables high integration of packages per lead frame.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in a lead frame having a runner push-through hole according to the present invention, a runner is disposed between adjacent mold parts on the lead frame, and a gate connected to the runner is connected to each mold part. The runner pierced through hole is formed by etching to pierce the runner of the lead frame that is resin-sealed and the residual resin that hardens and adheres in the gate from the side opposite to the resin adhesion surface. Then, the hole diameter provided on the resin adhering surface of the runner push-through hole is increased, the hole diameter provided on the opposite surface is reduced, and the runner placement end face of the lead frame is etched to provide resin adhering with the runner push-through hole. The opposite surface of the surface is formed as an inclined surface protruding sideways. Further , when the lead frame is etched, the size of the hole in the masking film covering both sides of the lead frame is changed so that the cross-sectional shape of the inner lead for the QFN type semiconductor package is larger on the package side and smaller on the non-package side. To form.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a plan view showing a state in which a QFN type semiconductor package matrix frame having a runner push-through hole to which the present invention is applied is opened after resin sealing. The matrix frame 5 has a larger number of mold parts on which semiconductor chips are mounted than in the prior art in order to achieve high integration of package formation per lead frame 6, and, for example, in the figure of this embodiment, there are five rows. Then, runners 7 (7a, 7b, 7c) are arranged so as to cross the lead frame 6 in the middle of adjacent mold parts on the lead frame 6 by a mold, and the gates 8 branched from the runners 7 are connected to the gates 8 respectively. Each package 9 is formed by connecting to the mold part and resin-sealing the mold part for six rows at a time. In addition, 10 (10a, 10b, 10c) is a cull connected to each corresponding runner 7.
[0011]
When each package 9 is formed on the matrix frame 5 in this way, the residual resin that is cured and adhered in each runner 7 and gate 8 after mold opening is opposite to the resin adhesion surface, in FIG. It must peel off from the top. Therefore, the lead frame 6 is previously drilled with a runner push-through hole 11 through which the residual resin protrudes and peels off at the gate branching location indicated by the dotted line of each runner 7. At that time, the hole is formed by changing the size of the hole of the masking film covering the upper and lower surfaces of the lead frame 6 up and down, or changing the concentration of the etching solution up and down.
[0012]
Then, as shown in FIG. 2, the hole diameter provided in the resin adhesion surface of the runner thrust through hole 11 can be increased, and the hole diameter provided on the opposite surface can be reduced. In particular, as shown in FIG. 3, the hole diameter of the runner push-through hole 11 may be sequentially decreased from the resin adhesion surface toward the opposite surface.
[0013]
At the time of peeling, the runner thrust pin 12 is moved in the direction of the arrow from the lower surface side of the lead frame 6 as shown in FIG. Then, the runner push-through hole 11 increases the hole diameter provided on the resin adhesion surface and decreases the hole diameter provided on the opposite surface, thereby reducing the resistance to removing resin in the hole. Therefore, the pin 12 is inserted into the hole. When the resin is pressed, the residual resin cured and adhered in the runner 7 and the gate 8 can be peeled off from the upper surface with a small force. Moreover, since the residual resin can be peeled off with a small force, the residual resin in the package 9, the runner 7 and the gate 8, the lead frame 6 and the like are not subjected to excessive force, and the residual resin in the package 9, the runner 7 and the gate 8 Chipping, damage, deformation of the lead frame 6 and the like are unlikely to occur. In particular, when the hole diameter of the runner push-through hole 11 is gradually reduced from the resin adhesion surface to the opposite surface, the runner push-through hole 11 is further improved. In the case of QFN, the cross-sectional shape of the inner lead 13 is large on the package side so that the inner lead 13 does not fall off.
[0014]
Since the residual resin can be peeled off with a small force when the runner thrust through hole 11 is formed in this manner, the diameter of the runner thrust pin 12 can be reduced. Therefore, the diameter of the runner push-through hole 11 can be reduced, and the hole position can be provided at the gate branching location of the runner 7 in the immediate vicinity of the package 9. However, since it is not preferable that the diameter of the runner thrust pin 12 is 1.2 mm or less in terms of strength, when the diameter of the runner thrust through hole 11 is 1.2 mm or less, the tip of the pin 12 is tapered. To do. If the hole diameter of the runner thrust through hole 11 is increased on the resin adhesion surface and the hole diameter provided on the opposite surface is decreased so that the residual resin is peeled off with a small force, the per runner 6 per Not only can the package 9 to be provided be highly integrated, but also the lead frame 6 can be widened, which is advantageous.
[0015]
In the above-described embodiment, the resin adhering surface is formed by etching the runner through-holes 11 that are peeled off from the side opposite to the resin adhering surface by curing the residual resin that is cured and adhered in the runner 7 and the gate 8 of the lead frame 6. Although the case where the hole diameter provided in the lead frame 6 is made larger and the hole diameter provided on the opposite surface is made smaller is explained, the runner arrangement end face 14 through which the runners 7 extending from the respective calves 10 of the lead frame 6 pass is etched. As shown in FIG. 5, it is preferable that the opposite surface (lower surface) 16 is formed on an inclined surface projecting a length L laterally from the resin adhesion surface (upper surface) 15 provided with the runner push-through hole 11. In particular, as shown in FIG. 6, the runner arrangement end surface 14 may be a smooth surface with a constant inclination angle.
[0016]
When such a runner-arranged end surface 14 is formed on an inclined surface by etching, the upper and lower positions of the masking film covering the upper and lower surfaces 15 and 16 of the lead frame 6 are shifted. When the runner arrangement end face 14 of the lead frame 6 is formed on an inclined surface projecting the lower face 16 laterally from the upper face 15, the peeling resistance is reduced, and therefore, the runner thrust pin 12 extends from the lower face 16 side of the lead frame 6 at the time of peeling. Is inserted into the hole 11 and the resin is pushed toward the upper surface 15, whereby the residual resin cured in the runner 7 and adhering to the end surface 14 can be peeled off from the end surface 14 with a small force. At that time, as shown in FIG. 4, a runner pusher 17 made of a block, a pin, or the like is provided near the runner arrangement end face 14 and moved in the direction of the arrow to push the residual resin near the end face 14. The runner pusher 17 may push the residual resin in the cal 10 together with the runner 7.
[0017]
Therefore, the residual resin cured in the runner 7 and the gate 8 and adhering to the upper surface 15 and the end surface 14 can be peeled off with a smaller force. Accordingly, excessive force is not applied to the residual resin in the package 9 and the runner 7 and the gate 8 and the lead frame 6, and the residual resin in the package 9 and the runner 7 and the gate 8 is chipped and damaged, and the lead frame 6 is deformed. Etc. are unlikely to occur. In particular, the runner arrangement end face 14 is preferably a smooth surface with a constant inclination angle.
[0018]
In addition, although the runner thrust pin 12 was inserted into the inside of the hole 11 and the runner thrust through hole 11 and the runner arrangement end face 14 were peeled off in the above embodiment, the hole shape of the runner thrust through hole 11 is described. The same effect can be obtained when applied to a runner push-through hole in which the protrusion is pierced with a punch and the residual resin is peeled off.
[0019]
【The invention's effect】
According to the present invention described above, the runner piercing through hole is etched to increase the hole diameter provided on the resin adhesion surface and reduce the hole diameter provided on the opposite surface, thereby reducing the resistance of the resin in the hole. be able to. Also, the run-off end face of the lead frame is formed by an etching process on the inclined surface that protrudes laterally from the resin adhering face provided with the runner piercing through hole, thereby reducing the peeling resistance of the runner placement end face. can do. Therefore, the residual resin that hardens and adheres in the runner and gate can be peeled off with a small force, and no excessive force is applied to the package, the residual resin that adheres and adheres in the runner and gate, the lead frame, etc. Further, it is possible to reliably suppress the occurrence of chipping or damage of the package or residual resin, deformation of the lead frame, etc. A wide lead frame can be used, and high integration of packages per lead frame can be achieved.
[0020]
Further, when etching the lead frame, the size of the hole in the masking film covering both sides of the lead frame is changed so that the cross-sectional shape of the inner lead for the QFN type semiconductor package is larger on the package side and smaller on the non-package side. By forming in this way, the inner lead has a cross-sectional shape that does not drop off from the package when the residual resin is peeled off, so that the deformation of the lead frame can be more reliably suppressed.
[Brief description of the drawings]
FIG. 1 is a plan view showing a state where a QFN type semiconductor package matrix frame having a runner push-through hole to which the present invention is applied is opened after resin sealing.
FIG. 2 is a cross-sectional view of a main part showing one shape of a runner push-through hole formed in the lead frame of the matrix frame for the QFN type semiconductor package by etching and residual resin in the runner integrated with the resin filled in the hole; It is.
FIG. 3 is a cross-sectional view of a main part showing another shape of a runner push-through hole formed in the lead frame of the matrix frame for the QFN type semiconductor package by etching and residual resin in the runner integrated with the resin filled in the hole; FIG.
FIG. 4 is a cross-sectional view of the principal part showing a state immediately before the runner hits the matrix frame for the QFN type semiconductor package;
FIG. 5 is a cross-sectional view of an essential part showing a shape of a lead frame of the matrix frame for the QFN type semiconductor package having a runner arrangement end face formed on an inclined surface by etching and a resin adhesion surface provided with a through hole with the runner. FIG.
FIG. 6 is a main portion showing another shape of the lead frame of the matrix frame for the QFN type semiconductor package in which the runner arrangement end face is formed into an inclined surface by etching and a resin adhering surface provided with the through hole with the runner; It is sectional drawing.
FIG. 7 is a cross-sectional view showing a main part of a conventional QFN type semiconductor package matrix frame immediately before a runner is pushed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 5 ... Matrix frame 6 ... Lead frame 7 ... Runner 8 ... Gate 9 ... Package 10 ... Cal 11 ... Runner thrust through hole 12 ... Runner thrust pin 14 ... Runner arrangement end surface 15 ... Resin adhesion surface (upper surface) 16 ... Opposite surface (lower surface) )

Claims (1)

A runner is placed between adjacent mold parts on the lead frame, and a gate connected to the runner is connected to each mold part and resin-sealed lead frame runner and residual resin that hardens and adheres in the gate. In a lead frame having a runner push-through hole that is formed by etching a runner push-through hole that protrudes and peels from the surface opposite to the resin-attached surface, the hole diameter provided on the resin adherent surface of the runner push-through hole is increased, the smaller the hole diameter is provided on the opposite side, the runner placement end surface of the lead frame by etching, to form the opposite side from the resin adhesion surface having a runner pushing through hole on the inclined surface projecting laterally further during the etching process of the lead frame, the large holes in the masking film covering each of both surfaces of the lead frame By changing the Is, it increases the inner leads of the cross-sectional shape of a QFN type semiconductor package is the package side, a lead frame having a runner pushing through holes and forming such a non-package side is reduced.

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