JPH0499361A - Lead frame - Google Patents

Abstract

PURPOSE:To prevent insufficient molding and voids in the mold by providing a lead frame with a plurality of resin pots having different volumes so as to fill up all cavities at substantially the same time irrespective of the distance of cavities from a cull. CONSTITUTION:Resin is supplied to a resin pot 2 through a gap that has a size of the thickness of a lead frame near a support bar 13. The time required for filling resin increases linearly with the distance of cavities 6 from a cull 3. To determine the volume of the resin pot, the deficiency in the furthest cavity from the cull is measured when the nearest cavity from the cull is filled up with resin. The deficiency should be equivalent to the volume of the resin pot communicating with the nearest cavity from the cull. The volume of each resin pot is determined according to the number of cavities. The furthest cavity from the cull does not need a resin pot.

Description

[Detailed Description of the Invention] [Summary] With regard to lead frames, resin sealing has been developed with the aim of preventing insufficient resin filling or cavities in packages due to the time difference in filling each cavity with resin. When the lead frame is stopped, the lead frame is connected to a plurality of pairs of cavities arranged through gates arranged in a row on runners extending from the cull, the lead frame having a plurality of resin reservoirs. ,
In addition, the volume of each resin reservoir is determined so that the filling time of the resin flowing into each cavity is equal to - regardless of the distance from the cull.

[Industrial application field]

The present invention relates to lead frames, and in particular, by providing a resin reservoir in the lead frame and making the filling time of the resin flowing into the cavity of each mold equal to This invention relates to a lead frame that does not have cavities.

In recent years, the use of semiconductor integrated circuits (ICs) has been remarkable, and the production volume of ICs has also increased dramatically. The importance of manufacturing technology in a series of manufacturing processes is increasing.

The assembly process involves cutting the wafer into chips, mounting them, bonding them, sealing them, and marking them. It has become the most important process that has the greatest impact on manufacturing costs.

In particular, the sealing process involves packaging to protect the element and take out the lead-out terminals, and various package forms and sealing methods are used, but because it is highly efficient in manufacturing and low in cost, Plastic packages that are sealed with resin using molding technology are often used.

However, as the number of leads pulled out from the pancage increases, the size of the package tends to increase, making resin encapsulation technology increasingly important.

[Conventional technology]

For resin encapsulation of semiconductor devices, for example, the chip is fixed on a mounting part called a stage, and a lead frame with gold wire or the like wire-bonded to terminal parts called inner leads is set in a sealing mold and sealed. This is done by pouring a stopper resin.

FIG. 3 is a perspective view of an example of a mold device for resin sealing.

In the figure, 1 is a lead frame, 11 is a cradle part, 12
is the stage, 13 is the support bar, 14 is the dam bar 15
3 is a lead, 3 is a cull, 4 is a runner, 5 is a gate, 6 is a cavity, 10 is a lower mold, 20 is an upper mold, and 30 is a mold device.

Resin encapsulation of semiconductor devices, like other electronic components, must be molded with precision and low molding pressure, so a type of transfer molding method using thermosetting resin such as epoxy resin is used. This is generally done by a certain low-pressure encapsulation molding method.

Therefore, the mold apparatus 30 shown in FIG. 3 is an example of a mold for transfer molding, and is composed of an upper mold 20 and a lower mold 10 that abut against each other.

For example, in the case of a semiconductor device, a lead frame 1 on which a chip is mounted is carried by a holder called a loading frame (not shown), and is placed between two molds 10.
．． 20 and resin sealing is performed.

The upper mold 20 includes a pot 2a (material chamber) for charging resin, heating it, melting it, softening it, plasticizing it, and pushing it into the mold.
is provided.

In the case of resin encapsulation of semiconductor devices and the like, so-called multi-piece molding, in which a plurality of molded products are obtained by one molding, is common. In that case, a cull 3 is provided continuous to the pot 2a via an injection hole called a sprue 2b.

The recesses (cavities in a broad sense) and protrusions (cores) that are drilled from the cull 3 are provided in the lower mold 10 and the upper mold 20 as appropriate depending on the shape of the molded product. 10
．． The structure is such that a desired molded product can be obtained when the two parts 20 are brought into contact with each other.

From this cull 3, a plurality of runners 4 (runners) are provided that radiate out in all four directions.

The resin heated and melted in the pot 2a to be softened and plasticized is first extruded to the cull 3 via the sprue 2b.

Next, the resin passes from the cull 3 through the runner 4, and finally fills each cavity 6 through the branched gate 5.

By the way, the molding process of thermosetting resin includes plasticization, shaping,
Curing takes place in three stages.

That is, in the transfer molding method, the resin in the first stage is first heated and plasticized in the bottle 2a to reduce its viscosity and become more fluid, and is then passed through the runner 4 and filled into the cavity 6. It is in the first stage of plasticization until it becomes plastic. Then, in the second stage, the resin is sufficiently filled to every corner of the cavity 6 and reaches a predetermined molding pressure.
The desired shape is imparted. After this, in the case of a thermosetting resin, a third stage of curing is performed, for example, by a chemical reaction such as condensation polymerization or addition polymerization.

In transfer molding, the third stage of curing begins after the second stage is completed when the resin is spread to every corner of all the multiple cavities 6 and the molding pressure is uniformly applied to all the cavities 6. is desirable.

However, as the number of molded products obtained in one molding process for mass production of ICs increases and the size of the package becomes larger, the size of the molding device 30 also increases, and the runner 4 also becomes longer. The number of cavities 6 has also increased and the volume has increased.

Therefore, there is a time difference between the cavity 6 near the center near the cull 3 and the cavity 6 in the peripheral part away from the cull 3 until every corner is filled with resin.

Then, the flow of the resin in the cavity 6 near the cull 3, which is filled quickly, stops before a predetermined molding pressure is sufficiently applied. Then, due to the nature of the thermosetting resin, curing begins quickly.

As a result, insufficient resin filling occurs in the cavity 6, and voids often occur in the molded product.

In response to this, conventionally, there is a multi-pot mold device in which the number of bots 2a is increased in proportion to the number of cavities 6, for example. However, there is a limit to the number of molded products that can be obtained in one molding process, and this has not been an efficient solution.

[Problem to be solved by the invention]

As described above, as the size of the mold increases, and as a result, the number of cavities and the volume increase, the time required to fill with resin differs between cavities close to the cull and cavities separated from the cull.

Therefore, although sufficient molding pressure is not yet applied to the cavity in the peripheral area away from the cull because it is still being filled with resin, the flow of resin has already stopped in the cavity in the center near the cull and curing has begun. A situation like this occurs.

Therefore, in the central cavity near the cull,
There have been problems in that curing proceeds with insufficient molding pressure, resulting in insufficient resin filling, and that as the resin hardens, there is no place for air to escape, creating cavities in the molded product.

Therefore, the present invention provides a lead frame in which a resin reservoir with a capacity gradient is provided in the lead frame set in each cavity so that the resin filling time for each cavity is equal to X. It is an object.

[Means for solving the problem] The problem described above is that when resin-sealing, the leads are connected to multiple pairs of cavities arranged through gates arranged in rows on runners extending from the cull. A frame, the lead frame comprising:
It has a plurality of resin reservoirs, and the volume of each resin reservoir is determined so that the filling time of the resin flowing into each of the cavities via the gate is equal regardless of the distance from the cull. The solution is a lead frame that is constructed to be

[Function] The resin to be filled into the cavity flows sequentially through the gates arranged in the runners connected from the cull, so the resin filling time is shorter for the cavity closer to the cull (and longer for the cavity farther away from the cull). While there is a time difference,
In the present invention, the resin filling time of each cavity is made equal.

That is, a plurality of resin reservoirs are provided in the lead frame, and the resin that has flowed into the cavity is collected in the resin reservoirs.

The volume of this resin reservoir is large because resin easily flows into the cavity close to the cull and filling is completed in a short time.
It is designed to have a large capacity to extend the filling time. As the cavity moves away from the cull, it becomes increasingly difficult for the resin to flow in and it takes a long time to fill the cavity, so the volume of the resin reservoir is made to gradually become smaller.

In this way, by creating a volume gradient in the resin reservoir and making sure that each cavity is filled with resin for the same amount of time, it is possible to prevent insufficient resin filling, which tends to occur especially in packages molded with cavities close to the cull. Cavities can be prevented.

[Embodiment] FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is an enlarged perspective view of the main part of FIG.

In the figure, 1 is a lead frame, 11 is a cradle part, 12
is the stage, 13 is the support bar, 14 is the dam bar 15
is the lead, 2 is the resin reservoir, 3 is the cull, 4 is the runner, 5
is a gate, 6 is a cavity, and 10 is a lower mold.

The lead frame 1 is made of a Fe-based or Cu-based alloy, and is made by punching or etching a strip of about 0.2 mm, for example.

The structure of the lead frame 1 is such that it is surrounded by a cradle part 11, and a stage 12 on which a semiconductor chip is mounted in the central part is supported by a support par 13 and is provided one step lower.

Further, a plurality of glue portions 15 are disposed toward the stage 12 across the dam bar 14 that prevents resin from flowing out during resin sealing.

A resin reservoir 2 is bored from the vicinity of the support bar 13 toward the cradle portion 11.

On the other hand, in the lower mold 10, a plurality of gates 5 are provided on a runner 4 extending radially from the cull 3, and a plurality of cavities 6 are provided through each of the gates 5.

The lead frame 1 is formed by a lower die 10 and an upper die 20.
The dam bar 14 is supported so as to be sandwiched between the boundary inner walls of the cavity 6 near the inside thereof. Therefore, there is a gap equal to the thickness of the lead frame l between the lower die 10 and the upper die 20 that are abutted together.

Therefore, resin flows into the resin reservoir 2 from the vicinity of the support par 13 through a gap equal to the thickness of the lead frame 1.

Incidentally, the time required for filling each cavity 6 with resin increases linearly as the cavity 6 is gradually separated from the cavity 6 closest to the cull 3.

So, to determine the volume of each resin reservoir 2,
First, when the cavity 6 closest to the cull 3 has been filled, the volume of the resin underfill that occurs in the cavity 6 furthest from the cull 3 is checked. Then, this volume is taken as the volume of the resin reservoir 2 of the lead frame 1 which is horizontally suspended in the cavity 6 closest to the cull 3. The volume of the resin reservoir 2 is gradually reduced in accordance with the number of cavities 6. It is not necessary to provide the resin reservoir 2 in the lead frame 1 that is horizontally suspended in the cavity 6 that is farthest from the cull 3.

In this way, the time for filling each cavity 6 with resin can be made equal.

In the knee, the resin reservoir 2 is provided in the cradle portion 11 of the lead frame 1, but the resin reservoir 2 is not limited to the cradle portion work 1 as long as there is another area to be provided.

Further, the processing of the resin reservoir 2 on the lead frame 1 can be carried out simultaneously when the strip is punched out, or it may be processed after the length of the sheet unit.

Furthermore, in the case of etching, it is more efficient to simultaneously process each sheet, for example.

〔Effect of the invention〕

According to the present invention, by providing a resin reservoir in the lead frame without adding anything to the conventionally used mold, the filling time of the resin flowing into each cavity can be made equal. Can be adjusted.

As a result, it is possible to prevent insufficient resin filling and the formation of cavities, which tend to occur particularly in the central cavity near the cull.

Therefore, the present invention greatly contributes to improving the yield in the sealing process of resin-sealed semiconductor devices and the like.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention; Figure 2 is an enlarged perspective view of the main parts of Figure 1; FIG. 3 is a perspective view of an example of a mold device for resin sealing. In the figure, l is lead frame, 2 is a resin reservoir, 4 is lunch, 6 is the cavity, It is. 11 is the cradle part, 3 is Cal, 5 is the gate, 1 Lead Me The key part of Figure 1 is the shellfish figure. Figure 2 Akira this year/) Oblique view of Mekushri r+ 1st layer Jugetsusha size JIJ mold 1biV -f1 for Kaizi 3 diagrams

Claims (1)

[Claims] When sealed with resin, the runner (4) extends from the cull (3).
A lead frame (1) that is connected to a plurality of pairs of cavities (6) through gates (5) arranged in a row, the lead frame (1) having a plurality of resin reservoirs. (2
), and the volume of each of the resin reservoirs (2) is such that the filling time of the resin flowing into each of the cavities (6) is approximately equal regardless of the distance from the cull (3). A lead frame characterized in that it is determined by.