JPH0377335A - Metal mold for resin seal - Google Patents

Abstract

PURPOSE:To make it unnecessary to change a size of a lead frame itself and to change a size of a metal mold according to a difference in a material by a method wherein a plurality of dividable cavity blocks are provided and a gap-variable means is installed at each gap. CONSTITUTION:A metal mold 1 is constituted of cavity blocks 5 while a cavity 4 in which a gate 10 installed so as to be faced from a runner 8 is opened is used as a unit. A gap-variable means 6 which is composed of a taper block 61 whose opposite two faces are not parallel and of a spring 62 which presses the cavity blocks 5 to a fixed block 11 is installed at each gap of the cavity blocks 5. When the taper block 61 is pushed into the gap between a grade of 1/40 in a longitudinal direction, and the cavity blocks 5, the gap is widened and when it is pulled the gap is narrowed.

Description

[Detailed Description of the Invention] [Summary] Regarding a mold for resin sealing, the purpose of this invention is to make the gap between individual cavity blocks variable according to the thermal expansion of the lead frame, and to create a lead on which multiple chips are mounted. A mold for resin-sealing a frame, the mold includes a plurality of divisible cavity blocks each having at least one cavity corresponding to each chip, and in a gap between each of the cavity blocks, A gap changing means for changing the gap between the cavity blocks is provided.

[Industrial application field]

The present invention relates to a mold for resin-sealing a semiconductor device.

In recent years, the development of semiconductor integrated circuits (ICs) has been remarkable, ICs are being used in all fields, and the production amount of ICs is increasing dramatically.

Along with this, the importance of manufacturing technology for a series of manufacturing processes from the wafer stage to the finished product as a semiconductor device is increasing.

In the FC manufacturing process, there is a so-called wafer process from the wafer stage to the formation of a large number of minute elements, cutting into chips, and fixing the chips to a frame-shaped terminal called a lead frame and cutting them into thin wires. In the wire bonding process, which connects wires using wafers, it is possible to improve productivity by increasing the size of the wafer, making the circuit pattern finer, increasing the bonder's connection speed, or automating the entire process. It is planned.

On the other hand, semiconductor devices generally require
Sealing is performed using various methods, but the manufacturing efficiency is high;
Resin encapsulation using molding technology is often used because of its low cost.

It is said that the price of an IC is determined by the encapsulation process, and the importance of the molding process, which includes resin encapsulation technology and mold manufacturing technology for the process, is increasing.

[Conventional technology]

Resin sealing of resin-sealed semiconductor devices involves, for example, setting a lead frame in which the chip is fixed on a mounting part called a header and wire-bonded with gold wire to terminal parts called inner leads in a sealing mold. This is done by pouring the sealing resin.

FIG. 2 is a perspective view illustrating a conventional molding die, and FIG. 3 is an enlarged view of the cavity in FIG. 2.

In the figure, a mold 1 is a mold base 7.
, a plurality of cavity blocks 5, for example, 10 or 20, which are fitted into the mold base 7 as nests, and passages through which the resin flows provided in each cavity block 5 and the mold base 7, that is. runner 8.

This cavity block 5 is constructed of a sheet-like lead frame 3 on which a plurality of chips 2 are mounted, wire-bonded, and cut into a predetermined length, and has a cavity 4 corresponding to each chip 2.
is provided as a void into which the sealing resin flows and is molded.

In Figure 3, only the mold 1 located on the lower side is shown,
The other mold that covers this is omitted, and
The lead frame 3 is made of iron, iron-nickel alloy, copper alloy, or the like, depending on the purpose.

During molding, a plurality of sheets of lead frames 3 on which chips 2 are mounted are held between loading frames 9, and are first preheated by heating means provided on a device called a bench stand (not shown).

Next, the lead frame 3 is attached to the loading frame 9
Each sheet-like lead frame 3 is conveyed onto the mold 1 while being held by the mold 1, and is set in the corresponding cavity block 5, where resin sealing is performed.

Through this series of operations, the lead frame 3 has a diameter of 160~
The lead frame 3 is heated to a high temperature of 180° C., and depending on the material of the lead frame 3, a dimensional difference occurs due to a difference in coefficient of thermal expansion.

On the other hand, the mold 1 used for encapsulating a semiconductor device is usually
Made of tool steel.

Comparing the thermal expansion coefficients, the steel molds have
11.6X10-"/'C1 Among the materials constituting the lead frame, iron-nickel alloys have a
X 10-6/”C, 17.0X10 for copper alloy
-'/"C.

The size of each cavity in the mold that corresponds to each chip is small, such as 10m or 20mm, and the spacing between the cavities is 20mm or 30n+.
Since the value is m, the size of the expansion ΔP between the cavities due to thermal expansion of the lead frame is within a negligible range.

However, for example, if the length of one sheet of a lead frame on which n chips are mounted is 150IIII and the temperature of the mold is 175°C, the temperature difference from the room temperature of 25°C will be 150°C.

Therefore, when calculating the thermal expansion ΔPXn under these conditions, in the case of a lead frame made of prepared alloy, it is 17.0x
lO-bx150 x150 =0.3825 (mm
), and for a lead frame made of iron-nickel alloy, 4,5 xlO-'x150 x150 = o,
1 oia (accommodation), which is a large value that cannot be ignored.

Therefore, the dimensions of the mold and lead frame are made to be relatively different at room temperature so that they have the same dimensions in a heated state.

Moreover, between the two types of glue and Dofray J4, which are made of different materials, the difference is 0.2812 mI! The size difference of 1 is a problem.

Therefore, in order to improve the thermal characteristics of semiconductor devices with the same external shape, lead frames made of copper-based alloy materials are added, and iron-based alloys are added to improve mechanical strength.
When attempting to use a new lead frame made of a nickel-based alloy material, it is necessary to change the dimensions of the node frame itself or to change the dimensions of the mold to match the thermal expansion coefficient of the lead frame.

By the way, in the manufacturing process of semiconductor devices, the molds used in the manufacturing process because the dimension Tn degree is a problem include a mold for punching the lead frame (room temperature), a mold for resin sealing ( 160 to 180°C), and a mold for cutting and bending the resin-sealed lead frame (
room temperature), etc.

Among these, only the mold for resin sealing is used under heating conditions.

In other words, when changing the material of the lead frame, it has conventionally been necessary to prepare multiple types of molding dies.

[Problems to be Solved by the Invention] As described above, even if the molding dies used in the conventional resin encapsulation process have the same external shape, the materials of the lead frames differ. It was necessary to prepare a mold compatible with the lead frame.

In other words, if a copper-based alloy material is used to improve thermal properties, or an iron-nickel alloy material is used to improve mechanical strength, the thermal expansion coefficients of the two materials Because of the different coefficients of thermal expansion, it was necessary to change the dimensions of the lead frame itself or the dimensions of the mold to match the respective coefficients of thermal expansion.

This has resulted in an increase in mold replacement work and mold equipment costs, resulting in a significant reduction in the efficiency of the resin sealing process.

The present invention makes it possible to individually divide the cavity blocks of the mold so that the gaps between them can be varied, and depending on the material of the lead frame, the dimensions of the lead frame itself or the dimensions of the mold can be changed. The purpose is to provide a mold for resin sealing that does not require new installation.

[Means for Solving the Problems] The problem described above is a mold for resin-sealing a lead frame on which a plurality of chips are mounted, and the mold has at least one chip corresponding to each chip. Equipped with multiple divisible cavity blocks with cavities of
This problem is solved by a resin sealing mold configured such that a gap variable means for varying the gap between the cavity blocks is provided in each gap between the cavity blocks.

[Function] As mentioned above, the conventional molding die used for manufacturing semiconductor devices has a plurality of molds corresponding to the plurality of chips mounted on one sheet of the lead frame. Instead of the cavity block being made up of a single cavity that cannot be separated, the present invention allows the cavity block to be divided into a plurality of cavity blocks each having at least one cavity.

A gap variable means is provided in the gap between each cavity block, so that the distance between each gap can be adjusted little by little.

In this way, the dimensions of the lead frame itself can be changed to match the deviation in the dimensions of the lead frame that occurs when it is heated in the mold due to the difference in the coefficient of thermal expansion of lead frames made of different materials. There is no need to create a new mold to accommodate the size difference.

Various methods can be used as the gap variable means, but a simple method is to use a tapered block or an eccentric cam whose two sides facing the gap are not parallel.

Thus, according to the present invention, for semiconductor devices having the same external shape, lead frames can be manufactured using the same mold even if the lead frames are made of different materials, and there is no need to change the mold depending on the material of the lead frame. disappears.

〔Example〕

FIG. 1 is a perspective view illustrating the invention in detail.

In the same figure, the mold l according to the present invention has a cavity block 5 that can be divided into eight pieces, with two cavities 4, which are provided facing each other from a runner 8 and have open gates 4, as a unit. It was constructed by

And in the gap between each cavity block 5,
A spring 61 that presses the taber block 61 and cavity block 5, whose two opposing surfaces are not parallel, against the fixed block 11.
A gap variable means 6 is provided.

This Taber block 61 was made of tool steel so as to have an inclination of 1/40 in the longitudinal direction, that is, so that the cavity block 5 would move by 50 μm when it advances 2IIlfll.

Then, when seven taber blocks 61 are inserted into the seven gaps between the eight cavity blocks 5 and pushed in, the gaps between the cavity blocks 5 widen, and when pulled out, they are pushed by the springs 62. The gap between cavity blocks 5 has been narrowed.

Further, a catch 12 is provided between the wall surface of the cavity block 5 and the sliding mold base 7 to prevent the cavity block 5 from coming off.

Further, a runner connecting groove 13 wider than the runner 8 is provided at a position where the Taber block 61 meets the runner 8 so that the runner 8 can be connected even if the Taber block 61 moves in the longitudinal direction.

One sheet of lead frame 3 has eight chips 2 mounted in it and has a length of 160 m, so if we compare the calculated values of mold 1 and lead frame 3, which have the same dimensions at room temperature, If the mold l is made of iron and the lead frame 3 is made of prepared alloy, the elongation will be about 0.13 mm too much, and if the lead frame 3 is made of iron-nickel alloy, it will be insufficiently elongated by 0.17 mm.

The dimensional deviation caused by the difference in coefficient of thermal expansion between the mold 1 and the two types of lead frames 3 was corrected by adjusting the degree of insertion of the seven Taper blocks 61.

On the other hand, this mold 1 is used as the lower mold, and the upper mold (not shown) that opposes it has the same specifications as mold 1 except that there is no runner connecting groove 13 in the taber block 61 since there is no runner 8. It becomes.

The thus assembled mold 1 and the opposed upper mold (not shown) were assembled into a mold base 7 in the same manner as a conventional cavity block as shown in FIG. 2, and a test mold was performed and evaluated.

As a result, it was confirmed that the adjustment using the Taber block 61 according to the present invention can sufficiently absorb the difference in thermal expansion coefficient for both lead frames 3.

In this case, a cavity block was created by dividing each cavity into two cavities connected to opposing gates, but the method of dividing the cavity block and the slope of the Taber plotter depend on the materials used for the mold and lead frame. Various modifications are possible in relation to the coefficient of thermal expansion.

Further, although a taper block is used as the gap variable means, for example, an eccentric cam may be appropriately provided between the cavity blocks to adjust the position.

(Effects of the Invention) As described above, according to the present invention, even if the material of the lead frame is changed, the position of the cavity block constituting the molding die can be adjusted.

By doing this, in order to compensate for dimensional deviations caused by the different coefficients of thermal expansion depending on the material of the lead frame,
There is no need to change the dimensions of the lead frame itself or the dimensions of the mold to match the respective coefficients of thermal expansion.

Therefore, the present invention greatly contributes to improving the efficiency of the resin sealing process by reducing mold replacement work and mold equipment costs.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating the present invention in detail, FIG. 2 is a perspective view illustrating a conventional molding die, and FIG. 3 is an enlarged view of the cavity in FIG. 2. In the figure, 1 is a mold, 2 is a chip, 3 is a lead frame, 4 is a cavity, 5 is a cavity block, and 6 is a gap variable means. I return 1 collar molded for I t9 Miya Ozuki Zuro 4 Toune Boku Seki '82 2nd f) "r Yaji Tipuro Tsuku no Sukusu 4a 3rd
figure

Claims (1)

[Claims] A lead frame (3) on which a plurality of chips (2) are mounted.
) for resin-sealing the mold (1), the mold (1)
is equipped with a plurality of divisible cavity blocks (5) each having at least one cavity (4) corresponding to each of the chips (2), and the cavity block (5) is provided in a gap between each of the cavity blocks (5). Gap variable means (
6) A mold for resin sealing, characterized in that it is provided with: