JPS6217382B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mounting structure of an integrated circuit device such as a resin molded small electronic component such as a consumer IC or a linear IC.

Resin molded packages are commonly used as packages for small-signal ICs such as consumer ICs and linear ICs due to their low manufacturing costs.

Here, a method for manufacturing an IC in a resin mold package, which has been commonly used in the past, and its manufacturing will be explained with reference to FIGS. 1 and 2.

Dual in-line lead frames are used to assemble resin molded semiconductor devices, which are patterned thin metal plates made of iron-based materials such as iron-cobalt-nickel alloys by precision pressing or etching. This lead frame is made up of components as shown in FIG. That is, an outer frame 1 that is the frame of the lead, a tab 3 consisting of a small piece to which the circuit element 2 is attached located at the center of the outer frame 1, a thin tab lead 4 that connects this tab 3 to the outer frame 1, and an outer frame 1. It consists of a plurality of leads 5 extending from the inside of each side of the frame 1 toward the tab 3, and a dam 6 consisting of a thin connecting piece that connects these leads 5 and prevents the resin from flowing out during molding. When assembling the semiconductor device, after fixing the circuit element 2 on the tab 3, each electrode of the circuit element 2 and the tip of the corresponding lead 5 are connected with a thin wire 7, and then, The inside of the chain line frame surrounded by the dam 6 is molded with resin, the leads 5 are cut and separated from the outer frame 1, and the unnecessary dam 6 is cut and removed. Further, the tab lead 4 is cut and removed at the base of the mold part 8 made of resin (where a cross-cut break 4a is applied) (FIG. 2 shows the finished product).

On the other hand, due to the demand for miniaturization of devices into which electronic components are installed, the miniaturization of such packages is progressing.
For example, a linear IC with 28 leads (external terminals) that used to be 40 mm long, 13 mm wide, and 4 mm high is now being considered to be 10 mm long, 10 mm wide, and 2 mm high.

On the other hand, high-density packaging is progressing in linear ICs, and there is a demand for smaller package outlines, and small-signal ICs such as linear ICs are also becoming more highly integrated. I C
However, it is becoming necessary to give sufficient consideration to the heat dissipation effect, but miniaturization is extremely difficult with the above-mentioned approach.

In other words, even though packages have been miniaturized as described above, the total surface area of the package has been drastically reduced (for example, it has been reduced to 1/5 in the previous example). It is becoming difficult to hire
It was necessary to change to a ceramic package structure, which is complicated to assemble but has good heat dissipation, or to adopt a conventional large package structure.
Currently, it is difficult to miniaturize small-signal ICs that generate a relatively large amount of heat.

Therefore, an object of the present invention is to provide electronic components such as small-signal ICs that generate a large amount of heat at low cost, are compact, and have good thermal characteristics. .

In order to achieve such an object, an embodiment of the present invention has a tab lead that supports a circuit element, that is, a tab on which an integrated circuit pellet is attached, protrudes outside the sealing body, and its tip is made of a material having high thermal conductivity, for example. The present invention is connected to a wiring board such as a ceramic board or fixed to a heat sink, and the present invention will be explained below with reference to Examples.

FIG. 3 shows an IC (semiconductor device) according to an embodiment of the present invention. In the figure, 9 is a tab lead connected to the tab 10, 11 is an IC chip that is a circuit element mounted on the tab 10, 12 is a lead, and 13 is a connection between the inner end of the lead 12 and the external electrode of the circuit element 11. It is a connecting wire. Also, lead 12
The tab 10, the circuit element 11, the wire 13, and the inner end of the lead, except for the outer end thereof, are entirely covered with a molded part (sealing body) 14 made of resin. Further, each lead 12 is bent in the same direction as shown in FIGS. 4a and 4b, and its tip is bent again to form a flat joint end 15. Furthermore, the tab lead 9 also has its outer end protruding from the mold part 14. Note that the outer end of the tab lead in FIG. 3 extends straight from the side surface of the molded portion 14 in the lateral direction. In addition, the mold part 14
The inner tab lead 9 extends in a direction perpendicular to the side surface of the mold part 14 so that the distance from the mold edge to the tab 10 is the shortest.

Next, the mounting structure of the IC will be explained with reference to FIGS. 4a and 4b. FIG. 1A shows a state in which the IC 16 is attached to a ceramic substrate 17, and the outer ends of the leads 12 are fixed to a wiring layer (not shown) of the ceramic substrate 17 via solder (not shown). Further, when attaching to a substrate 17 having good thermal conductivity such as ceramic, the outer end of the tab lead 9 is bent downward and the tab lead 9 is bent downward.
It is fixed to via solder (not shown).

In addition, as shown in FIG. It is bent above the molded part 14 and fixed to a heat sink 19 having good thermal conductivity (for example, a plate made of copper, aluminum, etc. or a heat sink fin) via solder (not shown).

In this way, the outer end of the tab lead 9 that supports the circuit element 11 that is a heat source is connected to the ceramic substrate 17 and the heat sink 19 that serve as heat sinks with high thermal conductivity, so that heat is transferred through the tab lead 9. The heat is radiated sequentially from the heat sink. Furthermore, since the length (path) of the tab lead is short, the heat transfer path is also short and the heat dissipation effect is high. This mounting structure, that is, this embodiment in which two tab leads are fixed to the ceramic plate, has a much lower thermal resistance than the case where the tab leads do not contact the ceramic plate (see FIG. 7). In other words, the thermal resistance of the package itself is, for example, 216°C/W, partly because the mold part has become smaller.
However, when attached to a mounting board with good thermal conductivity such as a ceramic board, a small package has a lower thermal resistance than a large package. In this case, the lead frame is made of copper. Note that it is clear from the graph in Figure 7 that a substrate with low thermal conductivity such as glass epoxy cannot be used due to its large thermal resistance, so Figure 4b
It is necessary to fix the tab lead to a heat sink made of copper or the like, as shown in the figure below.

Therefore, if this example is used, the heat dissipation characteristics will be good even if the package (mold part) is downsized to 10 mm or less, so it is suitable for consumer ICs, linear ICs, etc. that generate relatively heat. It becomes possible to downsize.

Note that the present invention is not limited to the above embodiments. Furthermore, if a material with high thermal conductivity such as copper is used for the lead frame, the heat dissipation effect will be further increased.

Furthermore, as shown in FIG. 5, if a structure is adopted in which the outer ends of the leads 12 and tab leads 9 are brought into direct contact with the ceramic substrate 17 and fixed with solder 20, the mounting area becomes narrower. In addition, the distance l from the outer edge of the mold part 14 to the bending part of the lead 12 and tab lead 9 is made as short as possible,
By reducing the height H of the leads 12 and tab leads 9, the heat transfer path is also shortened, and the heat dissipation characteristics are further improved.

Moreover, as shown in FIGS. 6a and 6b, the mold part 1
Wider the tab lead 9 protruding from 4,
As shown in FIGS. 6c and 6d, the heat transfer (heat radiation) effect may be increased by increasing the number of tab leads 9.

As described above, according to the present invention, even a small signal IC that generates a relatively large amount of heat can be miniaturized.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of assembling an IC using a conventional lead frame, Fig. 2 is a front view of the IC, Fig. 3 is a plan view of an IC according to an embodiment of the present invention, and Figs. 4 a and b. 5 is a partially sectional front view showing another mounting structure, and FIGS. 6 a to 6 d are plan views showing a part of a lead frame used in an embodiment of the present invention. FIG. 7 is a graph showing the relationship between substrate thermal conductivity and thermal resistance. 9...Tab lead, 10...Tab, 11...Circuit element, 12...Lead, 13...Wire, 14...Mold part, 15...Joining end, 16...IC, 17...Ceramic board, 18...Printed circuit board, 19...Radiation plate,
20...Solder.

Claims (1)

[Claims] 1 (a) A tab, a pair of leads connected to the tab and extending in opposite directions, and a group of other leads with one end extending in the vicinity of the tab and the other end extending in four directions. (b) a chip fixed on the tab; (c) a substantially square lead member that seals the chip, the tab, the lead connected to the tab, and a portion of a plurality of other lead groups; A mounting structure when an electronic component is mounted on a wiring board, the electronic component having a resin sealing body and having a part of the lead connected to the tab located outside the resin sealing body, The tips of the connected leads are bent in the opposite direction to the lead tips of the plurality of other lead groups and connected to the heat sink, and the lead tips of the plurality of other lead groups are connected to the conductor layer provided on the wiring board. Mounting structure of connected electronic components.