JPH01227462A - Lead frame - Google Patents

Abstract

PURPOSE:To reduce stress applied to a sealing resin and a die pad, and to load a large-sized semiconductor chip onto a resin seal type package 111 the same size as conventional packages by providing a slit to the die pad. CONSTITUTION:A lead frame has a die pad 2, to which slits 10 are formed, so that all cross sections of the arbitrary cross section in the direction of the long side, arbitrary surface in the direction of short side and diagonal cross section of a die pad 2 for the lead frame used for a resin seal type semiconductor package are crossed on at least one position of slits 10. The slits 10 are shaped so as to mutually run parallel up to the center at right angles with sides from one positions of each opposite side of the long sides and short sides of the end sections of the die pad 2. When there is the possibility of the lowering of the strength of the die pad 2 on die bonding and wire bonding by shaping the slits up to sections near the center from the end sections of the die pad 2, the slits 10 from the end sections of the die pad 2 are shortened, and slits 101 are formed insularly in the die pad 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lead frame for a resin-sealed package used in a semiconductor integrated circuit device.

BACKGROUND OF THE INVENTION As electronic devices become smaller and lighter, there is naturally a strong demand for smaller electronic components used in these devices. This electronic component is mounted on a printed circuit board and used.
However, recently, so-called surface mounting, which uses solder to adhere to both sides of a printed circuit board, has been adopted in order to further increase the packaging density.

Incidentally, a semiconductor integrated circuit device, which forms the core of this electronic component, often uses a resin-sealed semiconductor package.

The lead frame used for this is shown in Figure 3, and is a typical example of a resin-sealed package for surface mounting.
0utline “J” Lead Packa
ge) 1 is shown in FIG. 4 and will be explained with reference to these.

Figure 3 is a plan view of a lead frame used in a resin-sealed semiconductor package.The lead frame l is made of iron-nickel alloy or copper with a thickness of about 0.2 mm by pressing or chemical etching. be. This lead frame 1 includes a die pad 2 on which a semiconductor chip is placed, internal leads 3, external leads 4, tie bars 5, and hanging leads 6 that support the die pad 2. FIG. 4 shows a perspective view of an SOJ package using this lead frame. This SOJ package 8 has a lead frame with a semiconductor chip mounted on a die pad sealed with resin 7, and external leads 4 formed into a "J" shape.

Problems to be Solved by the Invention However, in recent years, semiconductor integrated circuit devices with a large number of elements, also called VLSIs, have been manufactured, and the size of a single semiconductor chip can reach up to 100 m1. Not rare. Moreover, these large semiconductor chips are housed in resin-sealed semiconductor packages of the same size as conventional ones in order to downsize devices.

However, in surface mounting, a semiconductor integrated circuit device is temporarily attached to a printed circuit board and bonded by a dip method in which it is passed through a solder bath, or a so-called reflow method in which soldering is performed by heating with infrared rays, but the temperature of this process is reaches a high temperature of about 240°C. As a result, cracks may occur in the sealing resin of the semiconductor integrated circuit device, causing serious quality problems. This is caused by stress due to the difference between the coefficient of thermal expansion of the sealing resin and the coefficient of thermal expansion of the encapsulated semiconductor chip or die pad. In particular, when a large semiconductor chip is encapsulated, the die pad on which it is placed also becomes thicker (which increases the stress applied to the encapsulating resin), and the thickness of the encapsulating resin that covers the die pad and semiconductor chip becomes thinner (which increases the stress applied to the encapsulating resin). This is because the stopper resin cannot mechanically resist stress caused by heat.

Means for Solving the Problem In order to solve this problem, the lead frame of the present invention has a die pad on which a semiconductor chip is mounted, with a cross section at any point in the long side direction and short side direction, or a cross section in the diagonal direction at least. , one place has a die pad formed across the slit.

According to the lead frame of the present invention, the slit formed in the die pad separates materials with different coefficients of thermal expansion, that is, the sealing resin and the die pad, so that they do not come into contact over a long distance, so that the maximum applied to the sealing resin is It is possible to reduce stress and to disperse stress. Also,
As the volume of the die pad decreases, the amount of resin increases, so the drag force of the resin increases.

Embodiment An embodiment of the lead frame of the present invention will be described with reference to the plan view of the die pad shown in FIG. This lead frame is made of iron-nickel alloy or copper with a thickness of about 0.2 m, and is formed from one point on each of the long and short sides of the end of the die pad 2 of the lead frame at right angles to the center. The slits 10 are provided so as to be parallel to each other. Note that the formation of slits from the sides is not limited to this, and the cross section at any point in the long side direction and short side direction of the die pad or the cross section in the diagonal direction is small (
It suffices if one of the holes is inserted across the slit 10. As a result, it is possible to prevent the die pad from coming into contact with sealing resins having different coefficients of thermal expansion over a wide range.

In addition, as another embodiment of the present invention, by inserting a slit from the end of the die pad 2 to the center, if there is a concern that the mechanical strength of the die pad 2 will decrease during die bonding or wire bonding, the second As shown in the figure, the slit IO at the end of the die pad 2 is short (so that the slit 101 is formed in the shape of an island in the die pad 2, and the slit 101 is formed in the shape of an island in the die pad 2, and the slit 101 is formed at an arbitrary point in the long side direction and the short side direction of the die pad 2. The cross section and the cross section in the diagonal direction are small (at least one cross section crosses the slits 10 and 101. The parts of the lead frame other than the die pad 2 are the same as those shown in FIG. 3).

Next, assembly of an SOJ package using the lead frame of the present invention will be explained. At this time, Figures 3 and 4
See also figure. After a semiconductor chip is fixed onto the die pad 2 using a resin called silver paste, for example, the bonding pads formed on the semiconductor chip and the internal leads 3 are connected using thin gold wires. Thereafter, the die pad 2 to which the semiconductor chip is fixed and the internal leads 3 are sealed with resin 7 using a sealing mold. At this time, the slit of the die pad is also filled with resin, and the contact between the die pad and the resin is severed. After this, the diameter 5 which connects the outer wire 4 is
After dropping the suspension leads 6, the external leads 4 are formed inward into a J" shape as shown in FIG. 4, and the SOJ package 8 is assembled.
is completed.

Effects of the Invention According to the lead frame of the present invention, the stress applied to the sealing resin and the die pad can be reduced by providing a slit in the die pad, so that a large semiconductor chip can be sealed with resin of the same size as before. It can be installed in a shaped package. As a result, it helps standardize processes and downsize equipment, and has great industrial value.

FIG. 3 is a plan view of a die pad for explaining the lead frame of the present invention used, FIG. 3 is a plan view of a conventional lead frame, and FIG. 4 is a perspective view of an SOJ which is a surface mounting semiconductor package.

2...Die pad, 10,101...
slit.

Name of agent: Patent attorney Toshio Nakao and one other person? ---Tiepad No. 1111

Claims (1)

[Claims] The slit is formed so as to cross at least one slit in any cross section in the long side direction, short side direction, and diagonal cross section of a die pad of a lead frame used in a resin-sealed semiconductor package. A lead frame with a die pad.