JP2839641B2 - Lead frame for ceramic package - Google Patents

Description

The present invention relates to a lead frame for a ceramic package used as an external terminal when a semiconductor chip is hermetically sealed in a ceramic package. .

(Prior Art) In a semiconductor device, each electrode pad provided on a semiconductor chip generally has a different vertical and horizontal arrangement depending on a design method or the like, and a pitch between adjacent electrodes in an arrangement along a length direction. There was variation in the pitch between adjacent electrodes in the array along the width direction. After designing the semiconductor chip, a ceramic package is designed using a lead frame corresponding to the arrangement position of each electrode pad on the semiconductor chip as an external terminal, and the semiconductor chip is hermetically sealed with this package. That was generally done.

For this reason, the lead frame used as the external terminal is generally configured as shown in FIG. 3 and FIG.

That is, for example, a glass-sealed ceramic package is
It is constructed by printing and melting a low melting point glass on the surface of a ceramic substrate and fixing a lead frame 2 'to the surface. As described below, each electrode pad of a semiconductor chip mounted on this package is formed as follows. In order to correspond to the position, the interval P ₁ ′ of the gap formed between the inner leads 2 ′ a, 2 a ′ along the length direction of the lead frame 2 ′ and the inner leads 2 b ′, 2b ′
Interval P ₂ which is formed between 'between some extent although were such that a uniform, in particular inner lead 2'a at four corners, spacing P ₃ formed between 2'b' is considerably wider Had become.

Then, a semiconductor chip (not shown) is fixed to a cavity 3 formed substantially at the center of the ceramic substrate 1 via a mount paste, and the respective inner leads 2'a, 2'b of the lead frame 2 'are connected to the semiconductor chip. After electrically connecting each electrode pad with a bonding wire such as an Al wire, a cap (not shown) is covered, and the upper and lower glasses are melted through a furnace at about 450 ° C. Was hermetically sealed.

Here, when the semiconductor chip housed in the package is hermetically sealed by applying heat to melt the upper and lower glass as described above, gas is generated from the mount paste fixing the semiconductor chip, As a countermeasure against the generated gas, it has been generally practiced to use a mount paste itself.

(Problems to be Solved by the Invention) However, as the size of the semiconductor chip increases and the number of pins increases, the package size increases, and the amount of mount paste for fixing the semiconductor chip tends to increase. Therefore, the pressure of the gas generated from the mount paste also gradually increases. When the pressure of the gas generated inside the package when airtightly sealed by applying heat is increased, the gas is increased in the widest place, that is, the inner leads 2'a and 2 'at the four corners in particular. b
Attempts to flow out of the gap P ₃ ′ between the gaps, and the glass located there will cause poor sealing, impairing uniform sealing, etc., and have a serious problem that productivity and yield will decrease. It has become.

That is, in a conventional general ceramic package, it has become increasingly difficult to treat sealing failures due to the influence of gas generated by the mount paste with the mount paste itself as the size of the ceramic paste increases.

In view of the above, an object of the present invention is to provide a lead frame which is improved by improving the lead frame itself, thereby preventing a defective seal caused by gas and improving productivity and yield.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, a lead frame for a ceramic package according to the present invention is used as an external terminal when a semiconductor chip is hermetically sealed in a rectangular ceramic package. In the lead frame for a ceramic package, the intervals between the tips of the adjacent inner leads of the lead frame are substantially equal over the entire circumference.

(Operation) According to the present invention having the above configuration, when the semiconductor chip is mounted and covered with a cap, and then heated and hermetically sealed by applying heat, the gas generated from the mount paste is supplied to each of the inner leads adjacent to each other on the lead frame. Will try to flow evenly through each equally spaced gap formed between them,
As a result, it is possible to prevent the gas pressure in a part of the gap formed between the inner leads from being increased by the lead frame itself, and to prevent poor sealing between the ceramic substrate and the cap.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. 1 and FIG.

This figure shows a glass packaged ceramic package (Cerdip type package) similar to the above conventional example.
This is an example in which a low melting glass is printed on the surface of a ceramic substrate 1 and melted, and a lead frame 2 is fixed to the surface.

The lead frame 2 has a gap P between the inner leads 2a, 2a along the length direction.
_1, the inner leads 2b along the widthwise direction, and the interval P ₂ formed between 2b equals (P ₁ = P ₂₎ as, each inner lead 2a further located at the four corners, formed between 2b Interval P
_{3 is} also configured to be equal to the intervals P ₁ and P ₂ (P ₁ = P ₂ = P ₃ ). That is, one of the inner leads 2a located along the length direction and located at the end or the inner leads 2b located along the width direction and located at the end (in the figure, along the width direction). While increasing the width of the inner lead 2b) located and located at the end,
By extending in the other direction, no gap is formed in this corner.

That is, the gap between the inner leads at a relatively wide corner, which generally occurs in the related art, is closed by the inner leads 2a or 2b of the lead frame 2 so that the gap does not occur.

Then, a semiconductor chip (not shown) is fixed to a cavity 3 formed substantially at the center of the ceramic substrate 1 via a mounting paste, and each inner lead 2a, 2b of the lead frame 2 and each electrode pad of the semiconductor chip are connected. After electrically connecting with a bonding wire such as an Al wire, a cap (not shown) is covered, and the upper and lower glasses are melted through a furnace at about 450 ° C. to hermetically seal to form a semiconductor device. is there.

When the semiconductor chip is mounted and covered with a cap and then heated and hermetically sealed, gas is generated from the mount paste. The gas is generated by the inner leads 2a, 2a, 2b, and 2b adjacent to each other on the lead frame 2. and 2a, so attempts to uniformly flowing out from the equal gaps _{P 1, P 2, P 3} (P 1 = P 2 = P 3) formed between 2b. As a result, the force that causes the gas to flow out is evenly distributed, and the inner lead
2a, 2a, 2b, 2b and a part of the gap formed between 2a, 2b are prevented from increasing in gas pressure by the lead frame 2 to prevent poor sealing between the ceramic substrate 1 and the cap. can do.

Although the above embodiment shows an example in which the present invention is used for a glass-sealed ceramic DIP type package, it can be used for a ceramic package in which sealing failure due to gas is concerned, including general glass-sealed ceramic packages. Of course.

〔The invention's effect〕

Since the present invention is configured as described above, when the semiconductor package housed in the ceramic package is hermetically sealed by applying heat to the ceramic package, the bias of the force that tends to flow out the gas generated from the mount paste, It is possible to prevent the occurrence of defective sealing between the ceramic substrate and the cap by being prevented by the lead frame, thereby improving the productivity and the yield.

In addition, there is an effect that the semiconductor device can be configured using the same process as that of the conventional ceramic package as it is.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a plan view showing a state in which a lead frame is arranged on a ceramic substrate. FIG. 2 is an enlarged view of a part II in FIG. 3 is a diagram corresponding to FIG. 1 showing a conventional example, and FIG. 4 is an enlarged view of a part IV in FIG. 1. Ceramic substrate 2. Lead frame 2a, 2b
...... Inner lead, 3 ... Cavity.

Continuation of the front page (56) References JP-A-1-150345 (JP, A) JP-A-58-131632 (JP, U) JP-A-62-42254 (JP, U) JP-A-63-5251 (JP) , Y2) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 23/50 H01L 23/053-23/057

Claims (1)

(57) [Claims] 1. A lead frame for a ceramic package which is used as an external terminal when a semiconductor chip is hermetically sealed in a rectangular ceramic package, between a tip portion of each inner lead adjacent to the lead frame. A lead frame for a ceramic package, wherein the intervals are substantially equal over the entire circumference.