JP2765476B2 - Lead frame design method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a lead frame, and more particularly to a method for designing a lead frame used when designing the lead frame by restricting the width and interval of the lead frame to a certain value or more.

[0002]

2. Description of the Related Art A conventional lead frame designing method will be described with reference to the drawings. FIG.
FIG. 4 is a flowchart showing a conventional lead frame designing method proposed in the lead arrangement design system of Japanese Patent Application Laid-Open No. 71963. FIG. 4 shows a design using the conventional lead frame designing method shown in the flowchart of FIG. It is a figure which shows the example of a lead frame arrangement | positioning. Hereinafter, the conventional lead frame designing method will be described with reference to the flowchart of FIG. 3 and the lead frame arrangement example of FIG.

In the conventional lead frame designing method shown in FIG. 3, a lead frame arrangement is designed by the following operation steps.

[0004] First, in operation step S ₃₁ includes a chip outline 22, cavity line 2 indicating an offset amount required for bonding of the lead frame
3 and an offset line 24 parallel to one side of the chip outer shape 22 facing the cavity line 23.
, Package outline 25, and design conditions of the number n of lead frames (positive integer).

[0005] Then, in the operation step S _32, the cavity line 23 and the offset line 24, and the package outline 25 corresponding to the number of lead frames n and (2n-1) is divided into pieces (FIG. 4 In the conventional example, n = 2 is shown), and straight lines 26, 27, 28 and 29 connecting the corresponding dividing points on the cavity line 23 and the offset line 24 are created, and the offset line 24 and the package outer shape are formed. Straight lines 30, 31, 32, and 33 connecting the corresponding division points on the line 25 are formed, and the portions delimited by these straight lines are alternately used as lead frame portions 34, 35 and gap portions 36 thereof. Create 35.

[0006] Next, in operation step S _33, to measure the width and spacing of the lead frame portion in the bending points 37, 38 and 39, 40 on the lead frame, whether the distance is appropriate for the design condition Is evaluated, and if it is not appropriate as a design condition, a position separated by a predetermined constant value on a straight line or an extension line direction of the offset line 24 is calculated, and the position on the lead frame portion corresponding thereto is calculated. Move the inflection point. Lead frame part 3 in FIG.
In 5, the minimum width at the inflection points 39 and 40 is calculated by the distance from the inflection point 40 to a point 41 perpendicular to the straight line 32. If the calculated distance is not appropriate as a design condition, the offset is calculated. Calculate a point 42 separated by a predetermined distance in the direction of the extension of the line 24,
The position of the bending point is moved from the bending point 40 to the position of the point 41 to correct the width of the lead frame portion.

[0007] In operation step S ₃₄ calculates the bonding position of the leadframe portion 34, 35 is defined as a design condition in the operation step S _35, in the operation step S _35, the lead frame portions 34 and 35,
And evaluate whether it is appropriate to said calculated in operation step S ₃₄ defined bonding location design conditions, where appropriate proceeds to action step S _36, if not suitable operation steps S ₃₃ Then, the operation steps after the operation step S33 are repeatedly executed. Then, in the operation step _S36 , the created lead frame is displayed.

As described above, the above-mentioned Japanese Patent Application Laid-Open No.
In the conventional lead frame designing method proposed in the lead arrangement design system of JP-A-63, design work is performed by trial and error.

[0009]

In the above-described conventional lead frame designing method, the designing operation is performed by trial and error, and the width of the lead frame portion at the bonding position is affected by the bonding design conditions. This is not necessarily constant, and thus has a disadvantage that there is a surface lacking in stability when bonding the semiconductor chip and the lead frame portion, and a disadvantage that the strength of the lead frame portion is deteriorated. There is.

[0010]

According to a lead frame designing method of the present invention, there is provided a lead frame designing method for arranging and configuring a lead frame on a semiconductor chip, wherein an outer shape of the semiconductor chip and an offset amount for bonding the lead frame are provided. A first operation step of inputting design conditions including a cavity line indicating the following, an offset line corresponding to the cavity line, a package outer shape, and a lead frame number n (positive integer); The package outer shape is defined as (2
n-1), and a straight line connecting the corresponding dividing points on the cavity line and the offset line is created, and a straight line connecting the corresponding dividing points on the offset line and the package outer shape. A second operation step of tentatively creating a lead frame by alternately arranging portions divided by these straight lines as gaps between the lead frame and the lead frame portion; A third operation step of calculating the bonding position of each lead frame created in the second operation step; and setting a first bending point on the side surface of each lead frame as viewed from the center of the semiconductor chip. With reference to the design conditions including the width and spacing of the wires and the bonding position conditions for each lead frame, Until each of the lead frames has a predetermined width and interval, the operation of moving the bending point to a predetermined distance on a straight line or an extension line constituting the bending point is repeated. And a fourth operation step of correcting the side surface of each of the lead frames.

The fourth operation step includes:
Measure the width and interval of each lead frame at the bending point on each lead frame created in the second operation step, and evaluate whether these widths and intervals are suitable for the design conditions. If the design conditions are not appropriate, calculate a position separated by a predetermined constant value on a straight line of the offset line or an extension of the offset line, and calculate the bending point on the lead frame corresponding to the predetermined value. A fifth operation step of moving to the calculated position and correcting the width of the lead frame at the refraction point; and each of the lead frames is suitable for each bonding position design condition calculated in the third operation step. Evaluate whether or not there is, and if appropriate, proceed to the next seventh operation step; otherwise, return to the fifth operation step. In the sixth operation step, when the respective lead frames are suitable for the respective bonding position design conditions calculated in the third operation step, the respective lead frames created are displayed. And a seventh operation step.

[0012]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a flowchart showing a lead frame designing method according to an embodiment of the present invention. FIG. 2 is a flowchart showing the design using the lead frame designing method according to the present embodiment shown in the flowchart of FIG. It is a figure which shows the example of a lead frame arrangement | positioning. Hereinafter, the lead frame designing method of the present embodiment will be described with reference to the flowchart of FIG. 1 and the lead frame arrangement example of FIG.

In the lead frame designing method of this embodiment shown in FIG. 1, the layout of the lead frame is designed by the following operation steps.

[0015] First, the operation in step S _11, the chip outline 1 inputs the cavity line 2 indicating an offset amount for bonding the lead frame portion in the semiconductor chip, cavity line 2 facing the chip outline The design conditions of the offset line 3 parallel to one side, the package outer shape 4 and the number n of lead frames are input (this embodiment shows a case where n = 2).

[0016] Then, in operation step S ₁₂ includes a cavity line 2, the offset line 3, a package outline 4 for the number leadframe n (2n-
1) Divide into pieces (n = 2 in this embodiment), and create straight lines 5 to 8 connecting the corresponding division points on the cavity line 2 and the offset line 3 to obtain the offset line 3 and the package outer shape. 4, create straight lines 9 to 12 connecting the corresponding division points, and define the portions separated by these straight lines as
The lead frame portions 13 and 14 and the gap portion 15 are alternately formed, so that the lead frame portions 13 and 14
Create

[0017] In operation step S _13, the operation steps S to calculate the bonding position of the lead frame portions 13 and 14 defined as a design condition at _15, in the operation step S _14, the bending point 16 on the lead frame,
The width and interval of the lead frame portion at 17 and 18 and 19 are measured, and it is evaluated whether or not the distance is appropriate for the design condition. Alternatively, a position separated by a predetermined constant value in the direction of the extension is calculated, and the bending point on the lead frame portion is moved correspondingly. FIG.
In the lead frame portion 14, the bending point 1
The minimum widths at 8 and 19 are calculated from the distance from the bending point 19 to a point 20 perpendicular to the straight line 11. If the calculated distance is not appropriate as a design condition, the minimum width is predetermined on the straight line 8. Is calculated, the position of the bending point is moved from the bending point 19 to the position of the point 21, and the width of the lead frame portion at the bending point is corrected.

[0018] In operation step S _15, when the lead frame 13 and 14, to assess whether it is appropriate for the operation is calculated in step S ₁₃ defined bonding location design conditions, it is suitable proceeds to operation steps S _16, if not appropriate returns to operation steps S _14, executes repeatedly the operation steps of the operation steps S ₁₄ and subsequent to. And in the end to the operation step S _16, and displays the read frame created on a predetermined display screen.

[0019]

As described above, according to the present invention, the first bending point on the lead frame as viewed from the center of the chip is formed on the side surface of the lead frame bonded to the semiconductor chip by forming the lead frame. By arranging the lead frame at a predetermined distance in a straight line or in the extending direction, the width and interval of the lead frame at the bonding position can always be set to constant values. There is an effect that the stability at the time of bonding can be increased and the strength of the lead frame can be maintained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing operation steps of one embodiment of the present invention.

FIG. 2 is a view showing an arrangement of a lead frame created by using the embodiment shown in FIG. 1;

FIG. 3 is a flowchart showing operation steps of a conventional lead frame designing method.

FIG. 4 is a diagram showing an arrangement of a lead frame created by using the conventional method shown in the above 3;

[Explanation of symbols]

 1,22 Chip outline 2,23 Cavity line 3,24 Offset line 5-12,26-33 Straight line 13,14,34,35 Lead frame part 15,36 Lead frame gap part 16-19,37-40 Bending point 20, 21, 41, 42 points

Claims (2)

(57) [Claims] 1. A lead frame designing method for arranging and configuring a lead frame on a semiconductor chip, comprising: a cavity line indicating an outer shape of the semiconductor chip, an offset amount for bonding the lead frame, and a cavity line corresponding to the cavity line. A first operation step of inputting design conditions including an offset line, a package outline, and a lead frame number n (positive integer); and setting the cavity line, the offset line, and the package outline with respect to the lead frame number n. Each is divided into (2n-1) pieces, a straight line connecting the corresponding division points on the cavity line and the offset line is created, and the corresponding division points on the offset line and the package outer shape are connected. To create these straight lines A second operation step of tentatively creating a lead frame by alternately arranging portions separated by straight lines as gaps between the lead frame and the lead frame portion; A third operation step of calculating a bonding position of each lead frame; and a design including, on a side surface of each of the lead frames, setting an initial bending point as viewed from the center of the semiconductor chip and including a width and an interval of each lead frame. With reference to the conditions and the bonding position conditions of each lead frame, a width and an interval of a predetermined size, until the respective lead frames come to have, on a straight line or an extension line direction constituting the bending point. The operation of moving the bending point to a predetermined constant distance is repeatedly performed to correct the side surface of each of the lead frames. 4. A lead frame designing method, comprising: at least a fourth operation step. 2. The fourth operation step measures the width and interval of each lead frame at a bending point on each lead frame created in the second operation step, and the width and the interval are measured. Evaluate whether it is suitable for the design conditions, if not appropriate as the design conditions, calculate a position separated by a predetermined constant value on the straight line of the offset line or in the direction of its extension, A fifth operation step of moving the bending point on the lead frame corresponding to this to the calculated position and correcting the width at the refraction point of the lead frame; and wherein each of the lead frames is in the third operation step Whether the calculated bonding position design condition is appropriate or not is evaluated.
The sixth operation step, and if not appropriate, returning to the fifth operation step; and in the sixth operation step, each of the lead frames is calculated in the third operation step. 7. The lead frame designing method according to claim 1, further comprising: a seventh operation step of displaying each created lead frame when appropriate for each bonding position design condition.