JPH0936298A - Lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the malfunction due to the stress in the case of more simply mounting a chip component such as a capacitor or a resistor. SOLUTION: The lead frame comprises extended parts 17, 20, 24, 26 extended in strip state so that the tip ends of the parts 17, 20 become electrode mounting parts 18, 21 for mounting the electrodes 4a, 4b of a capacitor chip 4. The tip ends of the parts 24, 26 become electrode mounting parts 25, 27 for mounting the electrodes 5a, 5b of a capacitor 5. Narrow width parts 22, 23, 28, 29 narrower than the widths of the parts 18, 21, 25, 27 are provided at the base end side from the parts 18, 21, 25, 27 of the parts 17, 20, 24, 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used when resin molding a chip component.

[0002]

2. Description of the Related Art In recent years, chip parts such as capacitors and resistors may be mounted in a resin-sealed semiconductor device in addition to a semiconductor chip. That is, as shown in FIG. 5, the lead frame 40 is formed with the first electrode mounting portion 41 and the second electrode mounting portion 42.
The electrode of the chip capacitor 43 is mounted on 42. At this time, the electrodes of the chip capacitor 43 are placed on both the electrode mounting portions 41 and 42 via the paste, and the temperature is raised to the curing temperature of the paste to be cured and returned to room temperature. In this process,
Since the chip capacitor 43 and the lead frame 40 (for example, copper) have different thermal expansion coefficients, thermal stress is generated at their joints. As a result, if the overall rigidity can cover the thermal stress, it can become residual stress, but if this force is not present in the weakest part (usually the paste bonded part), cracks may occur, or in some cases, It may be opened electrically.

A technique for avoiding this is disclosed in Japanese Patent Laid-Open No. 6-120.
No. 406 is disclosed. In this, the inner lead portion is provided with a groove or a step for relieving stress.
It is conceivable to provide a groove or a step in the electrode mounting portions 41, 42 using this technique.

[0004]

However, in order to obtain a structure having a groove or a step, a step for forming the groove and a bending process for forming the step are required, which increases the cost. The flatness of the entire lead frame may be deteriorated, which may lead to defective mounting of chip components and defective wire bonding.

Therefore, an object of the present invention is to provide a lead frame which can more easily avoid problems caused by stress when mounting chip parts such as capacitors and resistors.

[0006]

According to the first aspect of the invention, a strip-shaped extending portion is formed corresponding to the electrode of the chip component to be mounted, and the tip end side of the extending portion is the electrode. The gist of the lead frame is to provide an electrode mounting portion for mounting the electrode mounting portion and a narrow portion narrower than the width of the electrode mounting portion on the base end side of the electrode mounting portion in the extended portion.

A second aspect of the present invention has as its gist a lead frame in which the axis line of the narrow portion and the load acting line in the first aspect of the invention are offset from each other. The gist of the invention described in claim 3 is in the lead frame in which the axis of the narrow portion in the invention of claim 2 is arranged parallel to the load acting line and at a predetermined interval.

A fourth aspect of the invention has as its gist a lead frame in which the axis of the narrow portion in the second aspect of the invention is arranged so as to intersect the load acting line. A fifth aspect of the present invention has as its gist a lead frame arranged so that the axis of the narrow portion in the fourth aspect of the invention is orthogonal to the load acting line. (Operation) According to the invention described in claim 1, when a stress is applied between the electrode mounting portion and the chip component in the extended portion, the narrow portion is deformed to relieve the stress and the electrode is relieved. The occurrence of cracks and the like is avoided at the joint between the mounting portion and the chip component.

According to the second aspect of the present invention, the first aspect is provided.
In addition to the action of the invention described in (1), since the axis line of the narrow portion and the load acting line are offset, the lead frame is easily deformed in the spreading direction (the surface formed by the lead frame), and the electrode mounting portion and the chip component are Although a force is applied in the same direction at the joint portion of (1), it is difficult to deform in the direction (thickness direction of the lead frame) orthogonal to the spreading direction of the lead frame, and the force applied in this direction is weak. Therefore, peeling at the joint is suppressed.

According to the invention of claim 3, claim 2
In addition to the function of the invention described in (1), by making the axis of the narrow portion parallel to the load acting line and lengthening the interval, it becomes easier to deform in the spreading direction of the lead frame (the surface formed by the lead frame). .

According to the fourth aspect of the present invention, the second aspect is provided.
In addition to the function of the invention described in (1), by disposing the axis of the narrow portion so as to intersect the load acting line, the lead frame is easily deformed in the spreading direction (the surface formed by the lead frame).

According to the invention of claim 5, claim 4
In addition to the function of the invention described in (1), by arranging the axis of the narrow portion so as to be orthogonal to the load acting line, the most spreading direction of the lead frame (the surface formed by the lead frame)
It becomes easy to be transformed into.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a plan view of the lead frame, and more specifically, shows a state in which the IC chips 2, 3, chip capacitors 4, 5 and the like are mounted on the lead frame 1 made of a copper-based material. Where the chip capacitor 4
Has two back electrodes 4a and 4b, and the chip capacitor 5 has two back electrodes 5a and 5b.

In the island portion 6 of the lead frame 1,
The IC chips 2 and 3 are attached via a paste adhesive. The circuits formed on the IC chips 2 and 3 and the outer leads 7 and 8 are connected by bonding wires 9 and 10. Further, the circuits formed on the IC chips 2 and 3 and the outer leads 11, 12, and 13 are connected by bonding wires 14, 15, and 16 or the like.

The island portion 6 is also used as a ground ground, and a strip-shaped extending portion 17 extends from the island portion 6. The tip of the extended portion 17 serves as one electrode mounting portion 18 of the chip capacitor 4. A strip-shaped extending portion 20 extends from the inner lead 19 corresponding to the outer lead 11. The tip of the extended portion 20 serves as the other electrode mounting portion 21 of the chip capacitor 4. Both electrode mounting portions 18 and 21 are bonded and attached to the electrodes 4a and 4b of the chip capacitor 4 by paste or the like. In this way, the mounting portion 21 of the voltage application side electrode of the chip capacitor 4 is connected to the inner lead 19 and communicates with the outer lead 11. Further, a narrow width portion 22 is formed at the base end portion of the extension portion 17. Also, the extension 2
A narrow portion 23 is formed at the base end portion at 0.

A strip-shaped extending portion 2 extends from the island portion 6.
4 is extended. The tip of the extended portion 24 serves as one electrode mounting portion 25 of the chip capacitor 5. A strip-shaped extending portion 26 is formed on a part of the lead frame 1.
The tip of the extended portion 26 is the other electrode mounting portion 27 of the chip capacitor 5. Both the electrode mounting portions 25 and 27 are made of paste or the like to form the electrodes 5a and 5b of the chip capacitor 5.
It is installed by joining. Further, a narrow portion 28 is formed at the base end portion of the extended portion 24. Further, a narrow portion 29 is formed at the base end of the extended portion 26.

In such a lead frame 1, as shown in FIG.
A region 30 indicated by a chain double-dashed line indicates an outline when the resin is sealed. FIG. 1 shows an enlarged view of the lead frame 1 in the resin sealing region 30. Details of the extending portions 17, 20, 24, and 26 of the chip capacitors 4 and 5 in FIG. 1 will be described.

First, the extended portion 17 of the chip capacitor 4,
20 will be described. The chip capacitor 4 has a rectangular shape, and its longitudinal direction is the y-axis direction in FIG. The axis orthogonal to the y-axis direction in the paper surface direction of FIG. 1 is defined as the x-axis. Further, the axis orthogonal to the paper surface direction of FIG. 1 is the z axis. The narrow portion 2 of the extended portion 17 of the chip capacitor 4
2 extends in a direction parallel to the y-axis, and is displaced from the y-axis (y1) passing through the center of the chip capacitor 4 by a distance ΔL1. In addition, the width W1 of the narrow portion 22 is narrower than the width W2 at the base end portion of the extension portion 17, and the width W3 of the electrode mounting portion 18 is set.
It is smaller than that (W1 <W2, W1 <W3).

The narrow portion 23 of the extended portion 20 of the chip capacitor 4 extends in the x-axis direction. The width W4 of the narrow portion 23 is smaller than the width W5 of the inner lead 19 and smaller than the width W6 of the electrode mounting portion 21 (W
4 <W5, W4 <W6).

The narrow portion 29 of the extended portion 26 of the chip capacitor 5 extends in a direction parallel to the y-axis, and the distance ΔL2 is from the y-axis (y2) passing through the center of the chip capacitor 5.
Only the difference. The width W9 of the narrow portion 29 is smaller than the width W10 of the electrode mounting portion 27 (W9 <W1.
0).

Further, in the extended portion 24 of the chip capacitor 5, the narrow portion 28 extends in the x-axis direction. The width W7 of the narrow portion 28 is smaller than the width W8 of the electrode mounting portion 25 (W7 <W8).

Next, the process of actually mounting the chip capacitors 4 and 5 on the lead frame 1 will be described in detail. First, apply paste or the like on the lead frame 1,
Equipped with chip capacitors 4 and 5.

Then, the temperature is raised to the curing temperature of the paste by equipment such as a high temperature constant temperature bath, a hot plate, or a belt furnace, and is held for a predetermined time. After the curing is completed, the temperature is returned to room temperature.

At this time, there is almost no stress between the chip capacitor mounting portions before the paste is hardened. However, when the curing is completed and when the temperature is returned to room temperature, thermal stress is generated due to the difference between the thermal contraction force of the paste material and the thermal expansion coefficient of the respective materials of the chip capacitor and the lead frame.

At this time, if the thermal stress generated is T, and the bending strength in the narrow portions 22, 23, 28, 29 of the lead frame 1 in the x and y directions (the surface direction of the lead frame 1) is F, When the relation of T> F ... (1) is established, the narrow portions 22, 23, 2
8 and 29 are bent and deformed.

On the other hand, T is T = f1 (α1, α2, E1, E2, δ) (2) α1; of the chip capacitor, from the material properties of the chip capacitors 4 and 5 and the lead frame 1 and the curing temperature of the paste. Thermal expansion coefficient α2; thermal expansion coefficient of lead frame E1; Young's modulus of chip capacitor E2; Young's modulus of lead frame δ; temperature difference between paste curing temperature and room temperature.

Further, F is from the material properties of the lead frame and the shape of the narrow portion F = f2 (E2, w, t) (3) w; width of the narrow portion t; thickness of the narrow portion Can be expressed as

Therefore, the width w of the narrow portion is determined by determining the material property values (α1, α2, E1, E2) of each portion, the paste curing condition (δ), and the lead frame thickness t.
It is obtained from the equations (1), (2), and (3), and the relaxation design for the thermal stress becomes possible.

Here, as the material of the lead frame, 42
The comparison between the case of using alloy and the case of using copper-based material is mentioned. That is, in recent years, a copper-based material having good thermal conductivity has been widely used as a material for the lead frame, and the coefficient of thermal expansion is higher than that of the 42 alloy which has been the mainstream in the past. Specific values are 17 to 19 ppm / ° C for copper type and 7 ppm / ° C for 42 alloy.
It is. On the other hand, chip capacitors and the like are often made of ceramics, and the coefficient of thermal expansion thereof is about 10 ppm / ° C. Therefore, the copper-based lead frame is more likely to be subjected to thermal stress than the 42-alloy lead frame, which is a severe condition.

After mounting the chip capacitors 4 and 5 on the lead frame 1 in this manner, wire bonding is performed and then resin molding is performed. Furthermore, FIG.
At, the tie bar portion 31 in the outer leads 7, 8, 11, 12, 13 is cut. In this way, a MCP (Multi Chip Package) semiconductor device in which a plurality of chips are mounted on the lead frame and which is resin-molded is completed.

Next, the deformation direction when a stress such as a thermal stress is applied will be described. In FIG. 1, when the above-mentioned thermal stress is applied, the chip capacitors 4 and 5 tend to deform in the longitudinal direction (y-axis direction). On the other hand, the narrow portion 23,
The reference numeral 28 extends in a direction orthogonal to the deformation direction and has a narrow width, so that the rigidity in the y-axis direction is small. Therefore, the presence of the narrow portions 23 and 28 facilitates displacement of the electrode mounting portions 21 and 25 in the y-axis direction.

The narrow portions 22 and 29 extend in the direction parallel to the y-axis, and the extending direction is the chip capacitors 4 and 4.
It is deviated from the y-axis passing through the center of 5 and has a narrow width. Therefore, the rigidity in the y-axis direction is small. Therefore, the presence of the narrow portions 22 and 29 facilitates displacement of the electrode mounting portions 18 and 27 in the y-axis direction.

That is, with respect to the y-axis passing through the center of the chip capacitor 4 (shown as y1 in FIG. 1), the narrow portions 22, 2
3 is asymmetric, and the electrode mounting portions 18 and 21 are easily displaced in the y-axis direction when thermal stress is applied. Similarly,
The narrow portions 28 and 29 are asymmetric with respect to the y-axis passing through the center of the chip capacitor 5 (shown as y2 in FIG. 1), and when thermal stress is applied, the electrode mounting portions 25 and 27 are y
Easy to displace in the axial direction. By allowing such deformation not in the z-axis direction but in the x- and y-directions, peeling of the joint portion can be prevented when the paste is cured, and the strength of the joint portion can be considered to be sufficient. At the time of wire bonding, it is possible to secure the flatness of the entire lead frame, improve the mountability of chip components, and reliably perform wire bonding.

In other words, in FIG. 1, the angle formed by the y-axis (y1) passing through the center of the chip capacitor 4 and the extending direction of the narrow portion 23 is θ1, and the y-axis passing through the center of the chip capacitor 5 (y2). ΔL1 = 0, θ1 = 0, and Δ, where θ2 is the angle between the extension direction of the narrow portion 28 and the extending direction of the narrow portion 28.
When L2 = 0 and θ2 = 0, the narrow portions 22, 23, 28 and 29 are symmetrical with respect to the y1 axis and the y2 axis. this is,
This corresponds to a case where the first extension portion and the second extension portion of the lead frame are extended on the y1 axis as shown in FIG. 3, and the chip capacitor is mounted on the tip end portion thereof with a paste. When the environmental temperature at this time changes, stress is generated between the lead frame (17 to 19 ppm / ° C) made of the copper-based material and the chip capacitor (10 ppm / ° C) made of the ceramic material, and the stress is placed on the y1 axis. The first extension part and the second extension part are deformed in the z-axis direction by "buckling", and the lead frame is deformed in the z-axis direction. In the present example shown in FIG. 1, this is intentionally avoided, and a deviation ΔL1 is generated in the y axis with respect to the y1 axis (and the y2 axis) which is the load acting line.
(ΔL2) is provided or the angle θ1 (θ2) is provided to make the narrow portions 22, 23 (28, 29) asymmetrical, and the narrow portions 22, 23 (28, 29) are formed on the line of the y1 axis (and the y2 axis). Two
The device is designed so that the axis of 9) is not located.

As described above, in the lead frame 1, the electrode mounting portion 1 is located closer to the base end than the electrode mounting portions 18, 21, 25, 27 in the extending portions 17, 20, 24, 26.
Narrow portion 22,2 narrower than the width of 8,21,25,27
Since 3, 28, 29 are provided, the extension portions 17, 20, 2
When stress is applied between the electrode mounting portions 18, 21, 25, 27 of the chip capacitors 4, 5, and the chip capacitors 4, 5, the narrow portions 22, 23, 28, 29 are deformed and the chip capacitors 4, 5 of the chip capacitors 4, 5 are deformed. It is possible to suppress the occurrence of defects such as cracks at the joint.

Further, in FIG. 2, the outer leads 7, 8, 1
Even when the tie bar portions 31 of the cables 1, 12, 13 are cut after being resin-molded, the stress tries to propagate from the outer leads 11, 12 to the chip capacitors 4, 5, but the narrow portions 23, 28 provided in the middle of the propagation paths. Are absorbed by the chip capacitors 4 and 5 and the chip capacitors 4 and 5 are protected without applying unreasonable stress to the chip capacitors 4 and 5.

Further, the load acting lines (y1 and y2 in FIG. 1) extending linearly with the axes of the narrow portions 22, 23 (28, 29).
Since they are offset, the lead frame 1 is easily deformed in the spreading direction (the surface formed by the lead frame 1), and is not easily deformed in the direction orthogonal to the spreading direction of the lead frame 1 (the thickness direction of the lead frame 1). Therefore, peeling of the joint portion can be prevented, deterioration of the flatness of the lead frame 1 can be avoided, and mountability of chip components and connectivity of wire bonding can be secured.

In particular, in the narrow portions 22 and 29, their axes are parallel to the load acting line and the intervals ΔL1 and ΔL.
By making 2 longer, the lead frame 1 is more likely to be deformed in the spreading direction. In the narrow portions 23 and 28, their axes intersect the load acting line (θ1 ≠
By arranging such that 0, θ2 ≠ 0), the lead frame 1 can be easily deformed in the spreading direction, and the axes of the narrow portions 23 and 28 are orthogonal to the load acting line (θ.
1 = 90 °, θ2 = 90 °), the lead frame 1 can be most easily deformed in the spreading direction.

Although the chip capacitor has been described as the chip component in the above description, the present invention can be applied to the case where a chip resistor, a chip coil, a chip oscillator or the like is mounted.

Further, in FIG. 1, the narrow portions 22, 23, 2
8 and 29 have been described as extending in a predetermined length direction, the width is locally narrowed by providing the V-shaped notch 32 in the strip-shaped extension 26 as shown in FIG. The narrowed portion 33 may be provided. In FIG. 4,
A case where a narrow portion 33 is provided instead of the narrow portion 29 in FIG. 1 is shown.

[0041]

As described above in detail, according to the invention described in claim 1, it is possible to more easily avoid the problem caused by stress when mounting chip parts such as capacitors and resistors. Demonstrate.

According to the invention described in claim 2, according to claim 1
In addition to the effect of the invention described in (1), peeling at the joint can be suppressed. According to the invention of claim 3, in addition to the effect of the invention of claim 2, the lead frame can be further easily deformed in the spreading direction.

According to the invention set forth in claim 4, according to claim 2,
In addition to the effect of the invention described in (1), the lead frame can be easily deformed in the spreading direction. According to the invention of claim 5, in addition to the effect of the invention of claim 4, it can be most easily deformed in the spreading direction of the lead frame.

[Brief description of drawings]

FIG. 1 is a partially enlarged view of a lead frame according to an embodiment.

FIG. 2 is a plan view of the lead frame according to the embodiment.

FIG. 3 is a diagram for explaining a lead frame in the embodiment.

FIG. 4 is a plan view of a lead frame according to another embodiment.

FIG. 5 is a plan view of a lead frame for explaining a conventional technique.

[Explanation of symbols]

4, 5 ... Chip capacitors, 4a, 4b, 5a, 5b ...
Electrodes, 17, 20, 24, 26 ... Extensions, 18, 21,
25, 27 ... Electrode mounting portion, 22, 23, 28, 29 ... Narrow portion

Claims (5)

[Claims] 1. An extension part extending in a strip shape corresponding to an electrode of a chip component to be mounted is formed, and a tip end side of the extension part is used as an electrode mounting part for mounting the electrode, and the extension part is provided. A lead frame characterized in that a narrow portion narrower than the width of the electrode mounting portion is provided on the base end side of the electrode mounting portion in the portion. 2. The lead frame according to claim 1, wherein the axis line of the narrow portion and the load acting line are offset from each other. 3. The lead frame according to claim 2, wherein the axis of the narrow portion is arranged parallel to the load acting line and at a predetermined interval. 4. The lead frame according to claim 2, wherein the axis of the narrow portion is arranged so as to intersect the load acting line. 5. The lead frame according to claim 4, wherein an axis of the narrow portion is arranged so as to be orthogonal to a load acting line.