Resin sealing type semiconductor device and method of manufacturing the same, and lead frame

Abstract

The invention is directed to firm bonding between semiconductor dies etc bonded to a lead frame and wire-bonding portions of the lead frame by ultrasonic Al wire bonding, and the prevention of shortcircuit between the semiconductor dies etc due to a remaining portion of the outer frame of the lead frame after the outer frame is cut. By extending the wire-bonding portion etc on the lead frame in a wire-bonding direction and connecting the wire-bonding portion etc to the outer frame of the lead frame through a connection lead etc, the ultrasonic vibration force in the ultrasonic Al wire bonding is prevented from dispersing and the Al wire and the wire-bonding portion etc are firmly bonded. The outer frame is cut after a resin sealing process is completed. Even when a portion of the outer frame remains on the side surface of the resin package, connection between the connection lead etc and other hanging lead etc are prevented by providing a notch etc in the outer frame between the connection lead etc and the hanging lead etc.

Claims

1. A semiconductor device, the device comprising: a lead frame comprising: an internal region; two or more leads extending from the internal region; an outer frame surrounding the internal region, wherein the outer frame comprises a first edge facing the internal region and a second edge facing the internal region; first and second connection portions connecting the internal region of the lead frame to the outer frame; and a notch formed in an edge of the outer frame that is closest to the internal region and between the first and second connection portions, wherein the notch is formed in a region of the outer frame that is spaced apart from each region of the outer frame that is connected to the connection portions, wherein the first edge of the outer frame extends from a region of the outer frame connected to the first connection portion to the region of the outer frame where the notch is formed, and wherein the second edge of the outer frame extends from a region of the outer frame connected to the second connection portion to the region of the outer frame where the notch is formed; a semiconductor die that is die-bonded to the internal region of the lead frame; and a resin package sealing the semiconductor die and a portion of the lead frame, wherein the outer frame of the lead frame is exposed from the resin package.

2. The device of claim 1, wherein the internal region comprises two or more islands.

3. The device of claim 1, wherein a resin burr is formed in the notch.

4. The device of claim 1, wherein the semiconductor die is wire-bonded to the lead frame.

5. The device of claim 4, wherein the lead frame comprises at least one connection portion extending in a first direction so as to connect a portion of the lead frame that is wire-bonded to the outer frame and at least one connection portion extending in a second direction so as to connect the portion of the lead frame that is wire-bonded to the outer frame, wherein the first direction is different than the second direction.

6. The device of claim 5, wherein the first direction is substantially perpendicular to the second direction.

7. The device of claim 4, wherein the semiconductor die is wire-bonded to the lead frame by applying ultrasonic energy.

8. The device of claim 1, wherein two or more semiconductor dies are die-bonded to different portions of the internal region of the lead frame.

9. The device of claim 1, wherein the first and second connecting portions each connect different islands in the internal region to the outer frame.

10. A method of processing the device of claim 1, the method comprising cutting the lead frame through at least the notch to remove the outer frame of the lead frame.

11. A semiconductor device, the semiconductor device comprising: a lead frame comprising: an internal region; two or more leads extending from the internal region; a peripheral region; and a first connection portion connecting the internal region of the lead frame to a first portion the peripheral region of the lead frame; a second connection portion connecting the internal region of the lead frame to a second portion the peripheral region of the lead frame; and an opening in the peripheral region of the lead frame, wherein the opening electrically insulates the first connection portion from the second connection portion; a semiconductor die that is die-bonded to the internal region of the lead frame; and a resin package sealing the semiconductor die and a portion of the lead frame, wherein the peripheral region of the lead frame is exposed from the resin package, wherein the opening is spaced apart from portions of the peripheral region connected to the first connection portion and the second connection portion, wherein a third portion of the peripheral region comprises an edge that faces the resin package, wherein the edge of the third portion of the peripheral region extends from the first portion of the peripheral region to the opening, wherein a fourth portion of the peripheral region comprises an edge that faces the resin package, and wherein the edge of the fourth portion of the peripheral region extends from the second portion of the peripheral region to the opening.

12. The device of claim 11, wherein the opening in the peripheral region of the lead frame is formed by cutting through a notch in the lead frame.

13. The device of claim 11, wherein a resin burr is formed in the opening in the lead frame.

14. The device of claim 11, wherein the semiconductor die is wire-bonded to the lead frame.

15. The device of claim 14, wherein the lead frame comprises at least one connection portion extending in a first direction so as to connect a portion of the lead frame that is wire-bonded to the outer frame and at least one connection portion extending in a second direction so as to connect the portion of the lead frame that is wire-bonded to the outer frame, wherein the first direction is different than the second direction.

16. The device of claim 14, wherein the semiconductor die is wire-bonded to the lead frame by applying ultrasonic energy.

17. The device of claim 11, wherein two or more semiconductor dies are die-bonded to different portions of the internal region of the lead frame.

18. The device of claim 11, wherein the first connection portion connects to a first island in the internal region to the lead frame and the second connection portion connects to a second island in the internal region of the lead frame.

19. The device of claim 14, wherein the semiconductor die is wire-bonded to the lead frame by applying ultrasonic energy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view showing a method of manufacturing a resin sealing semiconductor device before it is resin-sealed in a first embodiment of the invention.

(2) FIG. 2 is a plan view showing a method of manufacturing a resin sealing semiconductor device before it is resin-sealed in a second embodiment of the invention.

(3) FIG. 3 is a plan view showing a method of manufacturing a resin sealing semiconductor device before it is resin-sealed in a conventional embodiment.

(4) FIG. 4 is a view showing a lead frame where a semiconductor die etc are mounted, that is set in molds of a resin sealing apparatus.

(5) FIG. 5 is a perspective view of the lead frame where the semiconductor die etc are mounted, that is set in the molds of the resin sealing apparatus, from the upper mold side.

DETAILED DESCRIPTION OF THE INVENTION

(6) A first embodiment of the invention will be described hereafter referring to figures.

(7) Although there are some types of lead frame 1 for use in which a plurality of same patterns is arrayed in a single row, in two rows or in three rows, the description will be given by showing one of the patterns in detail since the invention is understood by describing one pattern. The description will be given using a simple package of an SIP (Single In-line Package) type as a package.

(8) Before the description of the embodiment, the structure of the lead frame 1 for realizing the invention will be described referring to FIG. 3. On the lead frame 1, islands 13 where a power semiconductor die 2 and a controller semiconductor die 3 are mounted, and an island 13 and inner leads 1b where other die capacitor 4 etc are mounted are connected to an outer frame 8 of the lead frame through hanging leads 5a, 5b and 5c, respectively, as shown in FIG. 3, thereby enhancing the stiffness of these. When an Au wire for thermocompression bonding is employed as a wire for wire-bonding the semiconductor die 3 and wire-bonding portions 14a, 14b and 14c of the lead frame 1, the wire-bonding force is mainly applied in the vertical direction to the main surface of the lead frame 1. Therefore, the force applied in the leftward, rightward, upward and downward directions in the main surface of the lead frame 1 shown in FIG. 3 is weak, and thus a problem does not often occur in this structure of the lead frame 1. However, when Al wires 6a, 6b, 7a, 7b and 7c are employed to perform ultrasonic wire-bonding, the intensive force by the ultrasonic vibration is applied in the leftward, rightward, upward and downward directions in the main surface of the lead frame 1, and thus a problem is likely to occur.

(9) Hereafter, the first embodiment of the invention will be described referring to FIG. 1.

(10) First, the lead frame 1 is provided, the power semiconductor die 2 having high current flow and a large heat value is die-bonded to the predetermined island 13 of the lead frame 1 using a solder preform or the like. The lead frame 1 used in this case is made of a Cu member on which Ni etc is plated. The controller semiconductor die 3 is die-bonded to the predetermined island 13 using Ag paste or the like since it has low power consumption. A passive element such as the die capacitor 4 is also bonded to the island 13 and the inner lead 1b of the lead frame 1 using Ag paste. When Ag paste is used for the bonding, Ag is plated on the lead frame 1, too.

(11) Then, ultrasonic wire-bonding is performed between the power semiconductor die 2 and the controller semiconductor die 3 and between the controller semiconductor die 3 and the wire-bonding portion 14a on the lead frame 1 using thick Al wires 6a and 6b, thereby forming a power source line. Simultaneously, ultrasonic wire-bonding is performed between the controller semiconductor die 3 and the gate of the power semiconductor die 2 and between the controller semiconductor die 3 and the wire-bonding portions 14b and 14c on the lead frame 1 through slightly thinner Al wires 7a, 7b and 7c.

(12) It is a concept of the first embodiment of the invention to counter the force applied in the leftward, rightward, upward and downward directions of the lead frame 1 in the ultrasonic bonding using these Al wires so as to effectively use the ultrasonic vibration as wire-bonding force. For example, the ultrasonic vibration direction when the thick Al wire 6b is wire-bonded to the wire-bonding portion 14a on the lead frame 1 will be considered. In this case, the ultrasonic vibration for the Al wire 6b is in the extending direction of the Al wire 6b for the wire-bonding, i.e., a left upward oblique direction in FIG. 1. In this case, the force of the ultrasonic vibration includes upward force and leftward force in the figure. With the hanging lead 5a only, as shown in FIG. 3, since the leftward force is not countered by any seaport structure, the wire-bonding portion 14a on the lead frame 1 is vibrated in the left direction even slightly and thus the ultrasonic force is not used effectively.

(13) On the other hand, in FIG. 1 showing the invention, a connection lead 9 is provided to firmly support the left side of the wire-bonding portion 14a on the lead frame 1, thereby preventing the ultrasonic vibration force from escaping to the left side. Since the connection lead 9 is connected to the stiff outer frame 8 of the lead frame 1, it further prevents the ultrasonic vibration force from escaping to the left side. Also in the ultrasonic vibration force in the right downward oblique direction for bonding the Al wire 6b to the pad electrode on the controller semiconductor die 3, similarly, the downward force is countered by the hanging leads 5a and the rightward force is countered by the connection lead 9, thereby realizing firm bonding.

(14) Also in the ultrasonic vibration force in the left upward oblique direction for bonding the Al wire 6a to the pad electrode on the controller semiconductor die 3, similarly, the upward force is countered by the hanging leads 5a and the leftward force is countered by the connection lead 9. Next, the ultrasonic vibration force applied to the pad electrode on the power semiconductor die 2 will be considered. In this case, the ultrasonic vibration force is in the extending direction of the Al wire 6a, i.e., in the right downward oblique direction in FIG. 1. The ultrasonic vibration force in this case includes downward force and rightward force. The downward force is countered by the outer leads 1a. Although the rightward force is not countered in the case of FIG. 3, a connection lead 10 is provided and formed integrally with the outer frame 8 in FIG. 1 of the invention and thus the rightward force is countered enough.

(15) The vibration force for the ultrasonic wire-bonding of the slightly thinner Al wire 7a etc is also countered by the connection lead 9 etc in the similar manner to the thick Al wire 6a etc. In the case of the Al wire 7a, although the left upward force is applied to a portion of the inner lead 1b for the wire bonding, the force is weaker than the Al wire 6a etc and thus the upward force and leftward force are countered by the hanging lead 5c. In the case of the Al wire 7b, the force is mainly applied in the upward and downward directions, the upward force is countered by the hanging leads 5a and the downward force is countered by the outer leads 1a. In the case of the Al wire 7c, the vibration force is applied in the leftward and rightward directions, the force is firmly countered by the connection leads 9 and 10.

(16) As described above, since the ultrasonic vibration force is firmly countered and thus contained by the connection leads 9 and 10 employed in the first embodiment as well as the hanging leads 5a, 5b and 5c and the outer leads 1a, stable bonding is achieved even by ultrasonic Al wire bonding to realize wire-bonding with high reliability. Then, the lead frame 1 where the power semiconductor die 2 etc are mounted is resin-sealed in a resin sealing process, and a portion surrounded by a dashed and dotted line in FIG. 1 becomes a resin package 12 filled with resin. Then, the tie bars 11 that support the outer leads 1a and the outer frame 8 of the lead frame 1 that support the whole lead frame 1 until the resin sealing process is completed are cut, and according to needs, and a bending process etc are performed to the outer leads 1a, thereby completing a resin sealing type semiconductor device.

(17) Before the description of a second embodiment, the contents and problems of the resin sealing process and the process of cutting the outer frame 8 of the lead frame 1 will be examined. In the resin sealing process, as shown in FIG. 4, the lead frame 1 where the semiconductor die 2 etc that are wire-bonded through the Al wire 6a etc are mounted is held between an upper mold 100 and a lower mold 101 of a resin sealing apparatus, and resin is injected therein. In FIG. 4, the tie bars 11 on the left side are held between the upper mold 100 and the lower mold 101, and serves as dam bars to prevent the resin from flowing to the outside of the resin package 12 from the left side. On the right side, the outer frame 8 of the lead frame 1 is held between the upper mold 100 and the lower mold 101, and prevents the resin from flowing to the outside of the resin package 12 from the right side. On the front and rear sides, similarly, the outer frame 8 prevents resin from flowing to the outside of the resin package 12.

(18) In this case, in order to form the resin package 12 as small as possible, the hanging leads 5a etc shown in FIG. 4 that merely support the island 13 etc and have no other function are formed as thin and short as possible. Furthermore, the resin package 12 is formed so that the inner portion 8a of the outer frame 8 of the lead frame 1 shown in FIG. 2 and the circumference of the resin package 12 are in contact with each other as shown in FIG. 4. When the resin sealing process is completed, the tie bars 11 and the outer frame 8 that complete the function as a supporting body are cut simultaneously. However, sometimes the outer frame 8 may be not completely removed and a portion of the outer frame 8 may remain on the circumference of the resin package 12 depending on the positional relation etc between the outer side of the resin package 12 and the inner side of the outer frame 8 of the lead frame 1.

(19) In this case, the hanging leads 5a etc are connected to the remaining and unnecessary portion of the outer frame 8, and thus become a supporting body for the remaining portion. In particular, since the connection lead 9 etc described above that also function as a kind of hanging leads are formed to have a much larger width than the usual hanging leads 5a etc in order to counter the intensive ultrasonic vibration force in the Al wire bonding, these support the remaining unnecessary portion of the outer frame 8 more widely and firmly than the hanging leads 5a etc. In detail, in FIG. 1 showing the first embodiment, when the outer frame 8 of the lead frame 1 is cut, since the outer frame 8 extends from the end of the resin package 12 to the outside of the resin package 12, it is difficult to cut the outer frame 8 completely, and the outer frame 8 of the lead frame 1 is much likely to remain thin on the lateral and upper side surfaces of the resin package 12.

(20) If this is not removed by some method, in the case of FIG. 1, a problem occurs such that the hanging lead 5b connected to the island 13 where the semiconductor die 2 is mounted and the hanging lead 5a connected to the island 13 where the semiconductor die 3 is mounted remain connected through the remaining portion of the outer frame 8 of the lead frame 1 on the side surface of the resin package 12 and are not separated. The same problem also occurs to the connection lead 9 having a much larger width than the hanging lead 5a etc, that is provided in order to effectively use the ultrasonic vibration force in the Al wire bonding. In detail, the connection lead 9 connected to the island 13 where the semiconductor die 3 is mounted and the hanging lead 5c connected to the inner lead 1b to which one of the electrodes of the die capacitor 4 is bonded remain connected through the remaining portion of the outer frame 8 of the lead frame 1 on the side surface of the resin package 12 and are not separated.

(21) In order to prevent or eliminate these problems, the hanging lead 5a etc are formed longer to expose a portion of the hanging lead 5a etc to the outside of the resin package 12, and in this state the exposed portion is cut together with the outer frame 8, or according to needs, the remaining portion of the outer frame 8 is scraped down from the circumference of the resin package after it is cut. It is noted that the portion of the outer frame 8 that is widely connected to the wide connection lead 9 etc is not easily scraped down. Furthermore, in order to form the hanging lead 5a etc longer so as to expose a portion of these to the outside of the resin package 12, a change is needed such that the lead frame 1 is formed larger as a whole by the elongated amount of the hanging lead 5a etc, or the width of the outer frame 8 is narrowed by that amount so as not to change the whole size of the lead frame 1.

(22) Hereafter, the second embodiment of the invention will be described in detail referring to FIG. 2. This embodiment prevents the connection between the connection lead 9 etc and the hanging lead 5c etc due to an unnecessary remaining portion of the outer frame 8 of the lead frame 1 and prevents short circuit between the semiconductor devices etc due to a remaining portion of the outer frame 8, without a need for the change in the size of the lead frame 1 and the scraping of the remaining portion of the outer frame 8.

(23) FIG. 5 is a perspective view of the resin sealing apparatus shown in FIG. 4 from the upper mold 100 side, showing a structure of the lead frame 1 where the semiconductor device 2 etc are mounted. On the outer leads 1a side, the tie bars 11 are firmly held between the upper mold 100 and the lower mold 101 to serve as dam bars and prevent resin from flowing to the outer lead 1a side. On both the lateral sides and the upper side of the resin package 12, similarly, the outer frame 8 of the lead frame 1 firmly held between the upper mold 100 and the lower mold 101 prevents resin from flowing to the outside of the resin package 12.

(24) In the outer frame 8 of the lead frame 1 held between the upper mold 100 and the lower mold 101, that is in contact with the end of the resin package 12, notches 15 and 16 are formed from the inside toward the outside of the outer frame 8.

(25) In the second embodiment of the invention, by forming the notches 15 and 16 etc in the outer frame 8 of the lead frame 1, as shown in FIGS. 5 and 2, a portion of the outer frame 8 of the lead frame 1 remaining on the side surface of the resin package 12 is separated and the hanging lead 5c etc and the connection lead 9 etc are not connected to prevent shortcircuit between the semiconductor device 2 etc. The notches 15 etc are formed small on the side of the outer frame 8 of the lead frame 1, that abuts the resin package 12 as shown in FIG. 2, and have size such that those has no influence on the total strength of the lead frame 1. The width is such that a remaining portion of the outer frame 8 of the lead frame 1 is separated. The length is such that the end is exposed from the resin package 12. Although FIG. 2 shows the two notches 15 and 16 only, these are formed between the hanging leads including the connection leads that need to be separated.

(26) The forming of the notch 15 etc in the outer frame 8 of the lead frame 1 also has an advantage that the notch 15 etc are used as alignment marks when the lead frame 1 is held between the upper mold 100 and the lower mold 101 in the resin sealing process and thus the inner side of the outer frame 8 of the lead frame 1 and the mold 100 etc are aligned with high accuracy. The notch 15 etc are concaved from the inner side toward the outer side of the outer frame 8, and thus resin burrs 18 are formed in the concaves in the similar manner to the resin burrs 17 formed between the tie bars 11 on the outer leads 1a and the resin package 12, as shown in FIG. 5.

(27) Therefore, when the outer frame 8 is cut next, since the outer frame 8 is cut almost at the boundary between the outer frame 8 and the resin package 12 by targeting the black resin burrs 18 inside the notch 15 etc, the occurrence probability of the remaining outer frame 8 becomes low. Furthermore, since the outer frame 8 of the lead frame 1 is cut across the notch 15 etc, even if a portion of the outer frame 8 of the lead frame 1 remains on the side surface of the resin package 12, the remaining portion of the outer frame 8 is separated at the notch 15 etc. In detail, even when a portion of the outer frame 8 of the lead frame 1 remains, the notch 15 etc realizes the separation of the remaining portion of the outer frame 8.

(28) Therefore, the existence of the notch 15 prevents the connection between the hanging lead 5a and the connection lead 9 that extend from the island 13 where the controller semiconductor die 3 is mounted and the hanging lead 5c that extend from the inner lead 1b where one of the electrodes of the die capacitor 4 is mounted. Similarly, the existence of the notch 16 prevents the connection between the hanging lead 5a extending from the island 13 where the controller semiconductor die 3 and the die capacitor 4 are mounted and the hanging lead 5b extending from the island 13 where the power semiconductor die 2 is mounted due to a remaining portion of the outer frame 8 of the lead frame 1.

(29) As a result, the second embodiment of the invention prevents shortcircuit between the semiconductor dies etc due to a remaining portion of the outer frame 8 of the lead frame 1 after the cutting of the outer frame 8, and realizes the manufacture of a resin sealing type semiconductor device with high reliability. Although the notch 15 etc are formed in a U shape in FIG. 2, other different shapes than the U shape, such as a V shape or a semicircle shape extending from the inner side toward the outer side of the outer frame 8, are possible as long as the object of the invention is achieved.

(30) Furthermore, although an Al wire is used as an ultrasonic wire-bonding member in the description of the embodiments of the invention, the invention is also applicable to a case of using a wire with a copper base. As for the package, an SIP type package is used for the description, but the invention is also applicable to other package such as a DIP (Dual In-line Package) type package etc as long as the concept of the invention is unchanged.

(31) Even when the wire-bonding between the pad electrode of the semiconductor die 3 etc, and the wire-bonding portion 14a etc on the lead frame 1 or the pad electrode of the semiconductor die 2 are performed using an Al wire 6a etc by ultrasonic wire-bonding, firm bonding is achieved. Furthermore, even when a portion of the outer frame 8 of the lead frame 1 remains on the circumference of the resin package 12, shortcircuit is prevented between the semiconductor die 2 etc sealed in the resin package 12.