LEADFRAME-BASED SEMICONDUCTOR PACKAGE HAVING ARCHED BEND IN A SUPPORTING BAR AND LEADFRAME FOR THE PACKAGE
A leadframe-based semiconductor package and a leadframe for the package are revealed. The semiconductor package primarily includes parts of the leadframe including one or more first leads, one or more second leads, and a supporting bar disposed between the first leads and the second leads and further includes a chip attached to the first leads, the second leads and the supporting bar, a plurality of bonding wires and an encapsulant. The supporting bar has an extended portion projecting from the first bonding finger and the second bonding finger and connected to a non-lead side of the encapsulant wherein the extended portion has an arched bend to absorb the pulling stresses and to block stress transmission. Cracks caused by delamination of the supporting bar will not be created during trimming the supporting bar along the non-lead side of the encapsulant. Moisture penetration along the cracks of the supporting bar to the die- bonding plane under the chip is desirably prevented.
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The present invention relates to semiconductor packages, especially to leadframe-based semiconductor packages and leadframes for semiconductor packages.
BACKGROUND OF THE INVENTIONEven though printed circuit boards and other substrates have gradually replaced leadframes as chip carriers of semiconductor packages, however, leadframe-based semiconductor packages still have the advantages of lower cost and high reliability. One of the leadframe-based semiconductor packages is Chip-On-Lead (COL) semiconductor package. The backside of semiconductor chip is disposed on a plurality of leads of a leadframe. Then the chip is electrically connected to the fingers of the leads by a plurality of bonding wires formed by wire bonding. Finally, an encapsulant is formed by molding to encapsulate the chip and the bonding wires where the external leads of the leads exposed and extended from the sides of the encapsulant are used as the external electrical connections. Even though COL semiconductor packages are very mature packages, however, there are still some molding defeats.
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The main purpose of the present invention is to provide a leadframe-based semiconductor package and a leadframe for the semiconductor package. The leadframe has a supporting bar disposed between the two symmetric leads to increase the carrying strengths for a chip to avoid tilting or shifting of a chip during molding processes and to eliminate broken bonding wires and exposed internal leads from the encapsulant.
The second purpose of the present invention is to provide a leadframe-based semiconductor package and a leadframe for the semiconductor package. The leadframe has a supporting bar with an arched bend as a stress-stopping point to avoid pulling stresses directly deliver to the die-bonding plane under the chip during trimming the supporting bar along the sides of an encapsulant. Moisture will not penetrate along cracks of the supporting bar into the die-bonding plane under the chip leading to delamination issues.
The third purpose of the present invention is to provide a leadframe-based semiconductor package and a leadframe for the semiconductor package. The leadframe has symmetric leads to increase carrying strengths for a chip without affecting the layout of the leads.
The fourth purpose of the present invention is to provide a leadframe-based semiconductor package and a leadframe for the semiconductor package to enhance the locking functions of the supporting bar inside an encapsulant.
According to the present invention, a leadframe-based semiconductor package is revealed, primarily comprising one or more first leads, one or more second leads, a supporting bar, a chip, a plurality of bonding wires, and an encapsulant. Each first lead has a first bonding finger and each second lead has a second bonding finger. The supporting bar is disposed between the first leads and the second leads. The chip is attached to the first leads, the second leads and the supporting bar where the chip has a plurality of bonding pads. The bonding wires are electrically bonded the bonding pads to the first bonding fingers and to the second bonding fingers. The encapsulant encapsulates parts of the first leads including the first bonding fingers, parts of the second leads including the second bonding fingers, the supporting bar, the chip, and the bonding wires. Moreover, the supporting bar has an extended portion projecting from the first bonding fingers and the second bonding fingers and connecting to a non-lead side of the encapsulant. The extended portion has an arched bend.
Please refer to the attached drawings, the present invention is described by means of embodiments below.
According to the preferred embodiment of the present invention, a leadframe-based semiconductor package and a leadframe for the package are revealed. As shown in
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To be summarized, the arched bend 232 of the supporting bar 230 encapsulated by the encapsulant 260 and formed between the first leads 210 and the second leads 220 can avoid the shifting or tilting of the chip 240 during molding processes and can be used as a pulling-stress stop point for the supporting bar 230 to avoid moisture penetrating through the cracks along the supporting bar 230 leading to delamination. Moreover, the pull-stress stop point will not affect the layout of the leads nor the wire bonding processes.
The above description of embodiments of this invention is intended to be illustrative and not limiting. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure.
Claims
1. A leadframe-based semiconductor package primarily comprising:
- one or more first leads having a first bonding finger;
- one or more second leads having a second bonding finger;
- a supporting bar disposed between the first leads and the second leads;
- a chip disposed on the first leads, the second leads, and the supporting bar, the chip having a plurality of bonding pads;
- a plurality of bonding wires electrically connecting the bonding pads to the first bonding finger and to the second bonding finger; and
- an encapsulant encapsulating parts of the first leads including the first bonding finger, parts of the second leads including the second bonding finger, the supporting bar, the chip, and the bonding wires;
- wherein the supporting bar has an extended portion projecting from the first bonding finger and the second bonding finger and connecting to a non-lead side of the encapsulant;
- wherein the extended portion has an arched bend.
2. The leadframe-based semiconductor package of claim 1, wherein the encapsulant encapsulates the space enclosed by the arched bend.
3. The leadframe-based semiconductor package of claim 1, wherein the width of the arched bend is not smaller than the width of a portion of the supporting bar between the first bonding finger and the second bonding finger.
4. The leadframe-based semiconductor package of claim 1, wherein the encapsulant has a first lead side and the second lead side being parallel to each other and connected with both ends of the non-lead side; wherein the first leads further have a plurality of first external leads exposed and extended from the first lead side; wherein the second leads further have a plurality of second external leads exposed and extended from the second lead side; wherein the first bonding finger and the second bonding finger are adjacent to but not connecting to the non-lead side of the encapsulant.
5. The leadframe-based semiconductor package of claim 4, wherein the first leads and the second leads are symmetric with respect to the supporting bar.
6. The leadframe-based semiconductor package of claim 1, wherein the portions of the first leads, the portions of the second leads, and the portion of the supporting bar attached by the chip are formed on a die-bonding plane, wherein the arched bend has a half-circular profile extruded from the die-bonding plane.
7. The leadframe-based semiconductor package of claim 6, wherein the chip has an active surface and a back surface, and the bonding pads are disposed on the active surface; wherein the back surface is attached to the first leads, the second leads, and the supporting bar such that the first bonding finger, the second bonding finger and the arched bend are located between the chip and the non-lead side of the encapsulant.
8. The leadframe-based semiconductor package of claim 7, wherein each of the first and second bonding fingers has a free end toward the non-lead side; wherein the free ends are completely encapsulated by the encapsulant.
9. A leadframe for a leadframe-based semiconductor package, primarily comprising:
- one or more first leads having a first bonding finger;
- one or more second leads having a second bonding finger;
- a supporting bar disposed between the first leads and the second leads;
- wherein the supporting bar has an extended portion projecting from the first bonding finger and the second bonding finger and extending to a non-lead side of an encapsulation area;
- wherein the extended portion has an arched bend.
10. The leadframe of claim 9, wherein the width of the arched bend is not smaller than the width of a portion of the supporting bar between the first bonding finger and the second bonding finger.
11. The leadframe of claim 9, wherein the encapsulation area has a first lead side and a second lead side being parallel to each other and connected with both ends of the non-lead side; wherein the first leads further have a plurality of first external leads extended from the first lead side; wherein the second leads further have a plurality of second external leads extended from the second lead side; wherein the first bonding finger and the second bonding finger are adjacent to but not extending to the non-lead side of the encapsulation area.
12. The leadframe of claim 1, wherein the first leads and the second leads are symmetric with respect to the supporting bar.
13. The leadframe of claim 9, wherein the portions of the first leads, the portions of the second leads, and the portion of the supporting bar are formed on a die-bonding plane; wherein the arched bend has a half-circular profile extruded from the plane.
14. The leadframe of claim 13, wherein each of the first and second bonding fingers has a free end toward the non-lead side; wherein the free ends are located within the encapsulation area.
Type: Application
Filed: Jun 5, 2008
Publication Date: Dec 10, 2009
Applicant:
Inventors: Chin-Fa Wang (Hsinchu), Wan-Jung Hsieh (Hsinchu), Yu-Mei Hsu (Hsinchu)
Application Number: 12/133,898
International Classification: H01L 23/495 (20060101);