Lead frame
By designing a structure with a flattening direction and a proportional width of the processing area on the metal protective pad of the lead frame, the problem of incorrect contact shapes and sizes during the etching process of the lead frame is solved, and the correct connection and efficient use of electronic packages are achieved.
Patent Information
- Application Number
- CN202421066682.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Priority Date
- 2024-05-09
- Filing Date
- 2024-05-16
- Publication Date
- 2025-01-14
- Estimated Expiration
- 2034-05-16
AI Technical Summary
During the etching process of existing wire frames, the etching rate along the protective layer forming direction is slow, resulting in incorrect shape and size of the contact, incorrect positioning and connection, resulting in poor contact or inability to conduct.
Design a lead frame whose metal protective pad is flattened along the forming direction, and the width of the processing area in the perpendicular forming direction is greater than the width in the parallel forming direction to ensure that the shape and size of the contacts after etching comply with the design.
Through this design, errors in contact shape and size caused by different etching rates are avoided, ensuring that electronic packages can be connected correctly when used and avoiding problems such as poor contact.
Smart Images
Figure CN222355135U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a semiconductor device, and more particularly to a lead frame for a semiconductor element. Background Art
[0002] Today's electronic products are becoming thinner and smaller, but the number of semiconductor input / output (I / O) points used in them has increased significantly with design requirements, but the manufacturing cost is required to be gradually reduced. The packaging structure and technology using lead frames are still widely used because of their relatively low price. Traditional semiconductor packages that use lead frames as chip carriers, such as quad flat package (QFP) semiconductor packages or quad flat non-leaded (QFN) semiconductor packages, are made by first providing a lead frame with a die pad and multiple leads. Each lead of the lead frame has a connection pad at the end, and a protective layer is formed on the bottom surface of at least part of the connection pad with a metal with better chemical resistance and then rolled and flattened. Next, a semiconductor chip is bonded to the chip holder of the lead frame, and each pad on the semiconductor chip is electrically connected to a connection pad at the end of the corresponding lead pin by a gold wire, and the chip and the gold wire are covered with a packaging colloid, but the bottom surface of the chip holder and the plurality of lead pins is exposed. Then, the middle part of each lead pin is removed by a process such as chemical etching, leaving only the connection pads at the end of the lead pins and the protective layer on the bottom surface as the contact point for connecting the final product of the electronic package with the external circuit in actual application.
[0003] However, when etching the lead frame in the above-mentioned process using the existing lead frame, the etching rate along the flattened forming direction of the protective layer is slower than the etching rate in the forming direction perpendicular to the protective layer, resulting in the shape and size of the contacts left after etching being different from the shape and size originally designed, causing the finished electronic package to be unable to be correctly positioned and connected to the corresponding external circuits during actual application due to incorrect shape and size of the contacts, resulting in poor contact or even no conduction.
[0004] Therefore, how to overcome the above-mentioned problems of the prior art has become a difficult problem that needs to be overcome urgently in the industry. Utility Model Content
[0005] In view of the various deficiencies of the above-mentioned prior art, the present application provides a lead frame, including: a chip seat; and a plurality of connection pads, which are arranged around the chip seat, and a metal protection pad is formed on the bottom surface of at least a portion of the connection pads, and the metal protection pads respectively define a connection retention area and a processing area surrounding the connection retention area, and the metal protection pad and the plurality of connection pads are made of different materials.
[0006] The lead frame is defined with a forming direction, and the metal protection pad is flattened along the forming direction.
[0007] In the aforementioned lead frame, the width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is greater than the width of the processing area in a direction parallel to the forming direction.
[0008] In the aforementioned lead frame, the connection reserved area of each metal protection pad is rectangular, and its long side is perpendicular to the edge of one side of the lead frame where the metal protection pad is located.
[0009] In the aforementioned lead frame, the width of the processing area of each metal protection pad in the direction perpendicular to the forming direction is 1 to 1.23 times of its width in the direction parallel to the forming direction.
[0010] In the aforementioned lead frame, the connection reserved area of each metal protection pad is rectangular, and its long side is parallel to the edge of one side of the lead frame where the metal protection pad is located.
[0011] In the aforementioned lead frame, the width of the processing area of each metal protection pad in the direction perpendicular to the forming direction is 1 to 1.23 times of its width in the direction parallel to the forming direction.
[0012] In the aforementioned lead frame, the connection reservation area of each metal protection pad is rectangular, and part of the long sides of the metal protection pad are perpendicular to the edge of one side of the lead frame where the metal protection pad is located, and part of the long sides of the metal protection pad are parallel to the edge of one side of the lead frame where the metal protection pad is located.
[0013] In the aforementioned lead frame, the width of the processing area of each metal protection pad in the direction perpendicular to the forming direction is 1 to 1.23 times of its width in the direction parallel to the forming direction.
[0014] In the aforementioned lead frame, the connection reserved area of each metal protection pad is circular.
[0015] In the aforementioned lead frame, the width of the processing area of each metal protection pad in the direction perpendicular to the forming direction is 1 to 1.15 times of its width in the direction parallel to the forming direction.
[0016] The present application also provides a method for manufacturing an electronic package, comprising: providing a lead frame of any type as described above; combining an electronic component on the chip seat of the lead frame; electrically connecting the electronic component and each connection pad of the lead frame with a plurality of wires; covering the electronic component and the plurality of wires with a packaging material; and removing the processing area of each metal protection pad.
[0017] The manufacturing method of the electronic package also includes forming a protection layer on the lower surface of the connection pad without the metal protection pad after removing the processing area of each metal protection pad.
[0018] As can be seen from the above, the lead frame of the present application and the method for manufacturing an electronic package using the lead frame can prevent the shape and size of each contact of the electronic package manufactured using relatively cheap lead frame technology from having errors due to the different rates of etching processes along the forming direction perpendicular to the lead frame and along the forming direction parallel to the lead frame, thereby avoiding problems such as poor contact of the electronic package during use due to errors in the shape and size of the contacts. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figures 1A to 1E It is a schematic diagram of an embodiment of a method for manufacturing an electronic package of the present application.
[0020] FIG. 2A to FIG. 2D Schematic bottom views of different embodiments of the lead frame of the present application.
[0021] Figure 3A to Figure 3A-1 for FIG. 2A to FIG. 2C A partial enlarged schematic diagram of the bottom side of the metal protection pad.
[0022] Figure 3B for Figure 2D A partial enlarged schematic diagram of the bottom side of the metal protection pad.
[0023] Description of Reference Numerals
[0024] 1 Electronic packaging
[0025] 10 Lead frame
[0026] 11 Chip holder
[0027] 12 Connection pads
[0028] 13 Connecting arm
[0029] 14,15 Metal protection pad
[0030] 15a Connection Reserved Area
[0031] 15b Processing Area
[0032] 20 Electronic components
[0033] 30 Wire
[0034] 40 Encapsulation layer
[0035] 50 layers of protection
[0036] D f Forming direction
[0037] w x1 ,w x2 ,w x3 ,w y1 ,w y2 ,w y3 width
[0038] l1,l2 length
[0039] L x1 ,L x2 ,L y1 ,L y2 full length
[0040] D Diameter. DETAILED DESCRIPTION
[0041] The following describes the implementation methods of the present application through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification.
[0042] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings attached to this specification are only used to match the contents disclosed in the specification for the understanding and reading of those skilled in the art, and are not used to limit the limiting conditions for the implementation of this application, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical content disclosed in this application. At the same time, the terms such as "on", "first", "second", "one", etc. cited in this specification are only for the convenience of narration, and are not used to limit the scope of the implementation of this application. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of this application without substantially changing the technical content.
[0043] Figures 1A to 1E It is a schematic diagram of an embodiment of a method for manufacturing an electronic package of the present application.
[0044] like Figures 1A to 1E As shown, this embodiment discloses a method for manufacturing an electronic package. The method first comprises the following steps: Figure 1A A lead frame 10 is provided as shown. Figure 2A and Figure 3AThe lead frame 10 includes a chip holder 11 and a plurality of connection pads 12 arranged around the chip holder 11. A metal protection pad 15 is formed on the bottom surface of at least part of the connection pads 12 and is in close contact with the connection pads 12 to be electrically connected thereto. Each metal protection pad 15 defines a connection reservation area 15a and a processing area 15b surrounding the connection reservation area 15a. The chip holder 11 and the plurality of connection pads 12 are made of the same conductive material, while the metal protection pads 15 are made of another different conductive material. Generally speaking, the chip holder 11 is usually connected to each connection pad 12 by a plurality of structures such as connection arms 13, so as to fix the connection pads 12 around the chip holder 11. The chip seat 11, the connecting arm 13 and the connecting pad 12 are usually made of metal with better conductivity and better processability, such as a copper-containing alloy, while the material of the metal protection pad 15 is a metal with better chemical resistance, such as nickel (Ni), palladium (Pd), gold (Au), etc. or an alloy of any two or more of these materials.
[0045] The metal protection pad 15 defines a forming direction D f . Forming direction D f That is, the direction in which the metal protection pad 15 is flattened during the process of being formed on the bottom surface of the connection pads 12. More specifically, the forming direction D f That is, the direction in which the metal protection pad 15 is rolled and flattened, or the direction in which the crystal structure of the material of the metal protection pad 15 is stressed when the metal protection pad 15 is rolled and flattened. The processing area 15b of the metal protection pad 15 at the bottom of each connection pad 12 is made to be perpendicular to the forming direction D f The width is greater than its width in the direction parallel to the forming direction D f In some different embodiments, in addition to forming the metal protection pads 15 on the bottom surface of each connection pad 12, metal protection pads 14 may also be formed on the top surface of some connection pads 12 as needed, and this embodiment does not have any special limitation on this.
[0046] Next, an electronic component 20 (such as a semiconductor chip) is combined on the chip pad 11 of the lead frame 10 .
[0047] Then as Figure 1B As shown, the electronic component 20 is connected to each connection pad 12 of the lead frame 10 by a plurality of wires 30, so that each connection pad 12 is electrically connected to a contact point (not shown) on the electronic component 20. The wire 30 is, for example, a gold wire, but can also be a wire made of any other suitable conductive material.
[0048] Next, Figure 1C As shown, the electronic element 20 , the wires 30 and the lead frame 10 are coated with a packaging material to form a packaging layer 40 .
[0049] like Figure 1D As shown, each connection arm 13, a portion of each connection pad 12 and the processing area 15b of the metal protection pad 15 are removed by, for example, chemical etching, leaving the locally corroded connection pad 12 and the connection retention area 15a of the metal protection pad 15, so that an electronic package 1 such as a Multi Row Quad Flat Non-leaded (MR-QFN) type can be produced.
[0050] In the process of removing each connecting arm 13, a portion of each connecting pad 12 and the processing area 15b of each metal protection pad 15, since each metal protection pad 15 has a processing area 15b outside the connection reserved area 15a, and the processing area 15b of each metal protection pad 15 is perpendicular to the forming direction D f The width is greater than its width in the direction parallel to the forming direction D f width, so even along the parallel forming direction D f The etching rate on the vertical forming direction D f Although the etching rate is slow, after the etching is completed, the processing area 15b of each metal protection pad 15 can still be accurately removed, leaving only the connection reservation area 15a whose shape and size meet the design.
[0051] like Figure 1E As shown, in some preferred embodiments, after removing the processing area 15b of each metal protection pad 15, a protection layer 50 may be further formed on the lower surface of the connection pad 12 (as a circuit) without the metal protection pad 15. The material of the protection layer 50 is, for example, a solder mask such as solder mask paint, but is not limited thereto.
[0052] In the method for manufacturing the electronic package of this embodiment, the metal protection pad 15 and its connection reserved area 15a can have different shapes. Figure 2A In some embodiments shown in FIG. 1 , the connection reserved area 15a of each metal protection pad 15 is rectangular, and its long side is perpendicular to the edge of one side of the lead frame 10 where the metal protection pad 15 is located. Figure 3A and Figure 3A-1 In this embodiment, the processing area 15b of each metal protection pad 15 is perpendicular to the forming direction D f The width of the f 1 to 1.23 times the width.
[0053] More specifically, in this embodiment, the Figure 2A The shapes of the metal protection pads 15 on the upper and lower sides of the chip holder 11 are as follows: Figure 3AAs shown in the figure: if the widths of the processing areas 15b on the left and right sides of the connection reserved area 15a of the metal protection pad 15 are w x1 , and the widths of the processing areas 15b located on the upper and lower sides of the connection reserved area 15a are w y1 .lie in Figure 2A The shapes of the metal protection pads 15 on the left and right sides of the chip holder 11 are as follows: Figure 3A-1 As shown, the widths of the processing areas 15b on the left and right sides of the connection reserved area 15a of the metal protection pad 15 are w x2 , and the widths of the processing areas 15b located on the upper and lower sides of the connection reserved area 15a are w y2 . Then Figure 2A As for the metal protection pads 15 on the upper and lower sides of the chip holder 11, w x2 ≦w y1 ≦1.23w x2 , that is, w y1 w x2 1 to 1.23 times, and the total length L of the long side of the metal protection pad 15 y1 =l1+2w y1 , the total length of its short side is L x1 =l2+2w x1 . Figure 2A For the metal protection pads 15 on the left and right sides of the chip holder 11, w x1 ≦w y2 ≦1.23w x1 , that is, w y2 The same is w x1 1 to 1.23 times the total length L of the long side of the metal protection pad 15 x2 =l1+2w x2 , the total length of its short side is L y2 =l2+2w y2 In other words, the metal protection pads 15 located on the upper and lower sides of the chip base 11 before etching are different in size from the metal protection pads 15 located on the left and right sides of the chip base 11. However, the connection reserved area 15a left after etching is completed, regardless of which side of the chip base 11 it is located on, will be a rectangle with a long side length of l1 and a short side length of l2.
[0054] Similarly, in Figure 2B In the embodiment shown, the connection reserved area 15a of each metal protection pad 15 is also rectangular, but its long side is parallel to the edge of one side of the lead frame 10 where the metal protection pad 15 is located. In this embodiment, the size of each metal protection pad 15 located on the upper and lower sides of the chip holder 11 is configured as follows: Figure 3A-1 As shown, the size configuration of each metal protection pad 15 located on the left and right sides of the chip base 11 is as follows Figure 3AAs shown, the processing area 15b of each metal protection pad 15 is perpendicular to the forming direction D f The width on the surface is still the same as that on the surface parallel to the forming direction D f The connection reserved area 15a left after etching is also a rectangle with a long side length of l1 and a short side length of l2.
[0055] Alternatively, the metal protection pad 15 may be arranged as follows: Figure 2C As shown, the connection reserved area 15a of each metal protection pad 15 is also rectangular, but the long sides of some of the metal protection pads 15 are perpendicular to the edge of the side of the lead frame 10 where the metal protection pad 15 is located, and the long sides of some of the metal protection pads 15 are parallel to the edge of the side of the lead frame 10 where the metal protection pad 15 is located. Even so, the processing area 15b of each metal protection pad 15 is perpendicular to the forming direction D f The width of the f 1 to 1.23 times the width.
[0056] In addition to being rectangular, the connection reserved area 15a of each metal protection pad 15 may also be Figure 2D In this embodiment, the shape and size of each metal protection pad 15 are configured as follows: Figure 3B As shown, the connection reserved area 15a is a circle with a diameter D, and the processing area 15b is perpendicular to the forming direction D. f The width w y3 For it is parallel to the forming direction D f The width w x3 Thus, the connection reserved area 15a left after etching is a circle with a diameter D.
[0057] The present embodiment also discloses a lead frame 10, comprising: a chip base 11; and a plurality of connection pads 12, which are arranged around the chip base 11, and a metal protection pad 15 is formed on the bottom surface of at least a portion of the connection pad 12, and the metal protection pad 15 defines a connection reservation area 15a and a processing area 15b surrounding the connection reservation area 15a, and the metal protection pad 15 and the plurality of connection pads 12 are made of different materials. The lead frame 10 and its various embodiments are the same as those adopted and illustrated in the above-mentioned electronic package manufacturing method embodiment, so they will not be repeated here.
[0058] In summary, the method for manufacturing the electronic package shown in this embodiment and the lead frame used in the method can ensure that the shape and size of each contact of the manufactured electronic package will not have errors due to the different rates of processes such as etching along the forming direction perpendicular to the metal protection pad and along the forming direction parallel to the metal protection pad, thereby avoiding problems such as poor contact of the electronic package during use due to errors in the shape and size of the contacts.
[0059] The above embodiments are only used to illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art may modify the above embodiments without violating the spirit and scope of the present application. Therefore, the scope of protection of the present application should be as listed in the claims.
Claims
1. A lead frame, characterized in that: include: Chip holder; as well as A plurality of connection pads are arranged around the chip seat. A metal protection pad is formed on the bottom surface of at least part of the connection pads. The metal protection pad defines a connection reservation area and a processing area surrounding the connection reservation area. The metal protection pad and the plurality of connection pads are made of different materials.
2. The lead frame according to claim 1, wherein: The lead frame defines a forming direction, and the metal protection pad is flattened along the forming direction.
3. The lead frame according to claim 2, wherein: The width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is greater than the width of the processing area in a direction parallel to the forming direction.
4. The lead frame according to claim 3, wherein: The connection reserved area of each metal protection pad is rectangular, and the long side of the connection reserved area is perpendicular to the edge of one side of the lead frame where the metal protection pad is located.
5. The lead frame according to claim 4, wherein: The width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is 1 to 1.23 times its width in a direction parallel to the forming direction.
6. The lead frame according to claim 3, wherein: The connection reserved area of each metal protection pad is rectangular, and its long side is parallel to the edge of one side of the lead frame where the metal protection pad is located.
7. The lead frame according to claim 6, wherein: The width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is 1 to 1.23 times its width in a direction parallel to the forming direction.
8. The lead frame according to claim 3, wherein: The connection reservation area of each metal protection pad is rectangular, and part of the long sides of the metal protection pad are perpendicular to the edge of one side of the lead frame where the metal protection pad is located, and part of the long sides of the metal protection pad are parallel to the edge of one side of the lead frame where the metal protection pad is located.
9. The lead frame according to claim 8, wherein: The width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is 1 to 1.23 times its width in a direction parallel to the forming direction.
10. The lead frame according to claim 3, wherein: The connection reserved area of each metal protection pad is circular.
11. The lead frame according to claim 10, wherein: The width of the processing area of each metal protection pad in a direction perpendicular to the forming direction is 1 to 1.15 times its width in a direction parallel to the forming direction.