Lead frame
By introducing through slots and connecting ribs into the leadframe, the warpage problem of the leadframe during QFN packaging was solved, resulting in higher packaging yield.
Patent Information
- Application Number
- CN202422754061.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-12
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2034-11-12
AI Technical Summary
The existing leadframe warps during QFN packaging due to its rigidity and high stress, affecting normal operation.
Design a lead frame that includes through slots to disconnect adjacent rows of lead frame units and connects them with reinforcing bars to release stress and prevent warping.
It effectively prevents and reduces overall warping of the lead frame, improving packaging yield.
Smart Images
Figure CN223598716U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of semiconductor packaging, and in particular to a lead frame. BACKGROUND
[0002] As a part of semiconductor packaging, the lead frame is used to support the packaged semiconductor chip and to connect the packaged semiconductor chip with external devices.
[0003] The existing lead frame generally includes a plurality of lead frame units arranged in rows and columns, each of which includes a base island and a plurality of discrete pins located around the base island, and the adjacent lead frame units are connected by webs in the row direction and the column direction.
[0004] When the lead frame is applied to a package in the form of QFN (Quad Flat No-leads Package) or the like, due to the hard texture of the lead frame itself and the large stress of one-time injection during the packaging process, the lead frame as a whole will be warped (the maximum warping is up to 10 mm), and the warping is ineffective through heating and shaping, which affects the normal operation. CONTENT OF THE INVENTION
[0005] The technical problem to be solved by the present application is to provide a lead frame to prevent or reduce the overall warping of the lead frame.
[0006] To this end, the present application provides a lead frame, comprising:
[0007] a frame body, the frame body including a plurality of discrete lead frame units arranged in rows and columns, and webs connecting the corresponding two lead frame units between the two adjacent lead frame units of the adjacent rows;
[0008] The two adjacent columns of lead frame units have a through slot, which disconnects the two adjacent columns of lead frame units.
[0009] In an optional embodiment, the size of the frame body in the row direction is greater than the size in the column direction.
[0010] In an optional embodiment, the size of the frame body in the row direction is 200-300 mm, and the size of the frame body in the row direction is 50-90 mm.
[0011] In an optional embodiment, each of the lead frame units includes a base island and discrete pins located around or on both sides of the base island, a gap between adjacent pins, and a barrier wall covering part of the upper surface of the pins and filling the gap between the pins.
[0012] In an optional embodiment, the length of the through slot is greater than or equal to the length of each column of lead frame units, and the width of the through slot is less than or equal to the distance between the outer side of the pin in a column of lead frame units and the outer side of the pin in an adjacent column of lead frame units.
[0013] In an optional embodiment, the length of the through groove is 48 mm - 88 mm. The width of the through groove is 1.8 mm - 3 mm.
[0014] In one optional embodiment, the retaining wall is made of molding compound.
[0015] In one alternative embodiment, the frame body is made of metal or alloy, and the surface of the pins also has an electroplated metal layer.
[0016] In an alternative embodiment, the frame body further includes a border surrounding and connected to the plurality of discrete, row-and-column arranged lead frame units.
[0017] In an optional embodiment, the frame has positioning holes.
[0018] In an optional embodiment, the pin has a through hole extending through the upper and lower surfaces of the pin, and the retaining wall also fills the through hole.
[0019] In one optional embodiment, the pin includes an inner pin and a pin rib connected together, the inner pin being close to the base island and the pin rib being away from the base island, and the through hole being located on the side of the inner pin close to the pin rib, or the through hole being located between the inner pin and the pin rib.
[0020] The advantages of the technical solution in this application are:
[0021] The lead frame in this application includes: a frame body, which comprises a plurality of discrete lead frame units arranged in rows and columns, and connecting ribs that connect two adjacent lead frame units in adjacent rows; a through slot is provided between two adjacent columns of lead frame units, the through slot separating the two adjacent columns of lead frame units. In this application, two adjacent lead frame units in adjacent rows are connected by the corresponding connecting ribs, and a through slot is provided between two adjacent columns of lead frame units, the through slot effectively and to a large extent releases stress in the lead frame, thereby preventing and reducing the overall warping of the lead frame. Furthermore, this structure can reduce the overall flexibility of the lead frame, allowing each column of lead frame units to better adhere to the vacuum pad of the workbench during subsequent encapsulation, which is more conducive to improving the yield rate. Attached Figure Description
[0022] Figure 1 This is a top view of the lead frame structure in one embodiment of this application;
[0023] Figure 2 for Figure 1 A top view of one of the lead frame units;
[0024] Figure 3 for Figure 1 A bottom view of the structure of a lead frame unit;
[0025] Figure 4 The first image is Figure 2 A schematic diagram of the cross-sectional structure along the cutting line BB; the second figure is... Figure 2 A schematic diagram of the cross-sectional structure along the cutting line B1B1, the third figure is... Figure 3 A schematic diagram of the cross-sectional structure along the cutting line AA;
[0026] Figure 5 The first image is Figure 2 A schematic diagram of the cross-sectional structure along the cutting line CC direction; the second figure is... Figure 2 A schematic diagram of the cross-sectional structure along the cutting line DD direction; the third figure is... Figure 3 A schematic diagram of the cross-sectional structure along the cutting line EE direction;
[0027] Figure 6 for Figure 2 A schematic diagram of a structure with retaining walls based on the existing structure;
[0028] Figure 7 The first image is Figure 6 A schematic diagram of the cross-sectional structure along the cutting line BB; the second figure is... Figure 6 A schematic diagram of the cross-sectional structure along the cutting line B1B1, the third figure is... Figure 6 A schematic diagram of the cross-sectional structure along the cutting line AA. Detailed Implementation
[0029] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. In describing the embodiments of this application in detail, for ease of explanation, the schematic diagrams may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of this application. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.
[0030] One embodiment of this application provides a lead frame, referencing... Figure 1 The lead frame includes:
[0031] The frame body comprises a plurality of separate lead frame units 101 arranged in rows and columns, and webs 102 connecting two adjacent lead frame units 101 in adjacent rows.
[0032] The two adjacent columns of lead frame units 101 are separated by through grooves 103.
[0033] The lead frame is used to support the packaged semiconductor chips and connect the packaged semiconductor chips with external devices during packaging. In an embodiment, the lead frame can be used for packaging in the form of QFN (Quad Flat No-leads Package). The material of the frame body of the lead frame is metal or alloy. In a specific embodiment, the material of the frame body of the lead frame is copper.
[0034] The frame body comprises a plurality of separate lead frame units 101 arranged in rows and columns, and webs 102 connecting two adjacent lead frame units 101 in adjacent rows. The material of the webs 102 is the same as that of the frame body. In an embodiment, the frame body further comprises a frame 107 surrounding and connecting the plurality of separate lead frame units 101 arranged in rows and columns. The frame 107 has positioning holes (not shown in the figure) for positioning during subsequent packaging. Each of the lead frame units 101 can be used to package at least one semiconductor chip, and each of the lead frame units 101 corresponds to a packaging structure. After packaging, the webs 102 and the frame 107 can be cut off to form a plurality of separate packaging structures.
[0035] The plurality of lead frame units 101 are arranged in rows and columns, such as an N×M array, where N is greater than M, N is at least 3, and M is at least 2. N is the number of lead frame units 101 in each row, and M is the number of lead frame units 101 in each column. It should be noted that, in an embodiment, as shown in Figure 1 The column is in the Y-axis direction. Figure 1 Figure 1 The column is in the Y-axis direction.
[0036] The structure of the lead frame unit 101 will be described in detail below. In an embodiment, reference is made to Figures 1-4 Figure 2 Figure 1 Figure 3 Figure 1 A bottom view of one leadframe unit 101, Figure 4 A top view of one leadframe unit 101, Figure 2 A cross-sectional view along the cutting line BB, Figure 2 A cross-sectional view along the cutting line B1B1, Figure 3 A cross-sectional view along the cutting line AA, Figure 5 A top view of one leadframe unit 101, Figure 2 A cross-sectional view along the cutting line CC, Figure 2 A cross-sectional view along the cutting line DD, Figure 3 A cross-sectional view along the cutting line EE. Each leadframe unit 101 comprises a base island 104 and a plurality of leads 105 separated from each other around or on both sides of the base island 104, with gaps 113 (refer to Figure 2 or Figure 3 ) between adjacent leads 105. In one embodiment, the base island 104 is square-shaped, and the plurality of leads 105 are on both sides or around the base island 104. In one embodiment, the lead 105 comprises an inner lead 105a connected to a lead tie 105b, the inner lead 105a is close to the base island 104, and the lead tie 105b is away from the base island 104, the plurality of inner leads 105a are separated from each other, and the inner lead 105a close to the base island 104 is separated from the base island 104, part of the lead ties 105b are also separated from each other, the plurality of inner leads 105a and part of the lead ties 105b have gaps 113 (refer to Figure 2 or Figure 3 or Figure 5 ), the plurality of inner leads 105a and the base island 104 also have gaps 111 (refer to Figure 2 , Figure 3 or Figure 4 ), the end of the plurality of inner leads 105a away from the base island 104 is connected to the lead tie 105b, the end of the plurality of lead ties 105b not connected to the inner lead 105a is connected together, the outermost lead tie 105b of each leadframe unit 101 is on the left and right sides, and the lead ties 105b of the adjacent two columns of leadframe units 101 have the through slot 103 (refer to Figure 1 ) therebetween. In one embodiment, the area outside the inner lead 105a in one leadframe unit 101 is the cutting path 11, and after packaging, the cutting path 11 is cut to remove the tie 102 and the lead tie 105b outside the cutting path 11, and the base island 104 and the inner lead 105a inside the cutting path 11 are retained as part of the packaging structure.
[0037] In an embodiment, referring to Figure 3 and Figure 4 , the pin 105 has a through hole 112 through the upper and lower surfaces of the pin to strengthen the binding force between the subsequently formed barrier wall and the pin.
[0038] In an embodiment, the through hole 112 is located on one side of the inner pin 105a close to the pin web 105b, and after subsequent cutting, the through hole 112 is completely retained.
[0039] In an embodiment, the through hole 112 is located between the inner pin 105a and the pin web 105b, and after subsequent cutting, the through hole 112 is partially cut off.
[0040] In an embodiment, referring to Figure 2 and Figure 5 , the upper surface of the base island 104 has a positioning groove 116, which is used for positioning in the subsequent packaging process. In an embodiment, the shape of the positioning groove 116 is a "cross" shape.
[0041] In an embodiment, referring to Figure 6 and Figure 7 , wherein Figure 6 is the structural diagram of the base island 104 with a barrier wall, Figure 2 , the first figure is Figure 7 the cross-sectional structural diagram along the cutting line BB direction, the second figure is Figure 6 the cross-sectional structural diagram along the cutting line B1B1 direction, and the third figure is Figure 6 the cross-sectional structural diagram along the cutting line AA direction, each lead frame unit 101 further comprises a barrier wall 106 covering part of the upper surface of the pin 105 and filling the gap 113 between the pins 105 (referring to Figure 6 or Figure 2 or Figure 3 or Figure 5 , in a specific embodiment, the barrier wall 106 covers the upper surface of part of the inner pin 105a (or can also cover part of the upper surface of the pin web 105b), and the barrier wall 106 exposes the upper surface of the inner pin 105a close to the base island 104 side for subsequent bonding of the lead wire and the inner pin 105a for electrical connection. The barrier wall 106 covering part of the upper surface of the pin 105 and filling the gap 113 between the pins 105 surrounds a cavity for subsequent placement of a chip, which on the one hand limits the space for subsequent packaging, and on the other hand, the barrier wall 106 can also fix the pin 105 during packaging.
[0042] In one embodiment, the barrier wall 106 can include a main portion and a peripheral portion, the main portion is located in the upper surface of the inner lead 105a and the gap 113 between the inner lead 105a, the peripheral portion is located in the remaining gap on both sides, the thickness of the peripheral portion is smaller than the thickness of the main portion, which can reduce the difficulty of subsequent cutting while improving the fixation. When cutting subsequently, the peripheral portion of the barrier wall 106 is cut off, and the main portion of the barrier wall 106 is not cut off.
[0043] In one embodiment, the material of the barrier wall 106 is plastic packaging material. In one embodiment, the material of the plastic packaging material can be filled or unfilled epoxy resin, polyimide resin, benzocyclobutene resin or polybenzoxazole resin; or it can also be filled with polybutylene terephthalate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polyolefin, polyurethane, polyolefin, polyether sulfone, polyamide, polyurethane, ethylene-vinyl acetate copolymer or polyvinyl alcohol. The filler can be inorganic or organic.
[0044] In one embodiment, the gap 111 between the lead 105 and the base island 104 (see Figure 2 or Figure 3 ) has a filling layer 114. The material of the filling layer 114 is the same as the material of the barrier wall 106, and the material of the filling layer 114 is also plastic packaging material.
[0045] In one embodiment, referring to Figures 2-4 or Figure 7 , part of the surface of the lead 105 and the base island 104 also has a plated metal layer 110, which is used to protect the lead 105. In one embodiment, the material of the plated metal layer 110 is one or more of silver, copper or nickel.
[0046] Continuing to refer to Figure 1 , two adjacent lead frame units 101 in adjacent rows are connected by the corresponding webs 102, and the two adjacent columns of lead frame units 101 have through grooves 103 that separate the two adjacent columns of lead frame units 101, which can effectively and to a large extent release the stress in the lead frame, thereby preventing and reducing the overall warping of the lead frame. And such a structure can also reduce the overall flexibility of the lead frame, so that each column of lead frame units 101 can better adhere to the vacuum pad of the working machine during subsequent packaging, which is more conducive to improving the yield of the operation.
[0047] The length of the through slot 103 is greater than or equal to the length of each column of lead frame units 101 (the length of each column of lead frame units 101 is the size of the column of lead frame units 101 in the Y-axis direction), and the width of the through slot 103 is less than or equal to the distance between the outer sides of the pins in the lead frame units 101 of a certain column and the outer sides of the pins in the lead frame units 101 of the adjacent column. This design can effectively and to a greater extent release the stress in the lead frame while ensuring the mechanical stability of the lead frame, thereby better preventing and reducing the warping of the entire lead frame.
[0048] In an embodiment, the size of the frame body in the row direction is 200-300 mm, the size of the frame body in the row direction in the column direction is 50-90 mm, the length of the through slot 103 is 48-88 mm, and the width of the through slot 103 is 1.8-3 mm.
[0049] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application using the disclosed methods and technical contents without departing from the spirit and scope of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments in accordance with the technical essence of the present application, which does not deviate from the technical solutions of the present application, shall fall within the protection scope of the technical solutions of the present application.
Claims
1. A lead frame, characterized in that, include: The frame body includes a plurality of discrete lead frame units arranged in rows and columns and connecting ribs that connect two adjacent lead frame units located in adjacent rows. There is a through slot between two adjacent columns of lead frame units, which disconnects the two adjacent columns of lead frame units.
2. The lead frame as described in claim 1, characterized in that, The dimensions of the frame body in the row direction are larger than its dimensions in the column direction.
3. The lead frame as described in claim 1, characterized in that, The frame body has a row dimension of 200mm-300mm and a column dimension of 50mm-90mm.
4. The lead frame as described in claim 1 or 2, characterized in that, Each of the lead frame units includes a base island and pins located around or on both sides of the base island, with gaps between adjacent pins, and a retaining wall covering a portion of the upper surface of the pins and filling the gaps between the pins.
5. The lead frame as described in claim 4, characterized in that, The length of the through slot is greater than or equal to the length of each column of lead frame units, and the width of the through slot is less than or equal to the distance between the outer side of the pin in a column of lead frame units and the outer side of the pin in the adjacent column of lead frame units.
6. The lead frame as described in claim 5, characterized in that, The length of the through groove is 48 mm - 88 mm, and the width of the through groove is 1.8 mm - 3 mm.
7. The lead frame as described in claim 4, characterized in that, The retaining wall is made of molding compound.
8. The lead frame as described in claim 4, characterized in that, The frame body is made of metal or alloy, and the surface of the pins also has an electroplated metal layer.
9. The lead frame as described in claim 1, characterized in that, The frame body also includes a border surrounding and connected to the plurality of discrete lead frame units arranged in rows and columns.
10. The lead frame as described in claim 9, characterized in that, The frame has positioning holes.
11. The lead frame as described in claim 4, characterized in that, The pin has a through hole that extends through the upper and lower surfaces of the pin, and the retaining wall also fills the through hole.
12. The lead frame as described in claim 11, characterized in that, The pin includes an inner pin and a pin connecting rib connected together. The inner pin is close to the base island, and the pin connecting rib is away from the base island. The through hole is located on the side of the inner pin close to the pin connecting rib, or the through hole is located between the inner pin and the pin connecting rib.