Lead frame

Abstract

The invention provides a lead frame which comprises a frame unit which comprises a pin; the frame connecting ribs are arranged between the adjacent frame units, each frame connecting rib comprises a base body and a microstructure, the base bodies are connected with the pins, the microstructures are arranged on the base bodies, and the configuration of the microstructures is related to the width of the base bodies; therefore, the amount of copper cuttings generated during the first cutting with the set width is reduced or even eliminated. According to the lead frame provided by the invention, burr abnormity of a packaged product adopting step cutting is avoided, and the yield of the packaged product is further improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor packaging, and in particular to a lead frame. Background Art

[0002] Wettable Flank Quad Flat No-leads Package (QFN) products can achieve tinning on the side of the pins. Compared with traditional QFN products, they have wettable flanks and have high welding capabilities. They are mostly used in automobiles, military industry, medical equipment, etc.

[0003] There are currently two common wettable flank QFN processes in the industry. One process is pin dimple drilling (Dimple / Cavity), and the other is pin step cutting (Step Cutting). The dimples of the pin dimple drilling packaging structure are prone to burrs, so the step cutting technical solution is widely used.

[0004] Currently, the frame dambar width of the packaging products using step cutting is less than or equal to 0.2mm, and the yield is high and stable. However, products with a frame dambar width greater than 0.2mm and a product thickness greater than 2mm have a small amount of burr abnormalities due to design and process factors, and the yield of the packaging products cannot meet the requirements. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a lead frame which can reduce or even avoid the generation of abnormal burrs in packaged products using step cutting, thereby improving the yield of packaged products.

[0006] In order to solve the above problems, an embodiment of the present invention provides a lead frame, including: a frame unit, the frame unit including a pin; a frame connecting rib, which is arranged between adjacent frame units, the frame connecting rib including a substrate and a microstructure, the substrate is connected to the pin, the microstructure is arranged on the substrate, and the configuration of the microstructure is associated with the width of the substrate, so as to reduce or even eliminate the amount of copper chips generated when performing the first cut with a set width.

[0007] In one embodiment, the substrate has a first width, which is less than the set width and greater than or equal to two-thirds of the set width, and the microstructure is at least one of a through hole passing through the substrate or a groove recessed into the substrate, and the width of the through hole or the groove is less than the first width.

[0008] In one embodiment, the through hole or the groove is arranged between pins of two adjacent frame units.

[0009] In one embodiment, the through hole or the groove is arranged in a region of the base body that does not correspond to the pin.

[0010] In one embodiment, the cross-sectional area of ​​the through hole or the groove is 1 / 4 to 1 / 3 of the cross-sectional area of ​​the pin.

[0011] In one embodiment, the frame connecting bar includes a plurality of the through holes or the grooves, and the plurality of the through holes or the grooves are evenly distributed in the extension direction of the base.

[0012] In one embodiment, the through hole or the groove is arranged on the center line of the base.

[0013] In one embodiment, the substrate has a second width, which is less than two-thirds of the set width and greater than one-third of the set width. The microstructure is a convex strip arranged on the surface of the substrate, and the convex strip extends along the extension direction of the substrate. The width of the convex strip is less than the second width.

[0014] In one embodiment, the width of the convex strip is 1 / 3 to 1 / 2 of the second width.

[0015] In one embodiment, the surface of the protruding strip is flush with the surface of the pin, or the surface of the protruding strip is lower than the surface of the pin.

[0016] In one embodiment, the convex strip is arranged on the center line of the base.

[0017] In one embodiment, a surface of the base is lower than a surface of the pin.

[0018] In one embodiment, the width of the area of ​​the substrate connected to the pin is greater than the width of the area not connected to the pin.

[0019] In the lead frame provided by the embodiment of the present invention, the frame connecting rib is composed of a substrate and a microstructure, the configuration of the microstructure is related to the width of the substrate, and the two are arranged in association, so that the volume of the frame connecting rib located in the cutting path of the set width is reduced while ensuring the strength of the frame connecting rib. Among them, reducing the volume of the frame connecting rib in the cutting path can reduce or even eliminate the amount of copper chips generated by the first cutting in the step cutting process, thereby reducing or even avoiding the generation of abnormal burrs of the packaged product using step cutting, thereby improving the yield of the packaged product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is a bottom view of a lead frame provided by a first embodiment of the present invention;

[0022] Figure 2 is along Figure 1 A cross-sectional view of line A-A1;

[0023] Figure 3 is along Figure 1 Cross-sectional view of line B-B1;

[0024] Figure 4 The lead frame provided by the second embodiment of the present invention is Figure 1 Cross-sectional view at the A-A1 line;

[0025] Figure 5 is a bottom view of a lead frame provided by a third embodiment of the present invention;

[0026] Figure 6 is along Figure 5 A cross-sectional view of line A-A1;

[0027] Figure 7 is along Figure 5 Cross-sectional view along line B-B1. DETAILED DESCRIPTION

[0028] As described in the background art, packaged products using step cutting are prone to burr anomalies, and the reliability of packaged products cannot meet the requirements. The inventor has conducted in-depth research on this.

[0029] The step cutting process is usually divided into two cuttings. The first cutting of the plastic package structure removes some pins and frame ribs. After the first cutting, electroplating is performed. After electroplating, a second cutting is performed to form an independent packaging structure. In the cutting process, in order to save costs, diamond is usually used as a cutting knife to reduce the wear of the cutting knife. The inventor found that the blade is wrapped with copper during the cutting process. While the wear of the cutting knife is reduced, the cutting force of the cutting knife is also reduced. The cut copper chips are not easy to discharge and accumulate and extend in the cutting path; when electroplating is performed, the accumulated extension area will also be electroplated; during the second cutting, the accumulated copper chips will extend under the extrusion of the cutting knife, forming burrs on the edge of the step, causing abnormal burrs in the packaging structure and affecting the product yield.

[0030] In view of this, an embodiment of the present invention provides a lead frame, which can reduce or even avoid the generation of abnormal burrs in a packaged product using step cutting, thereby improving the yield of the packaged product.

[0031] The specific implementation of the lead frame provided by the present invention is described in detail below with reference to the accompanying drawings.

[0032] See also Figure 1 to Figure 3 ,in, Figure 1 is a bottom view of a lead frame provided by the first embodiment of the present invention, Figure 2 is along Figure 1 The cross-sectional view of the A-A1 line, Figure 3 is along Figure 1 In the cross-sectional view along the line B-B1, the lead frame includes: a frame unit 100, the frame unit 100 includes a lead 101; a frame connecting rib 110, which is arranged between adjacent frame units 100, the frame connecting rib 110 includes a substrate 111 and a microstructure, the substrate 111 is connected to the lead 101, the microstructure is arranged on the substrate 111, and the configuration of the microstructure is associated with the width of the substrate 111, so as to reduce or even eliminate the amount of copper chips generated when performing the first cut with a set width. The setting of the microstructure can reduce the volume of the frame connecting rib 110 in the cutting path 200 with a set width W3 and increase the strength of the frame connecting rib 110.

[0033] The lead frame includes a plurality of frame units 100, each of which includes a base island 102 and pins 101 disposed around the base island 102, and the base islands 102 and the pins 101 of adjacent frame units 100 are connected by the frame dambar 110. Figure 1 Only one complete frame unit 100 is schematically shown in the figure, and only the pins 101 of other frame units 100 around the frame unit 100 are shown.

[0034] In the lead frame provided by the embodiment of the present invention, the frame connecting rib 110 is composed of a substrate 111 and a microstructure, the configuration of the microstructure is related to the width of the substrate 111, and the two are arranged in association, so that the volume of the frame connecting rib 110 located in the cutting road 200 of the set width W3 is reduced while ensuring the strength of the frame connecting rib 110. Among them, reducing the volume of the frame connecting rib 110 in the cutting road 200 can reduce or even eliminate the amount of copper chips generated by the first cutting in the step cutting process, thereby reducing or even avoiding the generation of abnormal burrs of the packaged product using step cutting, thereby improving the yield of the packaged product.

[0035] The cutting path 200 is set between adjacent frame units 100, and the width of the cutting path is greater than or equal to the gap between adjacent frame units 100. In the step cutting process, the first cutting is performed along the cutting path 200, and the set width W3 of the first cutting is greater than the cutting path width, then the end of the pin 101 of the frame unit 100 connected to the frame connecting bar 110 is also partially cut, so that a step can be formed at the pin 101. Figure 2 The dotted line in FIG. 2 shows the cutting path 200. Subsequently, a second cutting is performed along the cutting path 200 to form an independent packaging structure, and the cutting width of the second cutting is the cutting path width.

[0036] The area where the cutting road 200 is located covers the area where the frame connecting bar 110 is located, and the area of ​​the area where the cutting road 200 is located is larger than the area of ​​the area where the frame connecting bar 110 is located, so as to ensure that the frame connecting bar 110 can be completely removed during the second cutting in the step cutting process.

[0037] The base 111 is disposed between adjacent frame units 100, and the base 111 extends along the gap between adjacent frame units 100. In this embodiment, the base 111 has a first width W1, the first width W1 is less than or equal to the cutting road width, the first width W1 is less than the set width W3 and greater than or equal to two-thirds of the set width W3, and the microstructure is a through hole 112 penetrating the base 111 or a groove 113 recessed into the base 111 (see Figure 4 ), the width of the through hole 112 or the groove 113 is smaller than the first width W1. The first width W1 of the base 111 refers to the width of the base 111 in a direction perpendicular to the extension direction of the base 111.

[0038] The first width W1 of the substrate 111 is less than or equal to the cutting line width, that is, the entire substrate 111 is located within the cutting line 200, which can ensure that the frame connecting rib 110 is completely cut off during the step cutting process; the first width W1 of the substrate 111 is greater than or equal to two-thirds of the set width W3, which can ensure the strength of the frame connecting rib 110, and further ensure the supporting strength of the frame connecting rib 110 to the pin 101 and the base island 102.

[0039] In this embodiment, the microstructure is a through hole 112 that penetrates the substrate 111, and the width of the through hole 112 is less than the first width W1. Compared with the structure in which the frame connecting bar 110 is entirely composed of the substrate 111, the volume of the frame connecting bar 110 can be reduced by setting the through hole 112 in this embodiment, thereby reducing or even eliminating the amount of copper scraps generated by the first cutting in the step cutting process. The shape of the cross section of the through hole 112 includes but is not limited to a circle, an ellipse, a rectangle, a triangle, a polygon, etc.

[0040] In the second embodiment, see Figure 4 , which is a lead frame provided by the second embodiment of the present invention along Figure 1 In the cross-sectional view at the position of the A-A1 line, the microstructure is a groove 113 that is recessed into the substrate 111, and the width of the groove 113 is less than the first width W1. Compared with the structure in which the frame connecting rib 110 is entirely composed of the substrate 111, the volume of the frame connecting rib 110 can be reduced by setting the groove 113 in this embodiment, thereby reducing or even eliminating the amount of copper scraps generated by the first cutting in the step cutting process; and compared with setting the through hole 112, the strength of the frame connecting rib 110 can be further enhanced by setting the groove 113 in this embodiment. The shape of the cross section of the groove 113 includes but is not limited to a circle, an ellipse, a rectangle, a triangle, a polygon, etc.

[0041] In the above embodiments, the through hole 112 or the groove 113 is provided on the base 111. In other embodiments, the through hole 112 and the groove 113 can be provided on the base 111 at the same time, and the through hole 112 and the groove 113 are spaced apart from each other, thereby further ensuring the strength of the frame connecting bar 110 while reducing the volume of the frame connecting bar 110.

[0042] In some embodiments, the frame connecting bar 110 includes a plurality of the through holes 112 or the grooves 113 , and in the extension direction of the base 111 , the plurality of the through holes 112 or the grooves 113 are evenly distributed to ensure the strength of the frame connecting bar 110 .

[0043] In some embodiments, the through hole 112 or the groove 113 is disposed between the pins 101 of two adjacent frame units 100, for example. Figure 1As shown, the through hole 112 is arranged between the pins 101 of two adjacent frame units 100. The through hole 112 or the groove 113 is arranged between the pins 101 of two adjacent frame units 100, which reduces the frame connecting ribs 110 between the pins 101, thereby reducing the amount of copper scraps generated at the pins 101 during the step cutting process. Even if burrs are generated during the step cutting process, these burrs will not exist at the pins 101, thereby preventing the burrs from connecting adjacent pins 101. Wherein, the adjacent pins 101 include adjacent pins 101 of the same frame unit 100 or adjacent pins 101 of different frame units 100.

[0044] In other embodiments, the through hole 112 or the groove 113 may not be arranged between the pins 101 of two adjacent frame units 100, but may be located in an area of ​​the base 111 that does not correspond to the pin 101; or, part of the through holes 112 or the groove 113 may be arranged between the pins 101 of two adjacent frame units 100, and another part of the through holes 112 or the groove 113 may be located in an area of ​​the base 111 that does not correspond to the pin 101.

[0045] In some embodiments, the cross-sectional area of ​​the through hole 112 or the groove 113 is 1 / 4 to 1 / 3 of the cross-sectional area of ​​the pin 101. Figure 1 As shown, the cross-sectional area of ​​the through hole 112 is 1 / 4 to 1 / 3 of the cross-sectional area of ​​the pin 101. If the cross-sectional area of ​​the through hole 112 or the groove 113 is too large, the strength of the frame connecting rib 110 will be reduced. If the cross-sectional area of ​​the through hole 112 or the groove 113 is too small, the amount of copper chips cannot be effectively improved. The cross-sectional area of ​​the through hole 112 or the groove 113 is 1 / 4 to 1 / 3 of the cross-sectional area of ​​the pin 101, which can take into account both the strength of the frame connecting rib 110 and the reduction of copper chips.

[0046] In some embodiments, the through hole 112 or the groove 113 is disposed on the center line O1 of the substrate 111, and the center line O1 extends along the extension direction of the substrate 111, for example. Figure 1 As shown, the through hole 112 is arranged on the center line O1 of the substrate 111. This arrangement makes the through holes 112 or the grooves 113 evenly distributed between the frame units 100, avoiding the uneven cutting of adjacent frame units 100 in the step cutting process, and improving the consistency of the subsequently formed packaging structure.

[0047] In some embodiments, the surface of the substrate 111 is lower than the surface of the lead 101, which can further reduce the volume of the frame connecting rib 110. For example, the substrate 111 is obtained by half-etching the lead frame substrate, and the thickness of the substrate 111 is half the thickness of the lead 101, and the through hole 112 or the groove 113 is set in the half-etched area.

[0048] In some embodiments, the width of the area where the base 111 is connected to the pin 101 is greater than the width of the area not connected to the pin 101, further improving the support strength of the frame connecting rib 110 for the pin 101 and reducing the volume of the frame connecting rib 110. Figure 2 As shown, it is a cross-sectional view of the area where the substrate 111 is connected to the pin 101, as shown Figure 3 As shown, it is a cross-sectional view of the area where the substrate 111 is not connected to the pin 101 , and the width of the area where the substrate 111 is connected to the pin 101 is greater than the width of the area not connected to the pin 101 .

[0049] In the above embodiments, the substrate 111 has a first width W1, and the microstructure is at least one of a through hole 112 penetrating the substrate 111 or a groove 113 recessed into the substrate 111. In other embodiments, the substrate 111 has a second width W2, and the microstructure is a convex strip 114 arranged on the surface of the substrate 111.

[0050] See also Figure 5 to Figure 7 ,in, Figure 5 is a bottom view of a lead frame provided by a third embodiment of the present invention, Figure 6 is along Figure 5 The cross-sectional view of the A-A1 line, Figure 7 is along Figure 5 In the cross-sectional view along the line B-B1, in this embodiment, the substrate 111 has a second width W2, the second width W2 is less than or equal to the cutting road width, the second width W2 is less than two-thirds of the set width W3 and greater than one-third of the set width W3, the microstructure is a convex strip 114 arranged on the surface of the substrate 111, and the convex strip 114 extends along the extension direction of the substrate 111, and the width of the convex strip 114 is less than the second width W2. The second width W2 of the substrate 111 refers to the width of the substrate 111 in a direction perpendicular to the extension direction of the substrate 111, and the width of the convex strip 114 refers to the width of the convex strip 114 in a direction perpendicular to the extension direction of the substrate 111.

[0051] On the one hand, the second width W2 of the substrate 111 is less than or equal to the cutting path width, so that the substrate 111 is completely located within the cutting path 200. On the other hand, the second width W2 is less than two-thirds of the set width W3. The setting of the second width W2 in this embodiment can reduce the volume of the frame connecting rib 110, thereby reducing or even eliminating the amount of copper chips generated by the first cutting in the step cutting process. In addition, the convex strip 114 is set on the surface of the substrate 111, which can strengthen the strength of the frame connecting rib 110, thereby ensuring the support strength of the frame connecting rib 110 for the pin 101. Figure 6 The cutting street 200 is illustrated by a dotted line.

[0052] In some embodiments, the width of the convex strip 114 is 1 / 3 to 1 / 2 of the second width W2. If the width of the convex strip 114 is too small, the strength of the frame connecting rib 110 will be reduced. If the width of the convex strip 114 is too large, the amount of copper scraps cannot be effectively improved. The width of the convex strip 114 is 1 / 3 to 1 / 2 of the second width W2, which can take into account both the strength of the frame connecting rib 110 and the reduction of copper scraps.

[0053] In some embodiments, the convex strips 114 are arranged on the center line O1 of the substrate 111, and the center line O1 extends along the extension direction of the substrate 111. This arrangement allows the convex strips 114 to be evenly distributed between the frame units 100, thereby avoiding uneven cutting of adjacent frame units 100 in the step cutting process and improving the consistency of the subsequently formed packaging structure.

[0054] In some embodiments, the surface of the substrate 111 is lower than the surface of the pin 101, which can further reduce the volume of the frame connecting rib 110. For example, the substrate 111 is obtained by half-etching the lead frame substrate, and the thickness of the substrate 111 is half the thickness of the pin 101. The convex strip 114 is arranged in the half-etched area, which increases the strength of the frame connecting rib 110.

[0055] In some embodiments, the surface of the convex strip 114 is flush with the surface of the pin 101, or the surface of the convex strip 114 is lower than the surface of the pin 101, so as to provide sufficient support strength while avoiding a significant impact on the structure of the lead frame. Figure 6 As shown, the surface of the convex strip 114 is flush with the surface of the lead 101. In some embodiments, when the lead frame substrate is half-etched to form the frame connecting rib 110, only the area between the convex strip 114 and the lead 101 is half-etched, so that the surface of the convex strip 114 is flush with the surface of the lead 101.

[0056] The lead frame provided by the embodiment of the present invention can reduce or even avoid the generation of abnormal burrs in the packaged product using step cutting by setting the configuration of the microstructure in association with the width of the substrate, thereby improving the yield of the packaged product.

[0057] It should be noted that the terms "including" and "having" and their variations involved in the document of the present invention are intended to cover non-exclusive inclusions. The terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence, unless the context clearly indicates, and it should be understood that the data used in this way can be interchanged under appropriate circumstances. The term "one or more" depends at least in part on the context, and can be used to describe features, structures or characteristics in a singular sense, or can be used to describe features, structures or combinations of features in a plural sense. The term "based on" can be understood as not necessarily intended to express a set of exclusive factors, but can alternatively, also at least in part depending on the context, allow the presence of other factors that are not necessarily explicitly described. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict. In addition, in the above description, the description of well-known components and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. In the above embodiments, each embodiment focuses on the differences from other embodiments, and the same / similar parts between the embodiments can be referred to each other.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A lead frame, characterized in that: include: A frame unit, the frame unit comprising pins; A frame connecting rib is arranged between adjacent frame units, and includes a substrate and a microstructure. The substrate is connected to the pins, and the microstructure is arranged on the substrate. The configuration of the microstructure is associated with the width of the substrate to reduce or even eliminate the amount of copper chips generated when performing a first cut with a set width.

2. The lead frame according to claim 1, characterized in that: The substrate has a first width, which is less than the set width and greater than or equal to two-thirds of the set width. The microstructure is at least one of a through hole passing through the substrate or a groove recessed into the substrate, and the width of the through hole or the groove is less than the first width.

3. The lead frame according to claim 2, characterized in that: The through hole or the groove is arranged between the pins of two adjacent frame units.

4. The lead frame according to claim 2, characterized in that: The through hole or the groove is arranged in an area of ​​the base body that does not correspond to the pin.

5. The lead frame according to claim 2, characterized in that: The cross-sectional area of ​​the through hole or the groove is 1 / 4 to 1 / 3 of the cross-sectional area of ​​the pin.

6. The lead frame according to claim 2, characterized in that: The frame connecting bar comprises a plurality of the through holes or the grooves, and the plurality of the through holes or the grooves are evenly distributed in the extending direction of the base.

7. The lead frame according to claim 2, characterized in that: The through hole or the groove is arranged on the center line of the base.

8. The lead frame according to claim 1, wherein: The substrate has a second width, which is less than two-thirds of the set width and greater than one-third of the set width. The microstructure is a convex strip arranged on the surface of the substrate, and the convex strip extends along the extension direction of the substrate. The width of the convex strip is less than the second width.

9. The lead frame according to claim 8, characterized in that: The width of the convex strip is 1 / 3 to 1 / 2 of the second width.

10. The lead frame according to claim 8, wherein: The surface of the convex strip is flush with the surface of the pin, or the surface of the convex strip is lower than the surface of the pin.

11. The lead frame according to claim 8, wherein: The convex strip is arranged on the center line of the base.

12. The lead frame according to claim 1, wherein: The surface of the base is lower than the surface of the pin.

13. The lead frame according to claim 12, characterized in that The width of the area of ​​the substrate connected to the pin is greater than the width of the area not connected to the pin.

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