TWI834421B - Lead frame structure - Google Patents

Abstract

A lead frame structure includes: a base plate, the base plate includes opposite first and second sides, the base plate includes: a plurality of wafer loading areas; a lead area located around each wafer loading area, the lead area includes a plurality of protrusions There are grooves extending from the first surface to the second surface between adjacent lead parts and between the lead parts and the wafer loading area, and the grooves have the narrowest grooves distributed in a direction perpendicular to the surface of the substrate. The distance between the narrowest part and the first surface of the substrate is smaller than the distance between the widest part and the first surface of the substrate. The structure can improve the reliability of the device after plastic packaging.

Description

Lead frame structure

The invention relates to the field of semiconductor packaging, and in particular to a lead frame structure.

This application claims priority to the Chinese patent application filed with the China Patent Office on December 17, 2021, with the application number 202111550500.9 and the invention name " Lead Frame Structure ", the entire content of which is incorporated into the present invention by reference.

In recent years, as the size and volume of semiconductor devices have continued to become miniaturized, the packaging requirements in the latter part of the semiconductor process have become increasingly higher. In order to meet such requirements, various Quad Flat No-leads Package (QFN) type semiconductor devices have been proposed, which use a lead frame and seal the semiconductor element mounted on its mounting surface with a sealing resin. , while leaving part of the lead exposed on the back.

Existing packaging processes still need to be continuously improved to meet higher requirements.

The technical problem solved by the present invention is to provide a lead frame structure to meet higher requirements of packaging technology.

In order to solve the above technical problems, the technical solution of the present invention provides a lead frame structure, including: a substrate, the substrate includes an opposite first side and a second side, the substrate includes: a plurality of wafer loading areas; located around each wafer loading area The lead area includes a plurality of protruding lead portions, with grooves extending from the first surface to the second surface between adjacent lead portions and between the lead portions and the wafer loading area, and the grooves have The narrowest part and the widest part distributed in the direction perpendicular to the substrate surface, the distance between the narrowest part and the first surface of the substrate is smaller than the distance between the widest part and the first surface of the substrate spacing.

Optionally, the groove includes a first subpart and a second subpart located at the bottom of the first subpart, the top of the second subpart is connected with the bottom of the first subpart, and the second subpart The side wall surface is a concave surface.

Optionally, the narrowest part is the bottom of the first subsection and the top of the second subsection, and the top of the first subsection in the first direction and the second direction parallel to the surface of the lead frame has a first size, the narrowest part has a second size in the first direction and the second direction, the largest size of the widest part in the first direction and the second direction is a third size, the first direction and the second direction The two directions are perpendicular, the first dimension is larger than the second dimension, and the second dimension is smaller than the third dimension.

Optionally, the bottom surface of the second part is a concave surface, or the bottom surface of the second part is a plane.

Optionally, the cross-section of the groove in a direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the range in which the third dimension is larger than the second dimension on one side is greater than 10 microns.

Optionally, the groove further includes: a third subsection located at the bottom of the second subsection, the top of the third subsection is connected with the bottom of the second subsection, and the side wall surface of the third subsection is a concave surface.

Optionally, the bottom of the second subsection in the first direction and the second direction and the top of the third subsection in the first direction and the second direction have a fourth size, and the third subsection has a fourth size in the first direction and the second direction. The largest dimension in one direction is the third dimension of the widest part, the fourth dimension is smaller than the third dimension, and the fourth dimension is larger than the second dimension.

Optionally, the cross-section of the groove in a direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the range in which the third dimension is larger than the fourth dimension on one side is greater than 10 microns.

Optionally, the bottom surface of the third part is a concave surface, or the bottom surface of the third part is a plane.

Optionally, the projection pattern of the wafer loading area on the surface of the substrate is a rectangle.

Optionally, the lead area includes several circle areas, and several circles of the sub-areas are concentrically distributed around the wafer loading area. There are several mutually separated lead parts in any circle area.

Optionally, the central axes of two adjacent turns of the lead portion do not overlap.

Optionally, the substrate further includes a plurality of through holes penetrating from the first surface to the second surface of the substrate, and the through holes are located between part of the lead areas, or the through holes are located between part of the wafer loading area and the lead area. between.

Optionally, the base plate further includes: a plurality of openings extending from the second surface to the first surface and connected with the groove.

Optionally, the material of the substrate includes metal, and the metal includes copper, copper alloy, or iron-nickel alloy with a nickel content of 42%.

Optionally, the size range of the center points of adjacent lead portions between the first direction or the second direction is greater than or equal to 0.4 mm.

Optionally, the size range of the narrowest part of the groove is greater than or equal to 0.1 mm; the depth of the groove is 50% to 70% of the thickness of the substrate.

Compared with the existing technology, the technical solution of the present invention has the following beneficial effects:

According to the technical solution of the present invention, the lead frame structure has grooves extending from the first surface to the second surface between adjacent lead portions and between the lead portions and the wafer loading area, and the grooves have a direction perpendicular to the substrate surface. The narrowest part and the widest part are distributed in the direction, and the distance between the narrowest part and the first surface of the substrate is smaller than the distance between the widest part and the first surface of the substrate. Therefore, the size of the groove in the direction perpendicular to the surface of the lead frame changes irregularly, so that the molding material and the groove filled into the groove during subsequent molding can achieve a physical blocking structure, improving the The bonding force between the plastic packaging material and the groove sidewall can improve the reliability of the device after plastic packaging.

Further, the groove includes a first portion and a second portion located at the bottom of the first portion, the top of the first portion having a first size in a first direction parallel to the surface of the lead frame, the The bottom of the first portion in the first direction and the top of the second portion in the first direction have a second dimension. size, the maximum size of the second portion in the first direction is a third size, the first size is larger than the second size, and the second size is smaller than the third size. The second size is smaller than the third size, so that the plastic packaging material and the groove subsequently filled into the groove can achieve a physical snap-in structure, improve the bonding force between the plastic packaging material and the side wall of the groove, and improve the strength of the device after plastic packaging. reliability.

100: Lead frame

101,205: Groove

102:Chip

103:Lead

104:Plastic sealing layer

200:Substrate

201: First side

202:Second side

204: Lead part

206,306,406,506: Division 1

207,307,407,507:Second Division

408,508: Division 3

620,720:Open

AA1,BB1: direction

d1: first size

d2: second size

d3: third dimension

d4: fourth dimension

I:wafer loading area

II: Sub-area

X: first direction

Y: second direction

Figures 1 and 2 are schematic cross-sectional structural diagrams of the packaging structure formation process in one embodiment;

3 to 5 are schematic diagrams of the lead frame structure in an embodiment of the present invention;

Figure 6 is a schematic diagram of a lead frame structure in another embodiment of the present invention;

Figure 7 is a schematic diagram of a lead frame structure in another embodiment of the present invention;

Figure 8 is a schematic diagram of a lead frame structure in another embodiment of the present invention;

Figure 9 is a schematic diagram of a lead frame structure in another embodiment of the present invention;

Figure 10 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

As mentioned in the prior art, existing packaging processes still need to be continuously improved to meet higher requirements. Analysis and description will now be carried out with reference to specific examples.

1 and 2 are schematic cross-sectional structural diagrams of the packaging structure forming process in one embodiment.

Referring to FIG. 1 , a lead frame 100 is provided. The lead frame 100 includes a pad area (not labeled), a lead portion (not labeled), and a groove 101 between the pad area and the lead portion; a chip 102 is provided. The chip 102 is fixed on the pad area; leads 103 are provided, and the leads are electrically connected to the chip 102 and the lead portion.

Please refer to FIG. 2 , a plastic sealing layer 104 is formed on the lead frame 100 , the chip 102 and the leads 103 are located in the plastic sealing layer 104 , and the plastic sealing layer 104 is also located in the groove 101 .

In the packaging structure, the plastic sealing layer 104 is located in the groove 101, so that the The contact area between the plastic layer 104 and the lead frame 100 becomes larger, thereby increasing the bonding force between the plastic layer 104 and the lead frame 100 , which is beneficial to improving the reliability of the packaging structure.

However, since the groove 101 is a bowl-shaped structure with a wide top and a narrow bottom, the plastic sealing layer 104 and the lead frame 100 are completely bonded by surface bonding force. When encountering temperature changes or external forces, plastic sealing can easily occur. Delamination of layer 104 from lead frame 100 results in wafer failure.

In order to solve the above problems, the technical solution of the present invention provides a lead frame structure. The lead frame structure has grooves extending from the first surface to the second surface between adjacent lead parts and between the lead parts and the chip loading area. The groove has a narrowest part and a widest part distributed in a direction perpendicular to the surface of the substrate, and the distance between the narrowest part and the first surface of the substrate is smaller than the distance between the widest part and the first surface of the substrate. spacing. Therefore, the size of the groove in the direction perpendicular to the surface of the lead frame changes irregularly, so that the molding material and the groove filled into the groove during subsequent molding can achieve a physical blocking structure, improving the The bonding force between the plastic packaging material and the groove sidewall can improve the reliability of the device after plastic packaging.

In order to make the above objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention will be described in detail below in conjunction with the drawings.

3 to 5 are schematic diagrams of a lead frame structure in an embodiment of the present invention.

Please refer to Figures 3 to 5. Figure 3 is a top view of Figures 4 and 5. Figure 4 is a schematic structural view of Figure 3 along the section line AA1. Figure 5 is a schematic structural view of Figure 3 along the section line BB1. The leads Box structure, including:

The substrate 200 includes an opposite first side 201 and a second side 202. The substrate 200 includes:

several wafer loading areas I;

A lead area located around each wafer loading area I. The lead area includes a plurality of protruding lead portions 204. Between adjacent lead portions 204, and between the lead portions 204 and the wafer loading area I, there is a line extending from the first surface 201 to the wafer loading area I. A groove 205 extends from the second surface 202 . The groove 205 has a surface along a direction perpendicular to the surface of the substrate 200 . The narrowest part and the widest part are distributed in the surface direction, and the distance between the narrowest part and the first surface 201 of the substrate 200 is smaller than the distance between the widest part and the first surface 201 of the substrate 200 .

The lead frame structure has a groove 205 extending from the first surface 201 to the second surface 202 between adjacent lead portions 204 and between the lead portion 204 and the wafer loading area 1. The groove 205 has an edge perpendicular to The narrowest part and the widest part distributed in the surface direction of the substrate 200. The distance between the narrowest part and the first surface 201 of the substrate 200 is smaller than the distance between the widest part and the first surface 201 of the substrate 200. . Therefore, the size of the groove 205 in the direction perpendicular to the surface of the lead frame changes irregularly, so that the molding material filled into the groove 205 and the groove 205 during subsequent molding can achieve physical blocking. The structure improves the bonding force between the plastic packaging material and the side wall of the groove 205, which can improve the reliability of the device after plastic packaging.

In this embodiment, the material of the substrate 200 includes metal, and the metal includes copper, copper alloy, or iron-nickel alloy (42 alloy) with a nickel content of 42%.

In this embodiment, the size range of the center points of adjacent lead portions 204 between the first direction X or the second direction Y is greater than or equal to 0.4 mm.

In other embodiments, the substrate further includes a plurality of through holes penetrating from the first surface to the second surface of the substrate, and the through holes are located between part of the lead areas, or the through holes are located between part of the wafer loading area and the lead areas. between districts.

Please continue to refer to FIGS. 3 to 5 . In this embodiment, the projection pattern of the wafer loading area I on the surface of the substrate 200 is a rectangle.

In this embodiment, the lead area includes several circle areas II, and several circles of the sub-areas II are concentrically distributed around the wafer loading area I. There are several mutually separated lead parts 204 in any circle area II.

In this embodiment, the central axes of the lead portions 204 in two adjacent circle areas II do not overlap. In order to subsequently implement multi-layer wiring between the wiring portion 204 and the wafer loading area 1.

Please continue to refer to Figures 3 to 5. In this embodiment, the groove 205 includes a third A subsection 206 and a second subsection 207 located at the bottom of the first subsection 206. The top of the second subsection 207 is connected with the bottom of the first subsection 206. The side wall surface of the second subsection 207 is Concave surface.

The narrowest part is the bottom of the first subsection 206 and the top of the second subsection 207. The top of the first subsection 206 in the first direction X and the second direction Y parallel to the surface of the lead frame has a A dimension d1, the narrowest part has a second dimension d2 in the first direction X and the second direction Y, and the maximum dimension of the widest part in the first direction X and the second direction Y is a third dimension d3 , the first dimension d1 is larger than the second dimension d2, the second dimension d2 is smaller than the third dimension d3, and the first direction X and the second direction Y are perpendicular to each other.

Therefore, the size of the groove 205 in the direction perpendicular to the surface of the lead frame changes irregularly, the first size d1 is larger than the second size d2, and the second size d2 is smaller than the third size d3. This enables the plastic sealing material filled into the groove 205 to be subsequently filled into the groove 205 and the narrowest part of the groove 205 to achieve a physical snap-in structure, thereby improving the bonding force between the molding material and the side wall of the groove 205 and improving the device after molding. reliability.

In this embodiment, the bottom surface of the second portion 207 is a concave surface.

In other embodiments, the bottom surface of the second portion is planar.

In this embodiment, the cross section of the groove 205 in the direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the range in which the third dimension d3 is greater than the second dimension d2 on one side is greater than 10 microns. In order to ensure that the plastic sealing material subsequently filled into the groove 205, the plastic sealing material located in the second part 207 and the narrowest part of the groove 205 can achieve a physical snap-in structure, thereby improving the plastic sealing material and the side wall of the groove 205. the binding force.

In this embodiment, the size range of the narrowest part of the groove 205 is greater than or equal to 0.1 mm; the depth of the groove 205 is 50% to 70% of the thickness of the substrate.

FIG. 6 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

Please refer to Figure 6, which is a schematic structural diagram consistent with the perspective of Figure 4. In this embodiment, the groove 205 includes a first sub-section 306 and a second sub-section located at the bottom of the first sub-section 306. 307. The top of the second subsection 307 is connected with the bottom of the first subsection 306, and the side wall surface of the second subsection 307 is a concave surface.

The difference between the structure shown in Figure 6 and the structure shown in Figure 4 is that the bottom surface of the second portion 307 is flat.

FIG. 7 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

Please refer to Figure 7, which is a schematic structural diagram consistent with the perspective of Figure 4. In this embodiment, the groove 205 includes a first subsection 406 and a second subsection 407 located at the bottom of the first subsection 406, so The top of the second subpart 407 is connected with the bottom of the first subpart 406, and the side wall surface of the second subpart 407 is a concave surface.

In this embodiment, the groove 205 further includes: a third subsection 408 located at the bottom of the second subsection 407. The top of the third subsection 408 is connected with the bottom of the second subsection 407. The sidewall surface of the third segment 408 is a concave surface.

The narrowest part is the bottom of the first subsection 406 and the top of the second subsection 407. The top of the first subsection 406 in the first direction X and the second direction Y parallel to the surface of the lead frame has a A dimension d1, the narrowest part has a second dimension d2 in the first direction X and the second direction Y, and the maximum dimension of the widest part in the first direction X and the second direction Y is a third dimension d3 , the first dimension d1 is larger than the second dimension d2, and the second dimension d2 is smaller than the third dimension d3.

The bottom of the second sub-portion 407 in the first direction X and the second direction Y and the top of the third sub-portion 408 in the first direction X and the second direction Y have a fourth dimension d4. The maximum dimension of the portion 408 in the first direction is the third dimension d3 of the widest portion, the fourth dimension d4 is smaller than the third dimension d3, and the fourth dimension d4 is larger than the second dimension d2.

The size of the groove 205 in the direction perpendicular to the surface of the lead frame changes irregularly, the first size d1 is larger than the second size d2, the second size d2 is smaller than the third size d3, and the fourth size d3 is smaller than the third size d3. Dimension d4 is smaller than the third dimension d3, which is larger than the second dimension d2. This enables the plastic sealing material filled into the groove 205 and the narrowest part of the groove 205 to achieve a physical snap-in structure during subsequent sealing, thereby improving the bonding force between the plastic sealing material and the side wall of the groove 205 and improving the plastic sealing ability. the reliability of the final device.

In this embodiment, the cross section of the groove 205 in the direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the range in which the third dimension d3 is larger than the fourth dimension d4 on one side is greater than 10 microns.

In this embodiment, the bottom surface of the third portion 408 of the groove 205 is a concave surface.

In other embodiments, the bottom surface of the third portion is planar.

FIG. 8 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

Please refer to Figure 8. Figure 8 is a schematic structural diagram consistent with the perspective of Figure 7. In this embodiment, the groove 205 includes a first subsection 506 and a second subsection 507 located at the bottom of the first subsection 506. The top of the second part 507 is connected with the bottom of the first part 506, and the side wall surface of the second part 507 is a concave surface; the groove 205 also includes a third part located at the bottom of the second part 507. Part 508, the top of the third part 508 is connected with the bottom of the second part 507, and the side wall surface of the third part 508 is a concave surface.

The difference between the structure shown in Figure 8 and the structure shown in Figure 7 is that the bottom surface of the third portion 508 is flat.

FIG. 9 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

Please refer to Figure 9. Figure 9 is a schematic structural diagram based on Figure 4. The difference between the structure of Figure 9 and the structure of Figure 4 is that the substrate 200 also includes: a number of extending from the second surface 202 to the first surface 201 and connected with the first surface 201. The groove 205 communicates with the opening 620 .

The opening 620 is connected to the bottom of the groove 205, so that the subsequent molding material can be filled into the opening 620. When multi-layer leads are subsequently implemented between the lead portion 204 and the wafer loading area 1, the molding material located in the opening 620 plays a role. Further isolation is beneficial to achieve multi-layer leads.

Figure 10 is a schematic diagram of a lead frame structure in another embodiment of the present invention.

Please refer to Figure 10. Figure 10 is a schematic structural diagram based on Figure 7. The difference between the structure of Figure 10 and the structure of Figure 7 is that the substrate 200 also includes: a number of extending from the second surface 202 to the first surface 201 and connected with the first surface 201. The groove 205 communicates with the opening 720 .

The opening 720 is connected to the bottom of the groove 205, so that the subsequent molding material can be filled into the opening 720. When multi-layer leads are subsequently implemented between the lead portion 204 and the wafer loading area 1, the molding material located in the opening 720 plays a role. Further isolation is beneficial to achieve multi-layer leads.

Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

200:Substrate

201: First side

202:Second side

204: Lead part

205: Groove

206:First Division

207:Second Division

d1: first size

d2: second size

d3: third dimension

Y: second direction

Claims (11)

A lead frame structure, characterized in that it includes: a base plate, the base plate includes an opposite first surface and a second surface, the base plate includes: a plurality of wafer loading areas; a lead area located around each wafer loading area, the lead The area includes a plurality of protruding lead parts, and between adjacent lead parts and between the lead parts and the wafer loading area, there is a groove extending from the first surface to the second surface, the groove having a direction perpendicular to the substrate surface. The narrowest part and the widest part of the distribution, the distance between the narrowest part and the first surface of the substrate is smaller than the distance between the widest part and the first surface of the substrate, the groove includes a first part part, a second part located at the bottom of the first part and a third part located at the bottom of the second part, and the top of the second part is connected to the bottom of the first part, The top of the third division is connected with the bottom of the second division, the side wall surface of the second division is a concave surface, the side wall surface of the third division is a concave surface, and the first The top of the portion has a first size in the first direction and the second direction parallel to the surface of the lead frame, the narrowest portion is the bottom of the first portion and the top of the second portion, and the The narrowest part has a second dimension in the first direction and the second direction, the maximum dimension of the third sub-part in the first direction is the third dimension of the widest part, and the second sub-part is in the first direction. The bottom in the first direction and the second direction and the top of the third portion in the first direction and the second direction have a fourth dimension, the first direction and the second direction are perpendicular, and the first dimension is greater than a second size, the second size is smaller than the third size, the fourth size is smaller than the third size, the fourth size is larger than the second size, the bottom surface of the third segment is a concave surface, or the The bottom surface of the third segment is flat. The lead frame structure according to claim 1, wherein the cross-section of the groove in the direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the range in which the third dimension is larger than the second dimension on one side is greater than 10 microns. . The lead frame structure according to claim 1, wherein the cross section of the groove in the direction perpendicular to the surface of the lead frame is an axially symmetrical figure, and the third dimension is larger than the fourth dimension on one side. The range is greater than 10 microns. The lead frame structure according to claim 1, wherein the projection pattern of the wafer loading area on the surface of the substrate is a rectangle. The lead frame structure according to claim 4, wherein the lead area includes a plurality of circle areas, a plurality of circles of the sub-areas are concentrically distributed around the wafer loading area, and any circle area has a number of mutually independent lead parts. The lead frame structure as claimed in claim 5, wherein the central axes of two adjacent turns of the lead portion do not overlap. The lead frame structure according to claim 1, wherein the substrate further includes a plurality of through holes penetrating from the first surface to the second surface of the substrate, and the through holes are located between some of the lead regions, or the through holes Located between part of the wafer loading area and the lead area. The lead frame structure according to claim 1, wherein the substrate further includes: a plurality of openings extending from the second surface to the first surface and connected with the groove. The lead frame structure according to claim 1, wherein the material of the substrate includes metal, and the metal includes copper, copper alloy or iron-nickel alloy with a nickel content of 42%. The lead frame structure according to claim 1, wherein the size range between the center points of adjacent lead portions in the first direction or the second direction is greater than or equal to 0.4 mm. The lead frame structure according to claim 1, wherein the size range of the narrowest part of the groove is greater than or equal to 0.1 mm; the depth of the groove is 50% to 70% of the thickness of the substrate.

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