CN119208282A - Lead frame structure and packaging structure thereof - Google Patents

Abstract

The lead frame structure comprises a base island and pins, wherein the pins are arranged at intervals with the base island, the back surfaces of the pins are provided with entities, the number of the entities on the same pin is one or more, and the back surfaces of the pins face away from a device bearing surface of the base island. The entity of the embodiment of the invention can play a supporting role on the pins, reduces the probability of deformation caused by insufficient supporting force of the pins, and correspondingly improves the deformation resistance of the lead frame structure, thereby being beneficial to improving the covering capacity of plastic packaging materials on the pins in the subsequent plastic packaging process, reducing the probability of exposing unexpected areas in the pins, and further improving the yield of the packaging structure.

Description

Lead frame structure and packaging structure thereof

Technical Field

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

Background

In recent years, the high-speed development of electronic technology has increased the demand for reliability in semiconductor packages. In the packaging process of the semiconductor chip, the lead frame is required to be used for realizing the electrical connection between the semiconductor chip and an external circuit so as to realize the electrical function executed by the semiconductor chip, and in addition, the lead frame can also provide physical support for the semiconductor chip.

The lead frame is a key structural member for realizing the electric connection between the lead-out end of the internal circuit of the chip and the external circuit to form an electric loop, and plays a role of a bridge connected with the external circuit, and most of semiconductor integrated blocks need to use the lead frame, so the lead frame is an important basic material in the electronic information industry.

At present, the lead frame structure and the package structure are still to be improved.

Disclosure of Invention

The embodiment of the invention provides a lead frame structure and a packaging structure thereof, which are used for improving the performance of the packaging structure.

In order to solve the problems, the embodiment of the invention provides a lead frame structure, which comprises a base island and pins, wherein the pins are arranged at intervals with the base island, the back surfaces of the pins are provided with one or more entities, and the back surfaces of the pins face away from a device bearing surface of the base island.

Optionally, the lead frame structure comprises a frame unit, wherein the frame unit comprises the base island and pins, the frame unit further comprises connecting ribs for connecting the base island and the top corners of the frame unit, the connecting ribs and the pins are mutually spaced, and the entity is positioned on the pins close to the connecting ribs.

Optionally, the lead frame structure comprises a frame unit, wherein the frame unit comprises the base island and the pins, the frame unit further comprises connecting ribs for connecting the base island and the top corners of the frame unit, the connecting ribs and the pins are mutually spaced, and entities on the adjacent pins are staggered on any side of the connecting ribs.

Optionally, the number of pins is plural on either side of the connection bar, and the layout of the entities on the plural pins includes that the positions of the entities on different pins are progressive toward the base island.

Optionally, the entity and the pin are in an integrated structure, or the entity is welded on the back surface of the pin, or the entity is adhered on the back surface of the pin.

Optionally, the pins include an inner pin and an outer pin that are connected, and the outer pin is located at an end of the inner pin away from the base island, and the entity is disposed on the inner pin.

Optionally, the back of the pin is provided with a step, and the pin comprises an inner pin positioned at the concave position of the step and an outer pin connected with the inner pin.

Optionally, on the back side of the pin, the bottom of the outer pin is flush with the bottom of the solid body.

Optionally, the width of the entity is smaller than or equal to the width of the inner pin.

Optionally, the ratio of the length to the width of the entity is greater than or equal to 2.

Optionally, the length of the entity is less than or equal to 1/2 of the length of the pin where the entity is located.

Optionally, the shortest distance between adjacent entities located on different pins is greater than or equal to 1.5 times the pitch of adjacent pins.

Optionally, when the number of entities located on the same pin is plural, the distance between the entities on the same pin is greater than or equal to the width of the pin where the entities are located.

Optionally, the solid material comprises one or more of tungsten, aluminum, copper, titanium, silver, gold, platinum, nickel, iron, and alloys thereof.

Correspondingly, the embodiment of the invention also provides a packaging structure which comprises the lead frame structure according to any embodiment of the invention, a chip which is arranged on the device bearing surface of the base island and is electrically connected with the pins, and a plastic packaging material for plastic packaging the lead frame structure and the chip.

Optionally, the pins include an inner pin and an outer pin which are connected, the outer pin is located at one end of the inner pin away from the base island, the entity is arranged on the inner pin, and the plastic package material exposes the bottom of the outer pin.

Optionally, the molding compound exposes the bottom of the entity.

Optionally, the packaging structure further comprises a solder wetting layer positioned at the bottom of the outer pin and the solid bottom exposed to the plastic packaging material.

Optionally, the thickness of the solder wetting layer ranges from 8 micrometers to 15 micrometers.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

the lead frame structure provided by the embodiment of the invention comprises the base islands and the pins which are arranged at intervals, wherein the back surfaces of the pins are provided with the entities, the entities can play a supporting role on the pins, the probability of deformation caused by insufficient supporting force of the pins is reduced, and correspondingly the deformation resistance of the lead frame structure is improved, so that the covering capacity of plastic packaging materials on the pins in the subsequent plastic packaging process is improved, the probability of exposing unexpected areas in the pins is reduced, and the yield of the packaging structure is improved.

Drawings

Fig. 1 is a schematic view of a lead frame structure;

FIG. 2 is an enlarged view of a portion of FIG. 1 at area A;

FIG. 3 is a schematic diagram of a package structure with the backside of the leads exposed;

FIG. 4 is a schematic diagram of an embodiment of a leadframe structure according to the present invention;

FIG. 5 (a) is an enlarged partial view of the first embodiment of FIG. 4 at region B;

FIG. 5 (B) is an enlarged partial view of the second embodiment of FIG. 4 at region B;

FIG. 5 (c) is an enlarged partial view of the third embodiment of FIG. 4 at region B;

FIG. 5 (d) is an enlarged partial view of the fourth embodiment of FIG. 4 at region B;

FIG. 5 (e) is an enlarged partial view of the fifth embodiment of FIG. 4 at region B;

FIG. 6 is a cross-sectional view of FIG. 4 at CC 1;

Fig. 7 is a schematic cross-sectional view of an embodiment of the package structure of the present invention.

Detailed Description

At present, the lead frame structure and the package structure are still to be improved. The lead frame structure and the packaging structure are combined, and the reasons for the lead frame structure and the packaging structure are still to be improved. Fig. 1 is a schematic view of a lead frame structure, fig. 2 is a partial enlarged view of a region a of fig. 1, and fig. 3 is a schematic view of a package structure in a case where a back surface of a lead is exposed.

Referring to fig. 1-2, a lead frame structure 20 includes a base island 21 and a lead 22, the lead 22 being spaced from each other between the base island 21 and between adjacent leads 22.

The leadframe structure 20 is typically subjected to a lamination process prior to injection molding the package. However, it has been found that the lead frame structure 20 with a larger area easily causes insufficient supporting force of the leads 22, so that the leads 22 of the lead frame structure 20 are easily deformed during the film pasting process, so that the leads 22 at the deformed position cannot be completely covered by the molding compound and are exposed from the molding compound (as shown in a dashed line frame in fig. 3), namely, a defect of "finger leakage" is generated, and the yield of the packaging structure is further affected.

In order to solve the technical problems, the embodiment of the invention provides a lead frame structure, which comprises a base island and pins, wherein the pins are arranged at intervals with the base island, the back surfaces of the pins are provided with one or more entities, and the back surfaces of the pins are opposite to a device bearing surface of the base island.

The lead frame structure provided by the embodiment of the invention comprises the base islands and the pins which are arranged at intervals, wherein the back surfaces of the pins are provided with the entities, the entities can play a supporting role on the pins, the probability of deformation caused by insufficient supporting force of the pins is reduced, and correspondingly the deformation resistance of the lead frame structure is improved, so that the covering capacity of plastic packaging materials on the pins in the subsequent plastic packaging process is improved, the probability of exposing unexpected areas in the pins is reduced, and the yield of the packaging structure is improved.

In order that the above objects, features and advantages of embodiments of the invention may be readily understood, a more particular description of embodiments of the invention will be rendered by reference to the appended drawings.

Fig. 4 is a schematic structural view of an embodiment of the lead frame structure of the present invention, fig. 5 (a) is a partially enlarged view of the first embodiment of fig. 4 in the B region, fig. 5 (B) is a partially enlarged view of the second embodiment of fig. 4 in the B region, fig. 5 (c) is a partially enlarged view of the third embodiment of fig. 4 in the B region, fig. 5 (d) is a partially enlarged view of the fourth embodiment of fig. 4 in the B region, and fig. 6 is a cross-sectional view of fig. 4 at CC 1.

Referring to fig. 4 to 6, in the present embodiment, the leadframe structure 100 includes a base island 110, and pins 120 spaced from the base island 110, wherein the back surfaces 125 (as shown in fig. 6) of the pins 120 are provided with entities 130, the number of the entities 130 on the same pin 120 is one or more, and the back surfaces 125 of the pins 120 face away from the device carrying surface 115 (as shown in fig. 6) of the base island 110.

The leadframe structure 100 is used to carry a chip and to make electrical connections between the chip and external circuitry.

In this embodiment, the leadframe structure 100 is used to prepare leadless packages, including but not limited to Quad Flat No-leads (QFN) packages.

In this embodiment, the material of the leadframe structure 100 is a metal or an alloy. As an example, the material of the leadframe structure 100 may be one or more of tungsten, aluminum, copper, titanium, silver, gold, platinum, nickel, iron, and alloys thereof. As an example, the material of the leadframe structure 100 is copper or iron-nickel alloy.

In this embodiment, the leadframe structure 100 includes a frame unit 101, and the frame unit 101 includes the base island 110 and the leads 120.

The frame unit 101 is used as a basic unit constituting the lead frame structure 100.

As one illustration, only one frame unit 101 is schematically shown in the present embodiment. The leadframe structure 100 may include a plurality of frame cells 101.

The frame unit 101 has a polygonal shape. In this embodiment, the frame unit 101 has a square shape. As an example, the shape of the frame unit 101 is square.

Thus, the frame unit 101 has top corners, for example, a square frame unit 101 has four top corners.

In other embodiments, the shape of the frame element may be other suitable shapes.

The base island 110 is used as a platform for carrying chips. Correspondingly, the base island 110 has a device carrying surface 115, and the device carrying surface 115 of the base island 110 is used for placing a chip.

The shape of the base island 110 is polygonal. In this embodiment, the shape of the base island 110 is square. As an example, the shape of the base island 110 is square.

Thus, the islands 110 have top corners, e.g., square islands 110 have four top corners.

In other embodiments, the shape of the islands may be other shapes as appropriate.

One end of the pin 120 is used for being electrically connected with a chip, and the other end of the pin 120 is used for being electrically connected with an external circuit.

It should be noted that the number of the pins 120 may be one or more. In this embodiment, the number of the pins 120 is plural, and correspondingly, adjacent pins 120 are spaced apart from each other.

In this embodiment, a plurality of the pins 120 are distributed around the island 110.

In this embodiment, the pins 120 include an inner pin 121 and an outer pin 122 connected to each other, and the outer pin 122 is located at an end of the inner pin 121 away from the base island 110.

The inner pins 121 are used for electrically connecting with a chip and for connecting the outer pins 122 with the entity 130.

The outer pins 122 serve as lead pads (pads) for electrical connection with external circuitry. In particular, the outer leads 122 are typically used for soldering to a substrate (e.g., a PCB board).

The outer leads 122 are located at the end of the inner leads 121 away from the base island 110, which is advantageous for increasing the distance between the adjacent outer leads 122, thereby reducing the probability of short-circuiting between the adjacent outer leads 122.

In this embodiment, the back surface 125 of the lead 120 has a step, the lead 120 includes an inner lead 121 located at a recessed position of the step, and an outer lead 122 connected to the inner lead 121, so that in a subsequent plastic packaging process, the plastic packaging material covers the inner lead 121 and exposes the bottom 126 of the outer lead 122, and the bonding strength between the plastic packaging material and the lead 120 is increased.

In this embodiment, the frame unit 101 further includes a connecting rib 140 for connecting the base island 110 and the top corner of the frame unit 101, where the connecting rib 140 is spaced from the lead 120.

The connection ribs 140 are used to connect the base island 110 to the top corners of the frame unit 101 to fix the base island 110.

In this embodiment, the shape of the base island 110 is square, and the base island 110 also has a vertex angle, so that the connecting ribs 140 connect the base island 110 and the oppositely disposed vertex angle of the frame unit 101. For example, the ribs 140 may extend in a diagonal direction of the frame unit 101.

It should be noted that, the frame unit 101 and the base island 110 are generally square and concentrically arranged, and in order to facilitate the arrangement of the pins 120, the connection ribs 140 are generally located at diagonal positions of the frame unit 101.

It will be appreciated that since the apex angle of the frame unit 101 is furthest from the base island 110, the length of the leads 120 adjacent to the tie bars 140 is correspondingly greater than the length of the leads 120 remote from the tie bars 140, i.e., the length of the leads 120 immediately adjacent to the tie bars 140 is greatest.

As an example, the four corners of the base island 110 are connected to the respective corners of the frame unit 101 by four connection bars 140.

In this embodiment, the frame unit 101 further includes a rim 150 located at an edge position of the frame unit 101, the rim 150 surrounds the pins 120 and the islands 110, and the rim 150 connects the pins 120 along a circumferential direction of the frame unit 101.

Accordingly, the tie bars 140 connect the base islands 110 to the side bars 150 at the top corner positions of the frame units 101.

In fig. 6, the ribs are omitted for clarity of illustration of the lead frame structure.

The ribs 150 serve to fix the pins 120 and the connecting ribs 140 before plastic encapsulation.

When the lead frame structure 100 includes a plurality of frame units 101, adjacent frame units 101 may share the same rim 150.

It should be noted that, after the lead frame structure 100 and the chip are encapsulated by the molding compound, the rim 150 needs to be cut and removed to separate the leads 120 from each other and separate the adjacent leads 120 from the connecting ribs 140.

The entity 130 can support the pins 120, so that the probability of deformation caused by insufficient supporting force of the pins 120 is reduced, and the deformation resistance of the lead frame structure 100 is correspondingly improved, thereby being beneficial to improving the covering capacity of plastic packaging materials on the pins 120 in the subsequent plastic packaging process, reducing the probability of exposing unexpected areas in the pins 120, and further improving the yield of the packaging structure.

In this embodiment, the entity 130 is disposed on the back surface 125 of the lead 120, and the back surface 125 of the lead 120 refers to a surface of the lead 120 opposite to the device carrying surface 115 of the base island 110.

In this embodiment, the pins 120 include an inner pin 121 and an outer pin 122 that are connected, the outer pin 122 is a portion to be exposed in the pins 120, and the inner pin 121 is a portion to be plastic-sealed in the pins 120, so that the entity 130 is disposed on the inner pin 121 to support the inner pin 121, thereby reducing the probability of exposing the inner pin 121.

Specifically, the back surface 125 of the lead 120 has a step, and the lead 120 includes the inner lead 121 located at a concave position of the step, in other words, the thickness of the inner lead 121 is smaller or the length of the inner lead 121 is longer, and the inner lead 121 is more easily deformed, so that the entity 130 is disposed on the inner lead 121, which is easier to satisfy the thickness and length requirements of the inner lead 121, thereby meeting the size requirements of the package structure formed by the frame unit 101. For example, as the size of the leadless package increases, the length of the required leads 120 increases, and by providing the entity 130, the use of longer inner leads 121 is facilitated.

The number of entities 130 on the same pin 120 may be one or more.

In some embodiments, the number of entities 130 on the same pin 120 is one, as shown in fig. 5 (a), 5 (b), or 5 (c), and in other embodiments, the number of entities 130 on the same pin 120 may be multiple, as shown in fig. 5 (d) or 5 (e).

In order to enable the entities 130 to perform a better supporting effect on the pins 120, the number of entities 130 on the same pin 120 may be determined according to the length of the pin 120, i.e. when the length value of the pin 120 is smaller, one entity 130 is provided on the back surface 125 of the same pin 120, and when the length value of the pin 120 is larger, a plurality of entities 130 are provided on the back surface 125 of the same pin 120. For example, when the length value of the pins 120 is large, two entities 130 are disposed on the back surface 125 of the same pin 120, i.e., the number of entities 130 is selected appropriately according to the length of the pins 120. It is understood that the number of entities 130 on the back 125 of the same pin 120 is not limited to two, but may be three, four, etc.

It should be noted that, when the number of entities 130 on the same pin 120 is plural, the distance between the entities 130 on the same pin 120 should not be too small. If the spacing between the entities 130 on the same pin 120 is too small, the difficulty of forming the entities 130 is easily increased. Therefore, in the present embodiment, when the number of the entities 130 on the same pin 120 is plural, the distance between the entities 130 on the same pin 120 is greater than or equal to the width of the pin 120 where the entities 130 are located.

In this embodiment, the entity 130 is located on the pin 120 near the connecting rib 140.

Compared with the short pins, the problem of insufficient supporting force of the long pins is particularly remarkable, the long pins are easier to deform, and the length of the pins 120 adjacent to the connecting ribs 140 is the largest, so that the entity 130 can better exert the effect of improving the phenomenon of insufficient supporting force of the pins 120 when the entity 130 is arranged on the pins 120 close to the connecting ribs 140.

In this embodiment, the layout of the entities 130 on the plurality of pins 120 on either side of the connecting rib 140 includes staggering the entities 130 on adjacent pins 120.

On either side of the connecting rib 140, the entities 130 on the adjacent pins 120 are staggered, which is beneficial to increasing the distance between the entities 130 on the adjacent pins 120, thereby being beneficial to reducing the probability of short circuit of the entities 130 on the adjacent pins 120.

For example, after the lead frame structure 100 and the chip are encapsulated by the molding compound to form a package structure, the package structure needs to be soldered to the substrate through a solder wetting layer. Therefore, in the case that the bottom 135 of the entity 130 is exposed by the molding compound, the entity 130 on the adjacent pins 120 is staggered, which is beneficial to reducing the probability of short circuit of the entity 130 on the adjacent pins 120 due to the connection of the solder wetting layers.

As an example, as shown in fig. 5 (a), the number of the pins 120 is plural on either side of the connection bar 140, and the layout of the entities 130 on the plurality of pins 120 includes that the positions of the entities 130 on the different pins 120 are advanced toward the base island 110.

That is, on either side of the tie bar 140, the closer the tie bar 140 is to the land 110, the greater the distance from the entity 130 on the lead 120 to the land 110.

Since the length of the pins 120 adjacent to the ribs 140 is the largest, that is, the smaller the distance from the pins 120 to the ribs 140, the longer the length of the pins 120, and accordingly, the smaller the supporting force of the pins 120 with longer lengths to the end close to the base island 110, the layout of the entities 130 on the pins 120 is in progressive arrangement, that is, the entities 130 are closer to the base island 110 on the pins 120 with longer lengths, so that the entity 130 can play a role in supporting the pins 120 close to the end of the base island 110, which is beneficial to making the supporting effect of the entities 130 to the pins 120 better.

In other specific embodiments, as shown in fig. 5 (b) or fig. 5 (c), the layout of the entities 130 on the plurality of pins 120 may just as well be satisfied that the entities 130 on adjacent pins 120 are arranged in a staggered manner on either side of the connecting rib 140.

It should be noted that, at a plurality of top corner positions of the frame unit 101, the layout of the entities 130 may be the same or different, so long as it is satisfied that the undesired area in the leads 120 can be encapsulated.

For example, the layout of the entity 130 may include any one or more of fig. 5 (a) -5 (e).

It should be noted that the layout of the entities 130 on both sides of the same connecting rib 140 may be the same or different.

In this embodiment, the material of the entity 130 includes one or more of tungsten, aluminum, copper, titanium, silver, gold, platinum, nickel, iron, and alloys thereof. As an example, the material of the entity 130 is copper or iron-nickel alloy. The hardness of the metal or metal alloy material is relatively high, and thus can support the pins 120.

In other embodiments, the material of the entity may also be other suitable materials, for example, non-metals.

In this embodiment, the entity 130 and the pin 120 are integrally formed, and accordingly, the entity 130 and the pin 120 are made of the same material.

The entity 130 and the pin 120 are integrated, so that the bonding strength between the entity 130 and the pin 120 is improved. Moreover, the entity 130 and the leads 120 can be formed by the same process, reducing the complexity of preparing the leads 120 and the entity 130.

It should be noted that, in other embodiments, the entity and the pins may be in a non-integral structure, for example, the entity may be welded on the back of the pins or adhered on the back of the pins by an adhesive film.

In this embodiment, the bottom 126 of the outer leads 122 is flush with the bottom 135 of the body 130 on the side of the back 125 of the leads 120.

In one aspect, the bottom 126 of the outer lead 122 is flush with the bottom 135 of the body 130, which is advantageous for increasing the thickness of the body 130, thereby further enhancing the supporting effect of the body 130 on the lead 120, and correspondingly further enhancing the deformation resistance of the leadframe structure 100.

Moreover, the inner leads 121 are located in the half-etched region of the leads 120, that is, the step of the back surface 125 of the leads 120 can be formed by etching, so that when the body 130 is integrally formed with the leads 120, the bottom 126 of the outer leads 122 is flush with the bottom 135 of the body 130, thereby facilitating the simultaneous obtainment of the outer leads 122 and the body 130, and reducing the complexity of the process for forming the leads 120 and the body 130.

On the other hand, the bottom 126 of the outer lead 122 is flush with the bottom 135 of the entity 130, which is beneficial to improving the flatness of the bottom of the leadframe structure 100, so as to facilitate the subsequent plastic packaging process.

Because the bottom 126 of the outer lead 122 is flush with the bottom 135 of the body 130, the bottom 135 of the body 130 can be exposed while the bottom 126 of the outer lead 122 is exposed by the molding compound after the molding process, so that the body 130 is welded to the substrate when the outer lead 122 is welded to the substrate, thereby improving the bonding strength between the package structure and the substrate.

It should be noted that, in other embodiments, the bottom of the entity may be higher than the bottom of the outer leads, that is, the bottom of the entity is closer to the device carrying surface 115 of the base island 110.

It should be further noted that the width W1 of the entity 130 (as shown in fig. 5 (a)) is smaller than or equal to the width W2 of the inner lead 121 (as shown in fig. 5 (a)).

The width W1 of the entities 130 is smaller than or equal to the width W2 of the inner leads 121, so that the entities 130 located on the adjacent inner leads 121 have a space therebetween, thereby being beneficial to reducing the probability of occurrence of a short circuit problem between the entities 130 located on the adjacent inner leads 121.

As an example, the width W1 of the entity 130 is equal to the width W2 of the inner pin 121.

The width W1 of the entity 130 is equal to the width W2 of the inner lead 121, which is beneficial to further reducing the complexity of preparing the lead 120 and the entity 130.

As shown in fig. 5 (a), the ratio of the length L1 to the width W1 of the entity 130 is not necessarily too small. If the ratio of the length L1 to the width W1 of the entity 130 is too small, the length L1 of the entity 130 is too small under the condition that the width W1 of the entity 130 is constant, so that the surface area of the entity 130 is too small, the supporting effect of the entity 130 on the pin 120 is not good, and accordingly, the effect of improving the deformation resistance of the lead frame structure 100 is not ideal. In this embodiment, the ratio of the length L1 to the width W1 of the entity 130 is greater than or equal to 2.

The length L1 of the entity 130 is preferably not too large. If the length L1 of the entities 130 is too large, the risk of short-circuiting between entities 130 on adjacent pins 120 is easily increased when soldering the package structure including the leadframe structure 100 to a substrate. In this embodiment, the length L1 of the entity 130 is less than or equal to 1/2 of the length of the pin 120 where the entity 130 is located.

In this embodiment, the shortest distance between the adjacent entities 130 on different leads 120 is greater than or equal to 1.5 times the distance between the adjacent leads 120, and since the solder wetting layer is formed on the bottom 135 surface of the entity 130 later, the size of the solder wetting layer is greater than the size of the bottom 135 surface of the entity 130, by setting the shortest distance between the adjacent entities 130 on different leads 120 to be greater than or equal to 1.5 times the distance between the adjacent leads 120, the probability of short circuit between the adjacent entities 130 on different leads 120 is advantageously reduced.

Correspondingly, the invention further provides a packaging structure. Fig. 7 is a schematic cross-sectional view of an embodiment of the package structure of the present invention.

Referring to fig. 7 in combination with fig. 4 to 6, the package structure 200 includes the lead frame structure 100 according to any of the foregoing embodiments, a chip 210 disposed on the device carrying surface 115 of the base island 110 and electrically connected to the leads 120, and a molding compound 220 for molding the lead frame structure 100 and the chip 210.

The entity 130 can support the pins 120, so that the probability of deformation caused by insufficient supporting force of the pins 120 is reduced, and the deformation resistance of the lead frame structure 100 is correspondingly improved, thereby being beneficial to improving the covering capacity of the plastic package material 220 on the pins 120 in the plastic package process, reducing the probability of exposing the undesired exposed areas of the pins 120, and further improving the performance of the package structure 200.

In this embodiment, the package structure 200 is a quad flat no-lead (QFN) package structure. In other embodiments, the package structure may be other types of package structures, which are not illustrated herein.

For a detailed description of the leadframe structure 100, reference may be made to the content of the foregoing embodiments, and the details are not repeated here.

The chip 210 is disposed on the device carrying surface 115 of the base island 110, and the chip 210 is electrically connected with the pins 120, so as to obtain a packaging structure with a certain function, and achieve the functional requirement of the product.

In this embodiment, the package structure 200 further includes a lead 230 connecting the chip 210 and the leads 120. The leads 230 are used to make electrical connection between the chip 210 and the pins 120. Specifically, the material of the lead 230 is conductive metal.

The molding compound 220 is used for protecting the chip 210 from mechanical impact, abrasion and environmental factors (such as humidity change, etc.), and molding the chip 210 and the lead frame structure 100 into a whole to obtain a package structure.

Note that, the lead frame structure 100 in the package structure is a cut lead frame structure 100, and thus, as an example, the lead frame structure 100 in the package structure includes only one frame unit 101.

In this embodiment, the pins 120 include an inner pin 121 and an outer pin 122 connected to each other, and the outer pin 122 is located at an end of the inner pin 121 away from the base island 110.

The outer leads 122 serve as lead pads (pads) for electrical connection with external circuitry, and thus the molding compound 220 exposes the bottoms 126 of the outer leads 122 to electrically connect the leads 120 with external circuitry.

In this embodiment, the molding compound 220 includes an epoxy resin. The epoxy resin has the advantages of low shrinkage, good cohesiveness, good corrosion resistance, excellent electrical property, low cost and the like. In other embodiments, other suitable encapsulating materials may be used.

In this embodiment, the inner leads 121 are provided with the entities 130, so that the molding compound 220 also exposes the bottoms 135 of the entities 130.

The plastic molding compound 220 also exposes the bottom 135 of the entity 130, that is, the thickness H1 of the entity 130 is larger, which is beneficial to enhancing the supporting effect of the entity 130 on the inner pins 121, and correspondingly, is beneficial to further improving the deformation resistance of the lead frame structure 100.

In addition, the molding compound 220 also exposes the bottom 135 of the entity 130, so that when the backside 125 of the leads 120 exposed by the molding compound 220 is subsequently soldered to the substrate, the entity 130 is also soldered to the substrate, thereby improving the bonding strength between the package structure 200 and the substrate.

Specifically, the package structure 200 further includes a solder wetting layer 240 disposed on the bottom 126 of the outer leads 122 and the bottom 135 of the body 130 exposed to the molding compound 220.

The solder wetting layer 240 is disposed on the bottom 126 of the outer leads 122 and the bottom 135 of the body 130 exposed to the molding compound 220, so that the package structure 200 is soldered to the substrate through the solder wetting layer 240.

The thickness of the solder wetting layer 240 should not be too small or too large. If the thickness of the solder wetting layer 240 is too small, the bonding strength of the package structure 200 to the substrate is easily poor, and if the thickness of the solder wetting layer 240 is too large, the probability of shorting the entity 130 on the adjacent pin 120 is easily increased. Thus, as an example, the thickness of the solder wetting layer 240 ranges from 8 microns to 15 microns.

In this embodiment, the material of the solder wetting layer 240 may include an alloy of one or more of tin, nickel, palladium, and silver. As an example, the material of the solder wetting layer 240 is tin.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims (19)

1. A lead frame structure, comprising:

A base island;

The pins are arranged at intervals with the base islands, the back surfaces of the pins are provided with entities, the number of the entities on the same pin is one or more, and the back surfaces of the pins face away from the device bearing surfaces of the base islands.

2. The leadframe structure of claim 1, wherein the leadframe structure comprises a frame cell comprising the base island and a pin;

the frame unit also comprises connecting ribs, wherein the connecting ribs are connected with the base island and the top angle of the frame unit, and the connecting ribs are mutually spaced from the pins;

The entity is positioned on the pin close to the connecting rib.

3. The leadframe structure of claim 1, wherein the leadframe structure comprises a frame cell comprising the base island and a pin;

the frame unit also comprises connecting ribs, wherein the connecting ribs are connected with the base island and the top angle of the frame unit, and the connecting ribs are mutually spaced from the pins;

And on any side of the connecting rib, the entities on the adjacent pins are staggered.

4. The leadframe structure of claim 3, wherein the number of pins is plural on either side of the tie bar, and the placement of entities on the plurality of pins includes advancing the locations of entities on different ones of the pins toward the submount.

5. The leadframe structure of claim 1, wherein the entity is of unitary construction with the pins;

or the entity is welded on the back of the pin;

or the entity is stuck on the back of the pin.

6. The leadframe structure of any one of claims 1 to 5, wherein the leads comprise inner leads and outer leads connected to each other, the outer leads being located at an end of the inner leads remote from the submount, the inner leads being provided with the entity.

7. The leadframe structure of claim 6, wherein the backside of the leads have steps, the leads including inner leads at recessed locations of the steps, and outer leads connected to the inner leads.

8. The leadframe structure of claim 6, wherein the bottom of the outer leads are flush with the bottom of the solid body on the backside of the leads.

9. The leadframe structure of claim 6, wherein the physical width is less than or equal to the width of the inner leads.

10. The leadframe structure according to any one of claims 1 to 5, wherein the ratio of the length to the width of the body is greater than or equal to 2.

11. The leadframe structure according to any one of claims 1 to 5, wherein the length of the entity is less than or equal to 1/2 of the length of the pin in which the entity is located.

12. The leadframe structure according to any one of claims 1 to 5, wherein a shortest distance between adjacent ones of the entities located on different ones of the leads is greater than or equal to 1.5 times a pitch between adjacent ones of the leads.

13. The leadframe structure according to any one of claims 1 to 5, wherein when the number of entities on the same lead is plural, a distance between the entities on the same lead is greater than or equal to a width of the lead on which the entities are located.

14. The leadframe structure of any one of claims 1 to 5, wherein the solid material comprises one or more of tungsten, aluminum, copper, titanium, silver, gold, platinum, nickel, iron, and alloys thereof.

15. A package structure, comprising:

the leadframe structure according to any one of claims 1 to 14;

the chip is arranged on the device bearing surface of the base island and is electrically connected with the pins;

And plastic packaging the lead frame structure and the chip.

16. The package structure of claim 15, wherein the leads include inner and outer leads connected, and the outer leads are located at an end of the inner leads remote from the submount, the inner leads having the entity disposed thereon;

And the plastic packaging material exposes the bottoms of the outer pins.

17. The package structure of claim 16, wherein the molding compound exposes a bottom of the body.

18. The package structure of claim 17, further comprising a solder wetting layer at the bottom of the outer leads and at the bottom of the solid body exposed to the molding compound.

19. The package structure of claim 18, wherein the solder wetting layer has a thickness in the range of 8 microns to 15 microns.