Lead frame

Abstract

A lead frame relates to the technical field of chip packaging and comprises a wafer base, a frame, a fixed column and pins, the pins are arranged on the side of the wafer base, all the pins are connected with the fixed column and fixed with the frame through the fixed column, and all the pins are separated from the frame. In the process of packaging a chip and separating to form a single chip after injection molding by adopting the lead frame, as the pins are separated from the frame, and the pins do not need to be cut, the pins have no cut surfaces, and each surface of the pins is electroplated to form an electroplated layer in the electroplating process, that is, the electroplated layer covers the pins, so that the production efficiency of the lead frame is improved. Therefore, during SMT, the pins are easy to have a stable tin climbing characteristic, and the reliability of tin soldering is higher.

Description

Technical Field

[0001] The utility model relates to the technical field of chip packaging, in particular to a lead frame. Background Art

[0002] Lead frame is an important component in the chip packaging process. At present, traditional packaging types such as QFP, TSOP, SOT, SOP are widely used in chip packaging in the fields of consumer electronics and automotive electronics. These packaging types with long pins use lead frames such as Figure 1 As shown, after injection molding and electroplating, the seagull-shaped pins are formed by cutting (cutting off the fixed column 3), separation (cutting and separating to form a single chip, this process will cut off the end of the pin 4 to separate the pin 4 from the frame 2), and molding (bending the pin to form a seagull-shaped pin). However, after molding, cutting and separation, the cut surface of the pin is the copper surface, which will oxidize. During SMT, the cut surface of the pin is less likely to have stable tin creep characteristics, and the soldering reliability is low. Utility Model Content

[0003] In view of this, the utility model provides a lead frame, which is more likely to have a stable solder creeping feature during SMT and has higher soldering reliability.

[0004] In order to achieve the above-mentioned purpose, the utility model provides the following technical solutions.

[0005] The lead frame includes a wafer base, a frame, fixed columns and pins. The pins are arranged on the side of the wafer base. Each pin is connected to the fixed column and fixed to the frame through the fixed column. Each pin is separated from the frame.

[0006] When the chip is packaged using the lead frame and separated into individual chips after injection molding, the pins do not need to be cut because the pins are separated from the frame, so the pins have no cut surfaces. The pins are electroplated on all sides to form an electroplating layer during the electroplating process, that is, the electroplating layer covers the pins, so that the pins are prone to stable tin creeping characteristics during SMT, and the reliability of soldering is higher.

[0007] Furthermore, it also includes auxiliary positioning posts, each pin is connected to the auxiliary positioning posts, and the auxiliary positioning posts are arranged side by side with the fixed posts and connected to the frame. The pins are separated from the frame, and since the pins have only one connection point with the positioning posts, the pins are prone to warping and deformation during the transportation process after the lead frame is manufactured. Adding auxiliary positioning posts arranged side by side with the positioning posts adds a connection point to the pins, making it difficult for the pins to warp and deform. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the structure of an existing lead frame.

[0009] Figure 2It is a schematic structural diagram of the lead frame of the utility model.

[0010] Figure 3 It is a schematic diagram of the seagull-shaped pins formed after the chip is packaged using the lead frame of the utility model.

[0011] Reference numerals include:

[0012] Wafer base 1, frame 2, fixed column 3, pin 4, auxiliary positioning column 5, plastic package 6. DETAILED DESCRIPTION

[0013] The present invention is described in detail below in conjunction with specific embodiments.

[0014] like Figure 2 As shown, the lead frame of this embodiment includes a wafer base 1, a frame 2, fixed columns 3 and pins 4. The pins 4 are arranged on both sides of the wafer base 1. There are 4 fixed columns 3. One fixed column 3 connects the pins 4 on one side of the wafer base 1 and the frame 2 to fix the pins 4. One fixed column 3 connects the pins 4 on the other side of the wafer base 1 and the frame 2 to fix the pins 4. Two fixed columns 3 are respectively arranged on the two outer sides of the wafer base 1 to connect the wafer base 1 and the frame 2 to fix the wafer base 1. The length of the pins 4 is designed so that each pin 4 is separated from the frame 2 and is not connected to the frame 2. In this way, when the lead frame of this embodiment is used to package the chip, in the process of separating the chip into a single chip after injection molding, since the pins 4 are separated from the frame 2, Figure 2 When cutting at the middle dotted line b, pin 4 does not need to be cut, so pin 4 has no cut surface. Pin 4 is electroplated on all sides to form a plating layer during the electroplating process, that is, the plating layer covers pin 4. In this way, pin 4 is prone to stable tin creeping characteristics during SMT, and the reliability of soldering is higher.

[0015] See also Figure 3 The length of the pin 4 is designed so that it is just the right length after being bent into a seagull-shaped pin 4 during the molding process after the plastic package 6 is formed by injection molding.

[0016] like Figure 2As shown, the lead frame of this embodiment is also provided with auxiliary positioning posts 5. There are two auxiliary positioning posts 5, which are respectively arranged on both sides of the wafer base 1. Each auxiliary positioning post 5 connects each pin 4 and the frame 2 on that side of the wafer base 1, and is arranged side by side with the fixed posts 3 connecting these pins 4. The design of separating the pin 4 from the frame 2 results in one less connection point for the pin 4, which may be unstable. During transportation, the pin 4 is prone to warping and deformation. The purpose of adding the auxiliary positioning post 5 is to add a connection point to the pin 4, which is arranged side by side with the fixed post 3. In this way, the pin 4 has two connection points and is more firmly fixed, so it is not easy to warp and deform during transportation. During the chip packaging process, the auxiliary positioning post 5 is cut off together with the fixed post 3 in the rib cutting process to electrically separate the pins 4. In the subsequent molding process, the pin is bent to form a seagull-shaped pin, such as Figure 3 As shown, the pin is bent to form three sections d, e, and f. The auxiliary positioning column 5 is located at section e, and the incision produced by its cutting during the rib cutting process is also on the side of section e. This allows the side of section f to remain flat, without incisions and without exposed copper, thereby maintaining the tin plated during the electroplating process and maintaining wettability.

[0017] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model creation, rather than to limit the protection scope of the utility model creation. Although the utility model creation has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model creation can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the utility model creation.

Claims

1. A lead frame, comprising a wafer base, a frame, a fixed column and pins, wherein the pins are arranged on the side of the wafer base, each pin is connected to the fixed column and fixed to the frame through the fixed column, wherein the lead frame is characterized in that: The individual pins are separated from the frame.

2. The lead frame according to claim 1, wherein: It also includes auxiliary positioning posts, each pin is connected to the auxiliary positioning posts, the auxiliary positioning posts are arranged side by side with the fixed posts and are connected to the frame.

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