A dual-in-line ceramic package structure

Abstract

The utility model discloses a double row straight insertion type ceramic packaging structure, through being equipped with the chamfer on the bottom edge of two outer sides of the lead bonding pad of ceramic base, respectively facing the area of each lead bonding pad, when sending into brazing furnace and carrying out lead welding, part of solder flows and cools and is accumulated in the V-shaped included angle between the chamfer and lead, effectively prevents the situation that solder of prior art flows to the surface of lead frame in a large range because of "creeping tin", solves the rigidity of lead affected because of "creeping tin" in prior art, and the appearance qualified rate of product after electroplating in later period is improved.

Description

Technical Field

[0001] This utility model relates to a ceramic packaging structure, and more particularly to a dual in-line ceramic packaging structure. Background Technology

[0002] Dual in-line package (DIP) is a type of integrated circuit packaging. The integrated circuit is rectangular in shape, with two rows of parallel metal leads on both sides, called pin headers. DIP-packaged components can be soldered into plated through holes on a printed circuit board or inserted into a DIP socket.

[0003] The main body of a dual in-line package (DIP) is typically made of plastic or ceramic. Ceramic packages offer excellent hermeticity and are commonly used in devices requiring high reliability.

[0004] In the lead soldering process of a dual in-line package (DIP) ceramic package, the leads on the leadframe are first bent and adjusted to a vertical direction, ensuring they are parallel to the sides of the ceramic substrate. The ceramic substrate is then assembled with the leadframe, with each lead end corresponding to a pad on either side of the ceramic substrate. A flat solder pad is placed between each pad and lead. The assembly structure is stabilized by the clamping force of the two relatively parallel rows of leads on the leadframe against the solder pad and ceramic substrate. The assembly is then placed in a brazing furnace for soldering. The solder melts into a liquid upon heating, and as it wets the leads, "solder creep" occurs. Under the influence of gravity, the solder easily flows down the vertical leads to the surface of the leadframe.

[0005] Leads are typically made of copper alloys and may have tin or nickel plating on the surface. After the solder solidifies, it is in a metallic state, and its hardness differs from that of the lead material. When the solder covers the surface of the lead, it is equivalent to forming a composite structure on the outside of the lead. If the solder run-up is high, such as exceeding 1 / 2 of the lead diameter, the effective cross-sectional area of ​​the lead increases, and the overall rigidity will increase significantly, especially the bending stiffness and resistance to deformation.

[0006] In dynamic environments (such as vibration, temperature cycling, and mechanical shock), increased lead rigidity can become a disadvantage. For example, highly rigid leads struggle to buffer external forces or thermal stress through their own deformation. When temperatures change, the difference in thermal expansion coefficients between the leads and the solder generates stress, causing stress concentration at the solder joint root. Over time, this can lead to solder joint cracking. Furthermore, lead flexibility is crucial for absorbing dynamic stress. In automotive electronics and aerospace equipment, leads need to compensate for vibration through minute deformations. Excessive rigidity can cause leads to a loss of buffering capacity, making the solder joint a weak point for stress release and shortening fatigue life. Moreover, the aforementioned "tin creep" can also cause aesthetic defects in the finished product after electroplating. Summary of the Invention

[0007] Purpose of the invention: To address the aforementioned existing technology, a dual in-line ceramic package structure is proposed to solve the problem of "solder creep" that easily occurs during lead soldering.

[0008] Technical solution: A dual in-line ceramic package structure, including a ceramic substrate and a lead frame; the ceramic substrate has a top-opening structure with a cavity, and two rows of lead pads are arranged on a set of opposite outer sides of the ceramic substrate; the cavity of the ceramic substrate is used to mount the chip; the bottom edges of the two outer sides of the ceramic substrate with lead pads are chamfered, respectively, in the area facing each lead pad; the ends of the vertically arranged leads on the lead frame are respectively facing each lead pad; the V-shaped angle formed between the chamfer and the lead is used for lead soldering, during which some solder flows and cools and accumulates in the V-shaped angle at the bottom of the corresponding lead pad.

[0009] Furthermore, the included angle of the V-shape is 30°~60°.

[0010] Furthermore, the chamfer is a C-shaped chamfer.

[0011] Furthermore, the ceramic base is made of alumina ceramic, and the lead wire is made of iron-nickel constant expansion alloy.

[0012] Furthermore, a sealing ring for connecting the top cover plate is welded to the top of the ceramic base.

[0013] Furthermore, the surface of the ceramic packaging structure is also electroplated with a nickel-gold layer.

[0014] Beneficial Effects: This utility model discloses a dual-in-line ceramic package structure. By creating chamfers on the bottom edges of the two outer sides of the ceramic base where the lead pads are located, respectively, the area facing each lead pad is chamfered. During lead soldering in the brazing furnace, some solder flows, cools, and accumulates at the bottom of the corresponding lead pad, within the V-shaped angle formed by the chamfer and the lead. This effectively prevents the solder from flowing extensively onto the surface of the lead frame due to "tin creep," which is a problem in existing technologies. It also solves the problem of "tin creep" affecting the rigidity of the leads and improves the appearance qualification rate of the product after electroplating. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the transverse half-section structure of the ceramic base of this utility model; Figure 2 This is a longitudinal cross-sectional schematic diagram of the ceramic base of this utility model; Figure 3 This is a top view of the ceramic packaging structure of this utility model after lead wire welding and assembly; Figure 4 This is a longitudinal cross-sectional view of the ceramic packaging structure of this utility model after lead wire welding and assembly; Figure 5 yes Figure 4 Enlarged structural diagram at point E; Figure 6 This is a longitudinal cross-sectional view of an existing ceramic packaging structure after lead wire welding assembly. Figure 7 This is a schematic diagram of the transverse half-section structure of the ceramic packaging structure of this utility model after lead wire welding; Figure 8 This utility model relates to a ceramic packaging structure after lead wire soldering. Figure 5 The corresponding structural diagram. Detailed Implementation

[0016] The present invention will be further explained below with reference to the accompanying drawings.

[0017] A dual in-line ceramic package structure includes a ceramic base and a lead frame.

[0018] like Figure 1 , Figure 2 As shown, the ceramic substrate 1 has a top-opening structure with a cavity, and two rows of lead pads 1-3 are disposed on a set of opposite outer surfaces of the ceramic substrate 1. The cavity of the ceramic substrate 1 is used to mount the chip, and the pads inside the cavity for connecting to the chip are electrically connected to the lead pads 1-3 on the outer surface of the ceramic substrate 1 through structures such as metallized through holes inside the ceramic substrate 1.

[0019] In this embodiment, the ceramic base 1 has chamfers 1-2 on the bottom edges of the two outer sides of the lead pads 1-3, respectively, facing the area of ​​each lead pad 1-3.

[0020] like Figures 3 to 5 As shown, before wire bonding, each lead 2-1 on the lead frame 2 is first bent and adjusted to a vertical direction, so that each lead 2-1 is parallel to the side of the ceramic base 1. The ceramic base 1 and lead frame 2 are then assembled, with the end of each lead 2-1 aligned with the lead pads 1-3 on both sides of the ceramic base 1. A flat solder pad is placed between each lead pad 1-3 and 2-1. Because the solder pad is relatively thin, [the diagram continues]. Figure 5 (Not shown in the diagram). The stability of the assembly structure is maintained by the clamping force of the two relatively parallel rows of leads 2-1 on the lead frame 2 in the assembly structure on the solder sheet and the ceramic base 2.

[0021] In the assembly structure, each vertical lead wire 2-1 forms a V-shaped angle with the chamfer 1-2 of the bottom edge. The design range of this angle is 30° to 60°.

[0022] Figure 6This is a longitudinal cross-sectional view of the existing ceramic packaging structure after lead wire welding assembly. In the prior art, the ceramic base 1 has two outer sides with unprocessed chamfered bottom edges of the lead wire pads 1-3.

[0023] In this embodiment, the assembled structure is sent into a brazing furnace for welding. During the welding process, the solder is heated and becomes liquid. Some of the solder 3 flows into the V-shaped angle at the bottom of the lead pads 1-3 where it is located. After cooling, it accumulates in this angle. Figure 7 , Figure 8 As shown, this effectively prevents solder from flowing extensively onto the surface of the lead frame 2 due to "solder creep". By setting this chamfer 1-2 structure, the rigidity of the lead wires affected by "solder creep" in the prior art is solved, and the appearance qualification rate of the product after subsequent electroplating is improved.

[0024] In this embodiment, during the green ceramic forming process of the ceramic base 1, the bottom edges of the lead pads 1-3 directly below the ceramic base 1 are chamfered, and then the ceramic base 1 for assembly is formed after high-temperature sintering.

[0025] In the above structure, the ceramic base 1 is made of alumina ceramic; a sealing ring 4 for connecting the top cover plate is also welded to the top of the ceramic base 1; the lead wire 2-1 and the sealing ring 4 can be made of iron-nickel constant expansion alloy 4J42 alloy; the solder bar 3 can be made of silver-copper alloy solder Ag. 72 Cu 28 .

[0026] After welding, the above structure requires nickel-gold plating and inspection. During nickel-gold plating, the sealing ring 4 is typically connected to the metal portion of the ceramic base 1 via a metallization structure, facilitating effective plating of the overall structure. After plating, the crossbeam at one end of the lead frame 2 is cut off, making it easier to remove the metal connection between the sealing ring 4 and the ceramic base 1 by grinding.

[0027] In this embodiment, the ceramic base 1 has external dimensions of 17.78mm × 7.87mm, and the width of the end of the lead wire 2-1 is 1.20mm, which is obtained through ANSYS simulation. A C0.15mm chamfer is adopted, that is, a bevel with a horizontal and vertical distance of 0.15mm is machined from the edge at a 45° angle.

[0028] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A dual in-line ceramic package structure, characterized in that, The system includes a ceramic base (1) and a lead frame (2). The ceramic base (1) has a top-opening structure with a cavity, and two rows of lead pads (1-3) are arranged on a set of opposite outer sides of the ceramic base (1). The cavity of the ceramic base (1) is used to install chips. On the bottom edges of the two outer sides of the ceramic base (1) where the lead pads (1-3) are located, chamfers (1-2) are respectively opened in the area facing each lead pad (1-3). The ends of each vertically arranged lead (2-1) on the lead frame (2) are respectively facing each lead pad (1-3). The V-shaped angle formed between the chamfer (1-2) and the lead (2-1) is used for lead brazing, so that some solder (3) flows and cools and accumulates in the V-shaped angle at the bottom of the corresponding lead pad (1-3).

2. The dual in-line ceramic package structure according to claim 1, characterized in that, The angle of the V-shape is 30°~60°.

3. The dual in-line ceramic package structure according to claim 2, characterized in that, The chamfer (1-2) is a C-type chamfer.

4. The dual in-line ceramic package structure according to any one of claims 1-3, characterized in that, The ceramic base (1) is made of alumina ceramic, and the lead wire (2-1) is made of iron-nickel constant expansion alloy.

5. The dual in-line ceramic package structure according to any one of claims 1-3, characterized in that, The top of the ceramic base (1) is also welded with a sealing ring (4) for connecting the top cover plate.

6. The dual in-line ceramic package structure according to any one of claims 1-3, characterized in that, The surface of the ceramic packaging structure is also electroplated with a nickel-gold layer.

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