Pin welding method for ceramic dual-in-line packaging

Abstract

The invention discloses a pin welding method for ceramic dual-in-line packaging, which is characterized in that two bottom supports are arranged on each of two side slitter edges of a prepared dual-in-line pin frame, the slitter edges of the pin frame are bent, and the relative positions of a ceramic base and pins are limited through the bottom supports at the two ends of the pins; and then assembling the solder strips, and then integrally entering a welding furnace for welding. According to the method, the problems of floating and deviation of the pins in the welding process of the ceramic shell are solved, and the alignment precision of welding is improved. And meanwhile, adhesion pollution of graphite ash can be avoided, and the electroplating yield is increased.

Description

Technical Field

[0001] The invention relates to a pin welding method of a chip packaging structure, in particular to a pin welding method of a ceramic dual in-line package. Background Art

[0002] Ceramic Dual In-line Package (CDIP) is a sealed package for integrated circuits. The corresponding integrated circuit has a rectangular shape and consists of a ceramic shell and a cover surrounding a dual in-line lead frame, that is, there are two rows of parallel metal pins on both sides of the rectangular integrated circuit. The components of the ceramic dual in-line package can be soldered in the through holes of the printed circuit board electroplating, or inserted into the DIP socket. Ceramic dual in-line package is widely used in the packaging of various integrated circuits, optocoupler devices, MEMS, etc. with a small number of pins and low assembly density requirements.

[0003] In conventional ceramic dual in-line packages, the pins are assembled with the ceramic shell through solder bars and then inserted into a graphite welding mold. Then, graphite pressing blocks are used to press both sides of the pins, and the whole is placed in a welding furnace for welding. When this welding process is used, graphite ash is likely to adhere to the lead frame during the welding process. During subsequent electroplating, the locations contaminated by graphite ash are not easy to be plated with gold, thus affecting the quality of electroplating. In addition, due to the large specific heat capacity of the graphite welding mold and the graphite pressing blocks that press the pins, the temperature of the graphite material drops relatively slowly after leaving the high temperature zone of the welding furnace, which slows down the cooling rate of the solder and makes it difficult to control the flow of the solder. This can easily cause the lead frame to float or tilt relative to the ceramic shell as a whole. Figure 1 and Figure 2 As shown, it affects the welding quality. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a pin welding method for a ceramic dual in-line package is proposed to solve the problem in the prior art that the lead frame floats or tilts relative to the ceramic shell as a whole, and the problem that graphite ash adheres to the lead frame during welding, thereby affecting the quality of subsequent electroplating.

[0005] Technical solution: A method for welding pins of a ceramic dual in-line package, comprising: Step 1: preparing a double-row lead frame, wherein a pair of sheet-like protrusions are respectively provided on the inner sides of the middle parts of the scrap edges on both sides of the double-row lead frame, and the pair of sheet-like protrusions are symmetrical about the vertical midline of the scrap edges; Step 2: Bending the waste edges on both sides of the double-row lead frame, so that the two sides of the double-row lead frame with pins are in an "eight"-shaped structure that is wide at the bottom and narrow at the top, and the distance between the tops of the opposite pins is less than the width of the ceramic base; after the bending process, the sheet-like protrusions on the horizontal parts of the waste edges on both sides form the bottom support of the ceramic base; Step 3: Using the elasticity of the “eight”-shaped structure to open the top of the structure outward, the ceramic base is placed between two opposite rows of pins, and the bottom of the ceramic base contacts the bottom brackets on both sides; Step 4: placing solder strips between the two sides of the ceramic base and the pins, and the solder strips are pressed against the sides of the ceramic base by the elastic force of the "eight"-shaped structure; Step 5: Place the assembled structure in a welding furnace for brazing so that each pin is connected to the pads on both sides of the ceramic base.

[0006] Furthermore, in the step 2, a trapezoidal bending die is used to bend the waste edges on both sides of the double-row lead frame.

[0007] Furthermore, the solder strip is a sheet of Ag72Cu28 solder.

[0008] Furthermore, the double-row lead frame is made of an iron-nickel constant expansion alloy with a grade of 4J42.

[0009] Beneficial effect: The pin welding method of the ceramic dual in-line package of the present invention has two bottom brackets on the waste edges of the prepared dual in-line pin frame on both sides, the waste edges of the pin frame are bent, and the relative positions of the ceramic base and the pins are limited by the bottom brackets at both ends of the pins, and then the solder strips are assembled and the whole is put into the welding furnace for welding. This method solves the problem of pin floating and deviation during the welding process of the ceramic shell, and improves the alignment accuracy of the welding. At the same time, this method can also avoid the adhesion and pollution of graphite ash and improve the electroplating yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the overall floating of the lead frame relative to the ceramic housing caused by the conventional welding process; Figure 2 A schematic diagram showing that the lead frame is tilted relative to the ceramic housing as a whole due to the conventional welding process; Figure 3 This is a schematic diagram of the double-row lead frame structure obtained in step 1; Figure 4 This is a schematic diagram of the double-row lead frame structure obtained in step 2; Figure 5 This is a schematic diagram of the figure eight structure of the double-row lead frame structure obtained in step 2; Figure 6 This is a schematic diagram of the structure obtained in step 4. DETAILED DESCRIPTION

[0011] The present invention will be further explained below in conjunction with the accompanying drawings.

[0012] A method for welding pins of a ceramic dual in-line package, comprising: Step 1: Prepare by etching Figure 3 The double-row lead frame 1-8 shown in the figure has a pair of sheet-like protrusions 1-2 respectively arranged on the inner sides of the middle of the waste edges 1-3 on both sides of the double-row lead frame 1-8, and the pair of sheet-like protrusions 1-2 are symmetrical about the vertical center line of the waste edges 1-3. The material of the double-row lead frame 1-8 is an iron-nickel fixed expansion alloy with a grade of 4J42.

[0013] Step 2: Use a trapezoidal bending die to bend the waste edges 1-3 on both sides of the double-row lead frame 1-8, so that the two sides of the double-row lead frame 1-8 with the pins 1-4 are in an "eight"-shaped structure with a wide bottom and a narrow top, such as Figure 4 , Figure 5 In the structure after bending, the distance between the tops of the opposite pins 1-4 is smaller than the width of the ceramic base 1-1, and the sheet-like protrusions 1-2 on the horizontal parts of the waste edges 1-3 on both sides form the bottom support of the ceramic base 1-1, and the material of the ceramic base 1-1 is alumina ceramic.

[0014] Step 3: Using the elasticity of the "eight"-shaped structure, the bottom of the "eight"-shaped structure is slightly retracted inward to open the top of the "eight"-shaped structure outward, and then the ceramic base 1-1 is placed between two opposite rows of pins 1-4. The bottom of the ceramic base 1-1 is in contact with the bottom support in the middle of both sides, that is, the bottom support formed by the protrusion 1-2 just supports the bottom surface of the ceramic base 1-1, which effectively limits the relative position of the ceramic base 1-1 and the pin 1-4, so that the large foot part at the top of the pin 1-4 will not exceed the pad 1-6 area on the side of the ceramic base 1-1, and no deviation will be found.

[0015] Step 4: Place solder strips 1-7 between the two sides of the ceramic base 1-1 and the pins 1-4. The solder strips 1-7 are Ag72Cu28 solder flakes. The solder strips 1-7 are pressed against the sides of the ceramic base 1-1 by the elastic force of the "eight"-shaped structure. Figure 6 shown.

[0016] Step 5: Place the assembled structure in a welding furnace for brazing, so that each pin 1-4 is connected to the pads 1-6 on both sides of the ceramic base 1-1. Since the entire welding process does not require the use of a graphite welding mold, graphite ash pollution is reduced, and the welding and electroplating yield rate is improved, thereby ensuring that the device avoids failure during mechanical testing and later use.

[0017] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for soldering pins of a ceramic dual in-line package, characterized in that: include: Step 1: preparing a double-row lead frame (1-8), wherein a pair of sheet-like protrusions (1-2) are respectively provided on the inner sides of the middle parts of the waste edges (1-3) on both sides of the double-row lead frame (1-8), and the pair of sheet-like protrusions (1-2) are symmetrical about the vertical midline of the waste edges (1-3); Step 2: bending the waste edges (1-3) on both sides of the double-row lead frame (1-8) so that the two sides of the double-row lead frame (1-8) with the pins (1-4) present an "eight"-shaped structure that is wider at the bottom and narrower at the top, and the distance between the tops of the opposite pins (1-4) is smaller than the width of the ceramic base (1-1); after the bending process, the sheet-like protrusions (1-2) on the horizontal parts of the waste edges (1-3) on both sides form the bottom support of the ceramic base (1-1); Step 3: using the elasticity of the "eight"-shaped structure to open the top of the structure outward, placing the ceramic base (1-1) between two opposite rows of pins (1-4), with the bottom of the ceramic base (1-1) in contact with the bottom brackets on both sides; Step 4: placing solder strips (1-7) between the two sides of the ceramic base (1-1) and the pins (1-4), the solder strips (1-7) being pressed against the side surfaces of the ceramic base (1-1) by the elastic force of the "eight"-shaped structure; Step 5: Place the assembled structure in a soldering furnace for brazing, so that each pin (1-4) is connected to the soldering pads (1-6) on both sides of the ceramic base (1-1).

2. The method for soldering the pins of a ceramic dual in-line package according to claim 1, characterized in that: In the step 2, a trapezoidal bending die is used to perform bending processing on the waste edges (1-3) on both sides of the double-row lead frame (1-8).

3. The method for soldering the pins of a ceramic dual in-line package according to claim 1, characterized in that: The solder strip (1-7) is a sheet of Ag72Cu28 solder.

4. The method for soldering the pins of a ceramic dual in-line package according to any one of claims 1 to 3, characterized in that: The material of the double-row lead frame (1-8) is an iron-nickel constant expansion alloy with a grade of 4J42.

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