Lead frame and method for manufacturing the same

Abstract

A lead frame and a manufacturing method thereof, the lead frame comprising a pin group, a first surface and a second surface spaced apart from each other, and a through surface. The through surface extends downward from the first surface to the second surface. A plurality of first arc portions and a plurality of first protrusions interlaced with the first arc portions and protruding upward are formed at the connection between the through surface and the first surface. A plurality of second arc portions and a plurality of second protrusions interlaced with the second arc portions and protruding downward are formed at the connection between the through surface and the second surface. The manufacturing method mainly involves stamping a substrate twice, and the two stampings are performed from different surfaces of the substrate, thereby forming the lead frame. The present invention allows the stress on the lead frame to be evenly distributed on the first surface and the second surface, thereby avoiding the phenomenon of deformation of the lead frame due to stress accumulation.

Description

Technical Field

[0001] The present invention relates to a lead frame and a manufacturing method thereof, and in particular to a lead frame used for IC packaging, LED, passive components, etc. and a manufacturing method thereof. Background Art

[0002] See also Figure 1 A lead frame 8 used in IC packaging is known, comprising a flat metal pad (not shown), a plurality of pins 83 disposed around the pad, a first surface 81 formed at the top of the pins 83, a second surface 82 formed at the bottom of the pins 83, and a hollow space 84 formed between the pins 83 and extending from the first surface 81 to the second surface 82. The metal pad is used to fix a prefabricated chip thereon, and the pins 83 can be electrically connected to the chip by wire bonding technology using gold wires.

[0003] See also Figure 1 , 2 When the lead frame 8 is manufactured, a punching machine 9 is used to punch a substrate 80. The punching machine 9 includes a lower die 91 formed with a die cavity 911, and a punch 92 located above the lower die 91. The first surface 81 of the substrate 80 faces the punch 92, and the second surface 82 faces downward. During punching, the punch 92 punches downward toward the first surface 81 of the substrate 80 and penetrates the second surface 82, thereby removing a partial material 801 of the substrate 80 and forming the hollow space 84, and the pin 83 is formed around the hollow space 84. Due to the characteristics of the punching process, the first surface 81 faces the punch 92, and after punching, a smooth side is formed, and a plurality of arc surfaces 811 are located next to the pin 83. The second surface 82 becomes a burr side, and a plurality of burrs 821 are located next to the pin 83 and protrude downward.

[0004] Since the substrate 80 is stamped from the first surface 81 to the second surface 82 in the above-mentioned manufacturing method, the stress direction of the lead frame 8 is the same as that of the lead frame 8, and the lead frame 8 is easily deformed due to stress accumulation. Figure 3 The phenomenon of bending deformation is shown, and this problem needs to be improved. Summary of the invention

[0005] The object of the present invention is to provide a lead frame and a manufacturing method thereof which can overcome the disadvantages of the background technology.

[0006] The lead frame of the present invention comprises a pin group, a first surface and a second surface which are spaced apart from each other and defined by the pin group, and a through surface which extends downward from the first surface to the second surface and defines a hollow space located next to the pin group. A plurality of first arc portions in an arc shape are formed at the connection between the through surface and the first surface, and a plurality of first protrusion portions which are arranged staggered with the first arc portions and protrude upwards; a plurality of second arc portions in an arc shape are formed at the connection between the through surface and the second surface, and a plurality of second protrusion portions which are arranged staggered with the second arc portions and protrude downwards; the position of the second arc portion corresponds to the first protrusion in the upper and lower parts, and the position of the second protrusion corresponds to the first arc portion in the upper and lower parts.

[0007] The lead frame described in the present invention comprises a plurality of inner pins, each inner pin having a first side and a second side opposite to each other, one of the first arc portions being formed above the first side, one of the second protrusions being formed below the first side, one of the first protrusions being formed above the second side, and one of the second arc portions being formed below the second side.

[0008] The lead frame described in the present invention comprises a plurality of outer pins respectively corresponding to the inner pins in inner and outer directions, each outer pin having a third side and a fourth side opposite to each other, one of the first arc portions being formed above the third side, one of the second protrusions being formed below the third side, one of the first protrusions being formed above the fourth side, and one of the second arc portions being formed below the fourth side.

[0009] The manufacturing method of the lead frame of the present invention is used to manufacture the lead frame, and comprises step A: providing a substrate for making the lead frame, the substrate having a first surface and a second surface spaced apart. Step B: punching from the first surface of the substrate toward the second surface to form a part of the pin group. Step C: punching from the second surface of the substrate toward the first surface to form the rest of the pin group.

[0010] The manufacturing method of the lead frame described in the present invention is suitable for being carried out in conjunction with a first punching machine and a second punching machine, wherein the first punching machine has a first punch and the second punching machine has a second punch. In step B, the substrate is passed through the first punching machine, the first surface of the substrate faces upward and toward the first punch, and the first punch punches from the first surface to the second surface. The substrate is then turned over and transported to the second punching machine. In step C, the second surface of the substrate faces upward and toward the second punch, and the second punch punches from the second surface to the first surface.

[0011] In the manufacturing method of the lead frame of the present invention, the punching process in step B, turning over the substrate, and the punching process in step C are continuous and uninterrupted processes.

[0012] The manufacturing method of the lead frame described in the present invention is suitable for being carried out in conjunction with a first punching machine and a second punching machine, wherein the first punching machine has a first punch and the second punching machine has a second punch. In step B, the substrate is passed through the first punching machine, the first surface of the substrate faces upward and toward the first punch, and the first punch punches from the first surface to the second surface. The substrate is then rolled up and transported to the second punching machine. In step C, the substrate is rolled up, the second surface of the substrate faces upward and toward the second punch, and the second punch punches from the second surface to the first surface.

[0013] In the method for manufacturing the lead frame of the present invention, the positions of stamping on the substrate in step B and step C are arranged alternately.

[0014] The manufacturing method of the lead frame of the present invention comprises a plurality of inner pins and a plurality of outer pins corresponding to the inner and outer positions of the inner pins. Step B is stamping to form a part of the inner pins and the outer pins, and step C is stamping to form the rest of the inner pins and the outer pins.

[0015] The beneficial effect of the present invention is that the lead frame structure is innovatively manufactured by performing two stamping processes on different surfaces of the substrate, so that the stress can be evenly distributed on the first surface and the second surface of the lead frame, thereby achieving the effect of stress balance and avoiding the phenomenon of deformation of the lead frame due to stress accumulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which:

[0017] Figure 1 is a side cross-sectional schematic diagram illustrating a partial structure of a known lead frame;

[0018] Figure 2 is a flow chart illustrating a stamping process for manufacturing the known lead frame;

[0019] Figure 3 is a three-dimensional schematic diagram illustrating the bending deformation of the known lead frame;

[0020] Figure 4 is a top view schematically illustrating an embodiment of a lead frame of the present invention;

[0021] Figure 5 It is taken from Figure 4 A partial enlarged view of

[0022] Figure 6 is along Figure 5 A schematic cross-sectional view along line AA in FIG. 1 illustrates several inner legs of the embodiment;

[0023] Figure 7 is along Figure 5 A schematic cross-sectional view along line BB in FIG. 1 illustrates several outer legs of the embodiment;

[0024] Figure 8 is a step flow chart illustrating the process of a first embodiment and a second embodiment of a method for manufacturing a lead frame of the present invention;

[0025] Fig. 9 is a schematic diagram of an apparatus flow chart, illustrating the process of the first embodiment of the manufacturing method;

[0026] Fig.10 is a similar Figure 5 A top view schematic diagram of the present invention, in which the parts drawn with thin lines are stamped from a first surface of the lead frame toward a second surface during stamping, and the parts drawn with thick lines are stamped from the second surface toward the first surface during stamping;

[0027] Fig.11 is a similar Fig.10 A top view of the stamping process is shown in Figure 1. In the figure, thick and thin lines are used to distinguish the two stamping locations in different directions. Fig.11 The two punching positions of the present invention are compared with Fig.10 There can be other kinds of variations;

[0028] Fig.12 is a schematic diagram of an apparatus flow chart, illustrating the second embodiment of the method for manufacturing a lead frame of the present invention. DETAILED DESCRIPTION

[0029] Before the present invention is described in detail, it should be noted that similar elements are denoted by the same reference numerals in the following description.

[0030] See also Figures 4 to 6 An embodiment of the lead frame of the present invention is suitable for use in IC packaging. The lead frame is made of metal and is in a sheet shape, and includes a plurality of pad units 10 connected together. Each pad unit 10 includes a pad 1, a pin group 2, a first surface 3 and a second surface 4 spaced apart from each other, and a through surface 5.

[0031] The pad 1 is in the form of a flat plate, and a prefabricated chip (not shown) is fixed thereon during IC packaging.

[0032] The pin set 2 is arranged around the pad 1 and includes a plurality of inner pins 21 extending toward the pad 1 and a plurality of outer pins 22 extending away from the pad 1. The size of one end of each inner pin 21 adjacent to the pad 1 is larger than that of other parts. The positions of the outer pins 22 correspond to the inner and outer sides of the inner pins 21. The pin set 2 can be electrically connected to the chip by wire bonding technology during IC packaging.

[0033] The first surface 3 faces upward and is formed by the top surface of the solder pad 1 and the pin group 2. The second surface 4 faces downward and is formed by the bottom surface of the solder pad 1 and the pin group 2. It should be noted that the solder pad 1 is not necessary for the present invention. For example, the LOC (Lead On Chip) wire frame does not need to be provided with the solder pad 1. At this time, the first surface 3 and the second surface 4 are defined by the pin group 2.

[0034] The through-surface 5 extends downward from the first surface 3 to the second surface 4, and defines a hollow space 50 located beside the pad 1 and the pin group 2 and having a plurality of space portions 501. A plurality of arc-shaped first arc portions 51 and a plurality of first protrusions 52 that are staggered with the first arc portions 51 and protrude upward are formed at the connection between the through-surface 5 and the first surface 3. A plurality of arc-shaped second arc portions 53 and a plurality of second protrusions 54 that are staggered with the second arc portions 53 and protrude downward are formed at the connection between the through-surface 5 and the second surface 4. The position of the second arc portion 53 corresponds to the first protrusion 52 in the upper and lower directions, and the position of the second protrusion 54 corresponds to the first arc portion 51 in the upper and lower directions.

[0035] See also Figures 5 to 7 In this embodiment, the positions of the first arc portion 51, the first protrusion 52, the second arc portion 53, and the second protrusion 54 can be formed on the sides of the inner leg 21 and the outer leg 22 of the pin set 2. The specific description is as follows. In this embodiment, each inner leg 21 has a first side 211 and a second side 212 that are opposite to each other and extend from the first surface 3 to the second surface 4. One of the first arc portions 51 is formed above the first side 211, and one of the second protrusions 54 is formed below the first side 211. One of the first protrusions 52 is formed above the second side 212, and one of the second arc portions 53 is formed below the second side 212. Each outer leg 22 has a third side 221 and a fourth side 222 that are opposite to each other and extend from the first surface 3 to the second surface 4. One of the first arc portions 51 is formed above the third side 221, one of the second protrusions 54 is formed below the third side 221, one of the first protrusions 52 is formed above the fourth side 222, and one of the second arc portions 53 is formed below the fourth side 222.

[0036] The positions of the first arc portion 51, the first protrusion 52, the second arc portion 53, and the second protrusion 54 are related to the stamping direction during the manufacturing process of the lead frame, as described below. Figure 8 , 9 A first embodiment of the method for manufacturing a lead frame of the present invention is used to manufacture Figure 4 The lead frame is suitable for being used in conjunction with a first punch 61 and a second punch 62. The first punch 61 has a first upper die 613, a first punch 611 coupled to the bottom of the first upper die 613 and can be driven by the first upper die 613 to move downward, two first guide pillars 614, a first stripper plate 615, and a first lower die 612. The second punch 62 is located downstream of the first punch 61, and has a second upper die 623, a second punch 621 coupled to the bottom of the second upper die 623 and can be driven by the second upper die 623 to move downward, two second guide pillars 624, a second stripper plate 625, and a second lower die 622. Since the structures of the first punch 61 and the second punch 62 are not the focus of improvement of the present invention, they are no longer described and are only schematically shown in the figure. The manufacturing method of this first embodiment includes the following steps.

[0037] Step 71: Provide a substrate 20 for making the lead frame. The substrate 20 is a metal plate and has a first surface 3 and a second surface 4 spaced apart from each other.

[0038] Step 72: See Figures 6 to 9 , punching is performed from the first surface 3 of the substrate 20 toward the second surface 4 to form a part of the pin set 2. Specifically, in this step, the substrate 20 passes through the first punch 61, with the first surface 3 of the substrate 20 facing upward and toward the first punch 611, and the first punch 611 punches from top to bottom, thereby punching from the first surface 3 toward the second surface 4 to form a part of the inner leg 21 and the outer leg 22, and further forming the first arc portion 51 and the second protrusion 54. Then, the substrate 20 is turned over by a turning mechanism (not shown), at which time the second surface 4 of the substrate 20 faces upward, and the substrate 20 is then transported to the second punch 62.

[0039] Step 73: Punch from the second surface 4 of the substrate 20 toward the first surface 3 to form the remaining portion of the pin set 2. Specifically, since the substrate 20 is turned over previously, the second surface 4 of the substrate 20 faces upward and toward the second punch 621. Then, the second punch 621 is punched from top to bottom, thereby punching from the second surface 4 toward the first surface 3 to form the remaining portion of the inner leg 21 and the outer leg 2, and further forming the second arc portion 53 and the first protrusion 52. After the above process, the pad 1 ( Figure 5) are also formed.

[0040] It is worth mentioning that the first punching machine 61 and the second punching machine 62 can be continuously arranged machines, and the punching process of step 72, turning over the substrate 20, and the punching process of step 73 can be continuous and uninterrupted processes, so that the manufacturing process of the lead frame can be carried out continuously.

[0041] See also Fig.10 , the position of the first punching in step 72 corresponds to Fig.10 In the pattern shown, the thinner lines are located at the position of the second punch in step 73, corresponding to Fig.10 The pattern shown has thicker lines. Fig.10 In the lead frame shown, the thin line is the position where the first arc portion 51 is formed, and the thick line is the position where the first protrusion 52 is formed. The overall structure of the lead frame is completed by two stampings, and the two stampings are performed on different surfaces to evenly disperse the stamping stress. Furthermore, the positions of the two stampings are staggered, which has a better effect of evenly dispersing the stress.

[0042] See also Figure 5 , 6 9. In summary, since the present invention performs two stamping processes on different surfaces of the substrate 20, the structure of the lead frame produced is innovative. The first surface 3 and the second surface 4 of the lead frame are both formed with arcs and protrusions. The stress can be evenly distributed on the first surface 3 and the second surface 4, thereby achieving the effect of stress balance, and avoiding the phenomenon of deformation of the lead frame due to stress accumulation. Among them, the part of the first surface 3 formed with the first arc 51 and the part of the second surface 4 formed with the second arc 53 are smooth sides, and the part of the first surface 3 formed with the first protrusion 52 and the part of the second surface 4 formed with the second protrusion 54 are burr sides. The first protrusion 52 and the second protrusion 54 are burrs formed by the stamping process. In other words, the first surface 3 and the second surface 4 of the lead frame of the present invention both have smooth surfaces and burr surfaces, which is completely different from the structure of the known lead frame in which the smooth surfaces are all concentrated on one side and the burr surfaces are all concentrated on the other side.

[0043] From the above description, it can be seen that the spirit of the present invention is that two stamping processes can form different parts of the pin set 2, and the parts formed by the two stamping processes are arranged in a staggered manner. Fig.10 In addition to the arrangement shown, there may be other variations. Fig.11 The positions of the thick and thin lines shown are stamped twice and staggered on both sides, which can also evenly distribute the stress on both sides of the lead frame and avoid deformation of the lead frame. Of course, there can be other changes in implementation. Fig.11In the lead frame, the thin line is where the first arc portion 51 is formed, and the thick line is where the first protrusion 52 is formed.

[0044] See also Figure 8 , 12 A second embodiment of the manufacturing method of the lead frame of the present invention is substantially the same as the first embodiment, except that: after stamping in step 72 of the second embodiment, the substrate 20 is then rolled up and transported to the second punch 62. In step 73, the substrate 20 is rolled up, and the second surface 4 of the substrate 20 faces upward and toward the second punch 621, so that the second punch 621 can also punch from the second surface 4 to the first surface 3. The second embodiment also performs two stampings from different surfaces of the substrate 20, so that the stress is evenly distributed on the first surface 3 and the second surface 4 of the lead frame, achieving a stress balance effect.

[0045] The above are merely embodiments of the present invention, but they cannot be used to limit the scope of the present invention. That is, any simple equivalent changes and modifications made according to the claims and the description of the present invention still fall within the scope of the present invention.

Claims

1. A lead frame, comprising: a pin group, a first surface and a second surface spaced apart from each other and defined by the pin group, and a through surface extending downward from the first surface to the second surface and defining a hollow space located next to the pin group, characterized in that: A plurality of first arc portions in an arc shape and a plurality of first protrusions which are staggered with the first arc portions and protrude upward are formed at the connection between the through surface and the first surface. A plurality of second arc portions in an arc shape and a plurality of second protrusions which are staggered with the second arc portions and protrude downward are formed at the connection between the through surface and the second surface. The positions of the second arc portions correspond to the first protrusions in upper and lower directions, and the positions of the second protrusions correspond to the first arc portions in upper and lower directions.

2. The lead frame according to claim 1, wherein: The pin group includes a plurality of inner pins, each inner pin having a first side and a second side opposite to each other, one of the first arc portions being formed above the first side, one of the second protrusions being formed below the first side, one of the first protrusions being formed above the second side, and one of the second arc portions being formed below the second side.

3. The lead frame according to claim 2, wherein: The pin group includes a plurality of outer pins corresponding to the inner pins respectively, each outer pin having a third side and a fourth side opposite to each other, one of the first arc portions being formed above the third side, one of the second protrusions being formed below the third side, one of the first protrusions being formed above the fourth side, and one of the second arc portions being formed below the fourth side.

4. A method for manufacturing a lead frame, used for manufacturing the lead frame as claimed in claim 1, characterized in that: The manufacturing method of the lead frame comprises: Step A: providing a substrate for making the lead frame, wherein the substrate has a first surface and a second surface spaced apart from each other; Step B: stamping from the first surface toward the second surface of the substrate to form a portion of the pin set; Step C: Punching from the second surface of the substrate toward the first surface to form the rest of the pin set.

5. The method for manufacturing a lead frame according to claim 4, wherein: The manufacturing method of the lead frame is suitable for being carried out in conjunction with a first punching machine and a second punching machine, wherein the first punching machine has a first punch and the second punching machine has a second punch. In step B, the substrate is passed through the first punching machine, the first surface of the substrate faces upward and toward the first punch, and the first punch punches from the first surface to the second surface. The substrate is then turned over and transported to the second punching machine. In step C, the second surface of the substrate faces upward and toward the second punch, and the second punch punches from the second surface to the first surface.

6. The method for manufacturing a lead frame according to claim 5, wherein: The punching process in step B, turning over the substrate, and the punching process in step C are continuous and uninterrupted processes.

7. The method for manufacturing a lead frame according to claim 4, wherein: The manufacturing method of the lead frame is suitable for being carried out in conjunction with a first punching machine and a second punching machine, wherein the first punching machine has a first punch and the second punching machine has a second punch. In step B, the substrate is passed through the first punching machine, the first surface of the substrate faces upward and toward the first punch, and the first punch punches from the first surface to the second surface. The substrate is then rolled up and transported to the second punching machine. In step C, the substrate is rolled up, the second surface of the substrate faces upward and toward the second punch, and the second punch punches from the second surface to the first surface.

8. The method for manufacturing a lead frame according to claim 4, wherein: The positions of stamping on the substrate in step B and step C are arranged alternately.

9. The method for manufacturing a lead frame according to claim 4, wherein: The pin set includes a plurality of inner pins and a plurality of outer pins corresponding to the inner and outer positions of the inner pins. Step B is stamping to form a portion of the inner pins and the outer pins, and step C is stamping to form the remaining portions of the inner pins and the outer pins.

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