Progressive die for forming lead frame through forward and reverse punching and punching process

Abstract

The invention discloses a progressive die for forming a lead frame through positive and negative punching and a punching process. (i) during die opening, a lower die discharging plate is arranged in a protruding mode so as to support a strip for forming the lead frame; (ii) during die assembly stamping, the upper die holder moves downwards, the second stripper plate firstly presses the lower die stripper plate to fix the strip, and then the upper die holder continuously moves downwards until the lower die stripper plate moves downwards to a lower limit to expose the lower convex die set; and then the upper die base continues to move downwards until the second discharging plate is located at the upper limit to expose the upper convex die set, punching is completed, drifting of a single-side chamfering material of a product is avoided, the phenomena of deformation, warping and deviation of the product are prevented, and the overall quality of the product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a progressive die, more particularly, to a progressive die and stamping process for making lead frame by positive and reverse punching. BACKGROUND

[0002] Lead frame packaging technology is the cornerstone of the semiconductor packaging industry. It originated from the fundamental needs of protection, connection and heat dissipation, and has evolved with the development of electronic equipment from large computers to micro portable devices. From the early T0, DIP to the modern QFP, QFN, SOP, the core structure (metal frame bearing chip and providing pin connection) has always remained unchanged, but continuous innovation and optimization have been made in materials, manufacturing process, pin design and packaging form. With its core advantages of maturity, reliability, low cost, good heat dissipation, etc., lead frame packaging will still be an indispensable important part of the semiconductor packaging market for a long time in the future, especially in cost-sensitive, medium-low complexity, power applications, etc.

[0003] The conventional thickness of lead frame: 0.1mm-5.0mm, the thickness of lead frame of some high-end packaging is 0.03mm-0.06mm;

[0004] And its technology itself is also developing in the direction of higher density, smaller size, and stronger heat dissipation capacity. Its "small features" are the inevitable requirement and core embodiment of the development of modern microelectronic packaging towards miniaturization, high density and high performance. High-density small features include positive and reverse micro-features such as chamfering, stepping, bending and blanking on the front and back surfaces. Multiple positive and reverse punching of high-density steps, bending and chamfering on ultra-thin copper materials is prone to cause lead frame product curling, twisting and deformation. SUMMARY

[0005] The first object of the present application is to provide a progressive die for making lead frame by positive and reverse punching, the front and back forming dies are punched and formed at the same time, which solves the problem of single-sided material drift of the product, prevents the product from deforming, warping and offsetting, and improves the overall quality of the product.

[0006] The above technical object of the present application is achieved by the following technical solution:

[0007] A progressive die for making lead frame by positive and reverse punching, comprising an upper die seat and a lower die seat, the upper die seat and the lower die seat are provided with a plurality of stamping units, the stamping unit comprises:

[0008] (a) a second stripper plate elastically sliding on the upper die seat, and an upper punch assembly fixed on the upper die seat, the upper punch assembly penetrates the second stripper plate;

[0009] (b) the lower die stripper plate of the lower die shoe elastically slides on the lower die shoe, and the lower punch set fixed on the lower die shoe penetrates the lower die stripper plate;

[0010] (c) the lower die stripper plate and the second stripper plate correspond to each other in up and down directions;

[0011] (d) wherein the upper punch set and the lower punch set each include at least one of a chamfer punch, a bending punch and a step punch.

[0012] (i) when the mold is opened, the lower die stripper plate is provided with a protrusion to support the strip material for forming the lead frame;

[0013] (ii) when the mold is closed and punched, the upper die shoe moves downward, the second stripper plate first presses the lower die stripper plate to fix the strip material, then the upper die shoe continuously moves downward until the lower die stripper plate moves to the lower limit position to expose the lower punch set, then the upper die shoe continues to move downward until the second stripper plate is at the upper limit position to expose the upper punch set to complete the punching.

[0014] Preferably, the upper punch set includes an upper die chamfer punch, and the lower punch set includes a lower die chamfer punch, a lower die step punch and a lower die bending punch.

[0015] Preferably, the punching unit further comprises: the first stripper plate and the third stripper plate elastically sliding on the upper die shoe, the first stripper plate and the third stripper plate being located on one side of the second stripper plate; the upper die blanking punch fixed on the upper die shoe, the upper die blanking punch being located on the first stripper plate or / and the third stripper plate; the lower die shoe being provided with a die fixing plate, the die fixing plate being provided with a lower die recess corresponding to the upper die blanking punch.

[0016] Preferably, the second stripper plate is provided with an upper die limiting plate insert matched with the lower die step punch.

[0017] Preferably, the first stripper plate, the second stripper plate and the third stripper plate are each fixed with an upper die force transmission rod elastically sliding on the upper die shoe, the upper die force transmission rod and the upper die shoe being provided with a blocking piece to limit each other from sliding off; the upper die shoe is provided with an upper die force transmission rod elastically pushing the first stripper plate, the second stripper plate and the third stripper plate downward; the lower die stripper plate is fixed with a lower die force transmission rod elastically sliding on the lower die shoe, the lower die force transmission rod and the lower die shoe being provided with a blocking piece to limit each other from sliding off; the lower die shoe is provided with a lower die force transmission rod elastically pushing the lower die stripper plate upward.

[0018] Preferably, the upper die shoe is fixed with an upper die limiting plate above the second stripper plate, and the upper die limiting plate and the second stripper plate have a limiting gap therebetween; when the mold is closed, the upper die limiting plate reaches the upper limit position when it is flat with the second stripper plate, and the upper punch set protrudes out of the second stripper plate to complete the chamfer forming on the front surface of the lead frame.

[0019] Preferably, the upper die holder is fixed with a lower die limiting plate, the lower die limiting plate is located below the lower die stripper plate, and a gap is formed between the lower die limiting plate and the lower die stripper plate; when the mold is closed, the lower die limiting plate and the lower die stripper plate are attached to achieve the lower limit, and the lower punch set extends out of the lower die limiting plate to complete the stamping forming of the back surface of the lead frame.

[0020] Preferably, the upper die holder and the lower die holder are provided with stamping positioning outer guide columns; the first stripper plate, the second stripper plate and the third stripper plate are provided with sliding positioning inner guide columns, the inner guide columns are vertically inserted into the mold plate of the lower die holder; the lower die stripper plate is sleeved with the lower die small guide column which is fixed to the lower die holder.

[0021] Preferably, the upper die holder and the lower die holder are provided with sixteen stamping units.

[0022] The second object of the present application is to provide a stamping process of a lead frame, the front forming and back forming dies are simultaneously stamping formed, the occurrence of product single-side chamfer material drift is solved, the generation of product deformation warping deviation phenomenon is prevented, and the overall quality of the product is improved.

[0023] A stamping process of a lead frame, the progressive die of claim is adopted, the front and back stamping are completed by single stamping action, and the specific steps are as follows:

[0024] Step one: the strip is sent into the progressive die through the leveler feeder, the lower die stripper plate is raised to support the strip, and the upper die holder is moved downward under the action force of the press; the second stripper plate is firstly pressed and moved downward with the lower die stripper plate;

[0025] Step two: back stamping, as the lower die stripper plate moves downward, the lower die step punch, the lower die chamfer punch and the lower die bending punch gradually emerge from the lower die stripper plate;

[0026] until the first stripper plate, the second stripper plate and the corresponding recessed plate are pressed to make the die in the clamping position, that is, the lower die stripper plate is located at the lower limit, and the lower die step punch, the lower die chamfer punch and the lower die bending punch complete the back chamfering, back bending and back step forming of the lead frame;

[0027] Step three: front stamping, after the clamping position, as the lower die stripper plate moves downward, the upper die blanking punch and the upper die chamfer punch continue to move downward to the lower limit, and the front blanking and front chamfering process of the strip are completed.

[0028] In summary, the present application has at least one of the following beneficial effects:

[0029] 1. The lead frame product has multiple units, such as 16 units, each unit contains multiple blanking, front chamfering, back step, back chamfering, back bending and other forming features, and all processes are concentrated on a set of dies, which greatly improves the production efficiency.

[0030] 2. The positive and negative forming molds are almost simultaneously stamping formed, which solves the occurrence of product single-side chamfer material drift, prevents the generation of product deformation warping deviation phenomenon, and improves the overall quality of the product.

[0031] 3. The upper and lower molds of the mold are both designed with force transmission pull rods and force transmission pieces, which ensure that the lead frame strip is pressed and unloaded stably and uniformly, and improves the stability of lead frame strip production. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structure schematic diagram of the progressive die in the embodiment;

[0033] Figure 2 is a structure schematic diagram of the mold at the position of the first unloading plate of the upper die seat in the embodiment;

[0034] Figure 3 is a structure schematic diagram of the mold corresponding to the positions of the first unloading plate and the lower mold unloading plate when the mold is opened in the embodiment;

[0035] Figure 4 is a structure schematic diagram of the second unloading plate and the lower mold unloading plate located at the clamping station in the embodiment;

[0036] Figure 5 is an upper limit schematic diagram when the second unloading plate and the upper die limiting plate are attached in the embodiment;

[0037] Figure 6 is a top view schematic diagram of the strip after being continuously stamped three times by the progressive die in the embodiment;

[0038] Figure 7 is Figure 6 a structure schematic diagram of a stamping unit in the embodiment in the formation of the lead frame;

[0039] Figure 8 is Figure 7 a sectional view at A-A in the embodiment;

[0040] Figure 9 is Figure 7 a sectional view at B-B in the embodiment.

[0041] In the drawings:

[0042] 1, upper die seat; 21, first unloading plate; 22, second unloading plate; 23, third unloading plate;

[0043] 3, concave mold fixed plate; 4, lower die seat;

[0044] 5, outer guide column; 6, upper die force transmission pull rod; 7, upper die force transmission rod; 8, upper die blanking punch; 9, inner guide column; 10, upper die limiting plate insert; 11, upper die chamfering punch; 12, upper die limiting plate;

[0045] 14, lower die concave die; 15, lower die force transmission pull rod; 16, lower die step punch; 17, lower die force transmission rod; 18, lower die chamfer punch; 19, lower die stripper plate; 20, lower die small guide column; 30, lower die bending punch; 31, lower die limiting plate;

[0046] 111, strip;

[0047] 101, reverse face step one; 102, reverse face chamfer; 103, front face chamfer; 105, reverse face bending; 106, front face punching hole. DETAILED DESCRIPTION

[0048] The application will be further described in detail below with reference to the accompanying drawings.

[0049] Embodiment 1, a progressive die for making a positive and negative punch forming lead frame, referring to Figure 1 , comprising an upper die seat 1 and a lower die seat 4, the upper die seat 1 and the lower die seat 4 are provided with a plurality of stamping units, in this embodiment, sixteen stamping units, the sixteen stamping units are arranged in two columns in the progressive die, each column contains eight equally spaced stamping units, the specific arrangement of the stamping units on the die is referred to Figure 6 The arrangement position of the strip 111 formed in the die;

[0050] The upper die seat 1 and the lower die seat 4 are also provided with other punching dies, which are located behind or in front of the stamping units; with the pulling of the strip, after the strip is completed by the sixteen stamping units, the strip is pulled into the next punching die, which belongs to the conventional setting in the progressive die, and will not be described in detail.

[0051] ①For the upper die seat, referring to Figure 1 , the stamping units arranged therein include: a stripper plate group elastically sliding on the upper die seat 1, the stripper plate group includes first, second and third stripper plates 21, 22 and 23 arranged in sequence; the first, second and third stripper plates 21, 22 and 23 are all connected to the upper die seat 1 through the upper die force transmission pull rod 6 connected thereto, and the connection modes are the same;

[0052] Taking the first stripper plate 21 as an example, the lower end of the upper die force transmission pull rod 6 is fixed on the first stripper plate 21 by a screw, and the upper end of the upper die force transmission pull rod 6 vertically slides in the upper slide hole one of the upper die seat 1, the upper slide hole one has a shoulder to limit the upper die force transmission pull rod 6 from sliding out, and a compressed upper spring one is installed in the upper slide hole one, which abuts against the upper end of the rod body of the upper die force transmission pull rod 6, and the function of the upper spring one is to reset the upper die force transmission pull rod 6 retracted into the upper slide hole one.

[0053] The first discharge plate 21, the second discharge plate 22 and the third discharge plate 23 all keep the downward movement tendency by the pushing force of the respective upper die force transmission rod 7.

[0054] Still taking the first discharge plate 21 as an example, the upper end of the upper die force transmission rod 7 slides in the slide hole two of the upper die seat 1, the slide hole two has a shoulder to limit the slide of the upper die force transmission rod 7, and the upper spring two in the compressed state is installed in the slide hole two and abuts against the upper end of the rod body of the upper die force transmission rod 7; under the action of the upper spring two, the lower end of the upper die force transmission rod 7 is supported on the upper surface of the first discharge plate 21, and a downward moving pushing force is given to the first discharge plate 21.

[0055] The stamping unit includes an upper punch assembly, the upper punch assembly corresponds to the second discharge plate 22 and slides in the second discharge plate 22, and the upper punch assembly includes an upper die chamfer punch 11, the upper die chamfer punch 11 is fixed in the upper die seat 1, and a punch part of the upper die chamfer punch can vertically enter and exit the second discharge plate 22.

[0056] Referring to Figure 1 and Figure 2 , the stamping unit includes an upper die blanking punch 8, the upper die blanking punch 8 has two upper die blanking punches respectively corresponding to the first discharge plate 21 and the third discharge plate 23 and sliding in the first discharge plate 21 and the third discharge plate 23, and the upper die blanking punch 8 can enter and exit the corresponding first discharge plate 21 and third discharge plate 23.

[0057] The stamping unit includes an upper die limiting plate 12, the upper die limiting plate 12 is fixed in the upper die seat 1;

[0058] The upper die limiting plate 12 is above the second discharge plate 22, and a limiting gap is provided between the upper die limiting plate 12 and the second discharge plate 22; when the upper die limiting plate 12 and the second discharge plate 22 are attached, it is an upper limiting station, and the upper die chamfer punch 11 completes the chamfer forming on the lead frame.

[0059] The stamping unit includes an upper die limiting plate insert 10, the upper die limiting plate insert 10 is installed in the second discharge plate 22, the insert is convenient to replace, and belongs to the conventional setting in the stamping die. The upper die limiting plate insert 10 and the lower die cooperate to form a stamping step.

[0060] In the open die state, the lower surfaces of the first discharge plate 21, the second discharge plate 22 and the third discharge plate 23 are at the same height position and are in a flat state.

[0061] ②For the lower die seat 4, referring to Figure 1 , the stamping unit includes two die fixed plates 3, the die fixed plates 3 are fixed in the lower die seat 4 by screws, the lower die punch 14 is installed in the die fixed plate 3, and the lower die punch 14 is located on both sides of the lower die discharge plate 19; the lower die punch 14 and the upper die blanking punch 8 cooperate to perform punching forming.

[0062] Referring to Figure 3, the stamping unit comprises a lower die stripper plate 19, and the lower die stripper plate 19 is screw-fixed with a lower die force transmission rod 15; the lower die seat 4 is provided with a lower sliding hole one, the lower sliding hole one is internally provided with a lower spring one, the lower end of the lower die force transmission rod 15 is slidable in the lower sliding hole one, the lower spring one supports the lower end of the lower die force transmission rod 15, and a blocking shoulder is arranged between the lower die force transmission rod 15 and the lower sliding hole one, so that the lower die force transmission rod 15 cannot slide out of the lower sliding hole one, and the highest position of the protrusion of the lower die stripper plate 19 is limited.

[0063] The stamping unit comprises a lower die force transmission rod 17, the lower die force transmission rod 17 upwardly pushes the lower die stripper plate 19, so that the lower die stripper plate 19 maintains a upwardly pushing movement trend.

[0064] The lower die seat 4 is provided with a lower sliding hole two, the lower sliding hole two is internally provided with a lower spring two, the lower die force transmission rod 17 is slidable in the lower sliding hole two, the lower spring two is in a compressed state and supports the lower end of the lower die force transmission rod 17, and the upper end of the lower die force transmission rod 17 supports the lower surface of the lower die stripper plate 19.

[0065] Referring to Figure 3 In the mold opening state, the lower die force transmission rod 17 pushes up the lower die stripper plate 19, so that the lower die stripper plate 19 protrudes from the two side die fixed plates 3, the height of the protrusion can be a height value between 0.1-2mm, such as a protrusion height of 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm or 0.9mm, etc., in the embodiment, the protrusion height is 0.2mm, and the protruded lower die stripper plate 19 supports the strip 111.

[0066] Referring to Figure 3 The stamping unit comprises a lower punch group, the lower punch group comprises a lower die step punch 16, a lower die chamfer punch 18 and a lower die bending punch 30, and the lower die step punch 16, the lower die chamfer punch 18 and the lower die bending punch 30 are screw-fixed on the lower die seat 4.

[0067] The lower die step punch 16, the lower die chamfer punch 18 and the lower die bending punch 30 are all slidably arranged in the lower die stripper plate 19; when the lower die stripper plate 19 moves downwardly, the lower die step punch 16, the lower die chamfer punch 18 and the lower die bending punch 30 gradually extend out of the lower die stripper plate 19 to perform reverse stamping.

[0068] The lower die step punch 16, the lower die chamfer punch 18 and the lower die stripper plate 19 are all fixed on the connecting plate.

[0069] The lower die seat 4 is fixed with a lower die limiting plate 31, the lower die limiting plate 31 is located below the lower die stripper plate 19, and a gap is formed between the lower die limiting plate 31 and the lower die stripper plate 19.

[0070] Referring to Figure 4When the lower die stripper plate 19 is in contact with the lower die limiting plate 31, the lower die limiting plate 31 reaches the lower limit, and the lower punch assembly extends out of the lower die limiting plate 31 to complete the stamping of the lead frame.

[0071] ③Referring to Figure 1 In order to increase the precision in the stamping process, multiple guide designs are performed, specifically, an outer guide column 5 for stamping positioning is arranged between the upper die seat 1 and the lower die seat 4, and the outer guide column 5 of the upper die seat 1 is positioned to slide in the guide cylinder of the lower die seat 4 when the upper die seat 1 and the lower die seat 4 are closed.

[0072] The first stripper plate 21, the second stripper plate 22 and the third stripper plate 23 all slide with an inner guide column 9, and the lower die seat 4 is provided with a guide cylinder into which the inner guide column 9 is inserted, and the inner guide column 9 and the guide cylinder of the lower die seat 4 are vertically inserted during the stamping process.

[0073] The lower die small guide column 20 slides in the lower die stripper plate 19, and the lower die small guide column 20 is fixed in the lower die seat 4, and the lower die stripper plate 19 is provided with a guide cylinder into which the lower die stripper plate 19 is vertically positioned and inserted; during the up-down movement of the lower die stripper plate 19, the lower die small guide column 20 plays a positioning and guiding role, so that the up-down movement precision of the lower die stripper plate 19 is improved.

[0074] ④When the stamping action is performed, the upper die seat 1 is driven by the press machine, and the upper die seat 1 synchronously moves downward with the first stripper plate 21, the second stripper plate 22 and the third stripper plate 23 which are flat on the lower surface, and since the lower die seat 4 remains relatively stationary, the protrusions of the lower die stripper plate 19 are arranged as Figure 3 ;

[0075] The second stripper plate 22 and the lower die stripper plate 19 preferentially contact and clamp the strip 111 downward, at this time, the elastic force received by the second stripper plate 22 is greater than the elastic force received by the lower die stripper plate 19, so that the second stripper plate 22 has a pushing effect on the lower die stripper plate 19 during the downward movement;

[0076] Therefore, as the lower die seat 4 further moves downward, the lower die stripper plate 19 moves to the lower limit, that is, the lower die stripper plate 19 abuts against the lower die limiting plate 31, at this time, the lower die stripper plate 19 is flat with the upper surface of the concave die fixed plate 3, and the first stripper plate 21 and the third stripper plate 23 clamp the strip 111 with the corresponding concave die fixed plate 3 as Figure 4 ;

[0077] Then, referring to Figure 5 The upper die seat 1 further moves downward, the second stripper plate 22 and the upper die limiting plate 12 are in contact, and the stamping action is performed, and the positive and negative stamping actions of the upper punch assembly, the lower punch assembly and the upper die blanking punch 8 are completed.

[0078] The lower die stripper plate 19 is provided with a set of stamping components matched with the upper punch set, and the second stripper plate 22 is provided with a set of stamping components matched with the lower punch set. The set of stamping components can be directly formed on the stripper plate or installed through the way of inserts.

[0079] It is known that the high-precision progressive die stamps up to thousands of times per minute. The embodiment 1 is suitable for the progressive die stamping 1000-2000 times per minute. For the stamping 2000 times per minute, that is, 0.03 seconds are needed for each stamping action, and the stamping action includes the opening and closing of the die. The closing of the die only takes half of the time of the stamping action, that is, 0.015 seconds to complete the positive and reverse stamping. The synchronous positive and reverse stamping is almost instantaneous, which prevents the warping and offset of the lead frame and the distortion of the edge curling when the upper punch set and the lower punch set are formed.

[0080] Embodiment 2, a stamping process of a lead frame, using the progressive die of embodiment 1, referring to Figure 1 、 Figures 6-9 , the specific steps are as follows:

[0081] Step one: the strip 111 is fed into the die through the leveler feeder;

[0082] Step two: the upper die holder 4 is driven to move down, and the protrusion of the lower die stripper plate 19 plays a supporting role on the strip 111, so that the second stripper plate 22 moves down in advance and presses the strip 111 with the lower die stripper plate 19;

[0083] Step three: reverse side stamping, the second stripper plate 22 and the lower die stripper plate 19 continue to move down, and as the lower die stripper plate 19 moves down, the lower die step punch 16, the lower die chamfer punch 18, and the lower die bending punch 30 are exposed from the lower die stripper plate 19 until the lower die stripper plate 19 abuts against the lower die limiting plate 31 to reach the lower limit position. The stamping of the chamfer, the step, and the bending of the lower punch set is completed. The stamping station of the lower punch set is also a clamping station, as shown in Figure 4 , and the shapes of the reverse side step 101, the reverse side chamfer 102, and the reverse side bending 105 are formed on the strip 111, referring to Figures 6-9 ;

[0084] In the clamping station shown in Figure 4 , the lower surfaces of the first stripper plate 21, the second stripper plate 22, and the third stripper plate 23 are located in the same plane, and the upper surfaces of the lower die stripper plate 19 and the two side lower die concave punches 14 are located in the same plane. The upper die and the lower die clamp the strip as a whole, so that the strip cannot be offset;

[0085] Step four: positive side stamping, the upper die holder 1 continues to move down until the second stripper plate 22 and the upper die limiting plate 12 are flat, that is, the upper limit position as shown in Figure 5As shown, the upper die blanking punch 8 of the first stripper plate 21 and the third stripper plate 23 completes the punching action, and the upper die chamfering punch 11 of the second stripper plate 22 completes the front chamfering action; refer to Figures 6-9 The front blanking hole 106 and the front chamfer 103 are formed on the strip 111.

[0086] Step five: open the mold, the upper die holder 1 is driven by the press to slide up to the highest point, the strip 111 of the lead frame continues to be fed into a set step distance by the leveler feeder, and then the next punching forming action is performed, and so on. In the whole punching forming process, the outer guide column 5, the inner guide column 9, and the lower die small guide column 20 always precisely guide the stripper plate, so that the upper die blanking punch 8, the upper die chamfering punch 11, the lower die step punch 16, the lower die chamfering punch 18, and the lower die bending punch 31 precisely punch and form.

[0087] Working principle: when the press is at the lowest point, the springs of the upper die force transmission pull rod 6, the upper die force transmission rod 7, the lower die force transmission pull rod 15, and the lower die force transmission rod 17 are all in a compressed state, and the front and back punching, chamfering, stepping, and bending forming features of the strip 111 of the lead frame have been completed. At this time, the upper die blanking punch 8, the upper die chamfering punch 11, the lower die step punch 16, and the lower die chamfering punch 18 are in close contact with the strip 111. When the press slide moves upward, the upper die holder 1 moves upward to open the mold, the springs of the upper die force transmission pull rod 6, the upper die force transmission rod 7, the lower die force transmission pull rod 15, and the lower die force transmission rod 17 change from a compressed state to a relaxed state, so that the second stripper plate 22 moves downward and the lower die stripper plate 19 moves upward. In the movement process of the lower die stripper plate 19, the strip 111 of the lead frame is pushed away from the upper die blanking punch 8, the upper die chamfering punch 11, the lower die step punch 16, and the lower die chamfering punch 18.

[0088] In summary, during the punching process, the punching action of the upper die holder 1 is completed instantaneously, and the front punching and the back punching are almost completed simultaneously in the single die closing process. That is, the front punching and the back punching complete the punching, chamfering, stepping, and bending forming features at the same time through the interaction of force during the pressing process of the press.

[0089] Example 3, a lead frame punching process, uses the progressive die of example 1, which is different from example 2 in that, referring to Figure 1 The upper die chamfering punch 11 and the lower die chamfering punch 18 are located on the front and back of the same position of the strip 111, and the upper die chamfering punch 11 and the lower die chamfering punch 18 are vertically corresponding to the upper and lower positions of the strip, so that the front and back chamfering forming can be completed at one position.

[0090] The above merely describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-described embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also be considered as falling within the protection scope of the present application.

Claims

1. A progressive die for forming a lead frame by forward and reverse stamping, comprising an upper die holder (1) and a lower die holder (4), wherein the upper die holder (1) and the lower die holder (4) are provided with multiple stamping units, characterized in that: The stamping unit includes: (a) A second unloading plate (22) that slides elastically on the upper mold base (1) and an upper punch assembly that is fixed on the upper mold base (1), the upper punch assembly passing through the sliding second unloading plate (22); (b) A lower die stripper plate (19) that slides elastically on the lower die base (4) and a lower punch assembly that is fixed on the lower die base (4), the lower punch assembly passing through the sliding lower die stripper plate (19); (c) The lower mold stripper plate (19) and the second stripper plate (22) are aligned vertically; (d) wherein the upper punch assembly and the lower punch assembly each include at least one of the following: a chamfering punch, a bending punch, and a step punch. (i) When the mold is opened, the lower mold strip plate (19) is raised to support the strip (111) used to form the lead frame; (ii) During die-cutting, the upper die holder (1) moves down, and the second stripper plate (22) first presses against the lower die stripper plate (19) to fix the strip (111). Then the upper die holder (1) continues to move down until the lower die stripper plate (19) moves down to the lower limit position to expose the lower punch assembly. Then the upper die holder (1) continues to move down until the second stripper plate (22) is at the upper limit position to expose the upper punch assembly and complete the die-cutting.

2. The progressive die for forming a lead frame by forward and reverse stamping according to claim 1, characterized in that: The upper punch assembly includes an upper chamfering punch (11); The lower die assembly includes a lower die chamfering punch (18), a lower die step punch (16), and a lower die bending punch (30).

3. The progressive die for forming a lead frame by forward and reverse stamping according to claim 2, characterized in that, The stamping unit also includes: The first stripper plate (21) and the third stripper plate (23) of the upper mold base (1) are elastically slidable, and the first stripper plate (21) and the third stripper plate (23) are both located on one side of the second stripper plate (22); The upper die punch (8) is fixed to the upper die holder (1), and the upper die punch (8) is located on the first stripper plate (21) and / or the third stripper plate (23). The lower die base (4) is provided with a die fixing plate (3), and the die fixing plate (3) is provided with a lower die die (14) that corresponds to the upper die punching punch (8).

4. The progressive die for forming a lead frame by forward and reverse stamping according to claim 2, characterized in that: The second unloading plate (22) is provided with an upper mold limiting plate insert (10) adapted to the lower mold step punch (16).

5. The progressive die for forming a lead frame by forward and reverse stamping according to claim 3, characterized in that: The first unloading plate (21), the second unloading plate (22) and the third unloading plate (23) are all fixed with upper mold force transmission rods (6) that slide on the upper mold base (1). There are partitions between the upper mold force transmission rods (6) and the upper mold base (1) to restrict them from slipping off each other. The upper mold base (1) is provided with an upper mold force transmission rod (7) that elastically pushes the first unloading plate (21), the second unloading plate (22) and the third unloading plate (23) downward; The lower mold unloading plate (19) is fixed with a lower mold force transmission rod (15) that slides on the lower mold base (4). A partition is provided between the lower mold force transmission rod (15) and the lower mold base (4) to restrict them from slipping off each other. The lower mold base (4) is provided with a lower mold force transmission rod (17) that elastically pushes the lower mold unloading plate (19) upward.

6. The progressive die for forming a lead frame by forward and reverse stamping according to claim 1, characterized in that: The upper mold base (1) is fixed with an upper mold limiting plate (12), which is above the second unloading plate (22), and there is a limiting gap between the upper mold limiting plate (12) and the second unloading plate (22). When the mold is closed, the upper mold limiting plate (12) and the second stripper plate (22) are aligned and the upper punch plate extends out of the second stripper plate (22) to complete the chamfering of the front of the lead frame.

7. The progressive die for forming a lead frame by forward and reverse stamping according to claim 1, 2, or 6, characterized in that: The upper mold base (4) is fixed with a lower mold limiting plate (31), which is located below the lower mold unloading plate (19). There is a gap between the lower mold limiting plate (31) and the lower mold unloading plate (19). When the mold is closed, the lower mold unloading plate (19) and the lower mold limiting plate (31) are in contact and reach the lower limit, and the lower punch assembly extends out of the lower mold limiting plate (31) to complete the reverse stamping of the lead frame.

8. The progressive die for forming a lead frame by forward and reverse stamping according to claim 3, characterized in that: An outer guide post (5) for stamping positioning is provided between the upper die holder (1) and the lower die holder (4); The first unloading plate (21), the second unloading plate (22) and the third unloading plate (23) are provided with sliding positioning inner guide pillars (9), and the inner guide pillars (9) and the template of the lower mold base (4) are vertically inserted; The lower mold unloading plate (19) is fitted with a sliding lower mold guide post (20), which is fixed to the lower mold base (4).

9. The progressive die for forming a lead frame by forward and reverse stamping according to claim 1, characterized in that: The upper die holder (1) and the lower die holder (4) are equipped with sixteen stamping units.

10. A stamping process for a lead frame, characterized in that, Using the progressive die of claim 3, the front and back stamping are completed in a single stamping action. The specific steps are as follows: Step 1: The strip (111) is fed into the progressive die through the feeder of the leveling machine. The lower die ejector plate (19) protrudes and supports the strip (111). The upper die holder (1) moves downward under the force of the press. The second ejector plate (23) presses the strip (111) down one step ahead of the lower die ejector plate (19). Step 2: Reverse punching. As the lower die stripper plate (19) moves down, the lower die step punch (16), the lower die chamfering punch (18), and the lower die bending punch (30) gradually emerge from the lower die stripper plate (19). Until the first stripper plate (21), the second stripper plate (22), and the corresponding die fixing plate (3) press the strip (111) to make the die in the clamping position, the clamping position is the lower die stripper plate (19) is in the lower limit position, the lower die step punch (16), the lower die chamfering punch (18), and the lower die bending punch (30) complete the reverse chamfering and reverse bending and reverse step forming of the lead frame; Step 3: Front punching. After clamping, as the lower die stripper plate (19) moves down, the upper die punching punch (8) and the upper die chamfering punch (11) continue to move down to the lower limit, thus completing the front punching and front chamfering process of the strip (111).

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