High density foot for small diodes

Abstract

The present application relates to the technical field of semiconductor processing, and particularly relates to a high-density foot support for small diodes, comprising a pin frame, a plurality of groups of base pins are arranged in the pin frame, the base pins are sequentially provided with an inside adjusting arc and a first bending arc in the direction from the chip mounting assembly to the pin frame. The adjusting arc and the first bending arc improve the damage of the electrical performance of the base pins caused by the bending of the base pins when the base pins are bent into seagull pins after protruding from the plastic package, thereby reducing the return loss of the diode chip in the high-frequency circuit, and the total impedance change of the base pins when penetrating is slow. The first bending arc completes the bending of the seagull pin by making the bending degree of the base pin slow first and then fast, to meet the small size requirement, and by ensuring the final curvature radius of the first bending arc, the problem of high-frequency return loss being difficult to optimize due to the conflict between the impedance mutation caused by the bending of the pin and the miniaturization requirement in the prior art is overcome.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and more particularly to a high-density bracket for small diodes. Background Technology

[0002] As the functional complexity of new energy vehicle electronic control modules, automotive-grade MCUs, and power management ICs continues to increase, the industry's requirements for the functional complexity of small diode chips are constantly rising. Not only are there requirements to increase the number of integrated units and gradually reduce the volume ratio, but also higher requirements are placed on the signal transmission quality under high-frequency conditions, namely the 40GHz band. In order to reduce their size, traditional small diode chips usually need to bend their pins into gull-shaped pins. However, with the development of small diode chips, the traditional gull-shaped pins are becoming increasingly difficult to meet the signal transmission quality requirements of small diode chips at high frequencies due to their high bending rate.

[0003] Chinese Patent Application Publication No. CN115910974A discloses a high-density semiconductor integrated circuit lead frame, which includes multiple lead frame units arranged parallel to each other in the longitudinal and transverse directions. Each lead frame unit includes a frame connecting rib, multiple lead pins, multiple lead ends, and multiple lead base islands. The outer ends of the multiple lead pins are all connected to the frame connecting ribs. The multiple lead ends and the multiple lead base islands are respectively installed on the inner ends of the multiple lead pins. The multiple lead ends and the multiple lead base islands are arranged opposite to each other, and a lead gap is formed between the multiple lead ends and the multiple lead base islands.

[0004] Therefore, the existing technology has at least the following problems: it mainly focuses on the high-density arrangement of pins, without considering the impact of density and size reduction on the quality of high-frequency signal transmission, which easily leads to poor return loss performance of the generated products in the high-frequency band; it does not realize that pins are not only geometric change points, but also key structures affecting the impedance change of the bending area, and does not consider the impact on impedance by solving the geometry of the bending itself; it lacks the design for allocating the bending rate of the gull-foot, and cannot apply differentiated design to different positions of the bending section according to impedance sensitivity. Summary of the Invention

[0005] To address this, the present invention provides a high-density bracket for small diodes, which overcomes the problem in the prior art where impedance abrupt changes due to pin bending and miniaturization requirements are conflicting, making it difficult to optimize high-frequency return loss by controlling the impedance change rate at each position of the pin bending section.

[0006] To achieve the above objectives, the present invention provides a high-density bracket for small diodes, comprising: The pin frame contains several groups of basic pins, and the basic pins in the same group are connected to several groups of staggered chip mounting components to mount small diode chips. The basic pins are provided with an inner adjustment arc and a first bending arc in sequence from the chip mounting assembly toward the pin frame; The adjustment arc is located inside the molded body during chip molding to introduce impedance offset in the base pin and improve the bonding force between the base pin and the molded body. The amount of impedance offset introduced in the base pin is determined based on the magnitude and direction of the impedance change caused by the dielectric constant jump when the base pin protrudes from the molded body. The first bending arc is located where the base pin protrudes from the molded body during chip molding, in order to constrain the impedance change rate of the base pin after final molding.

[0007] Furthermore, the adjustment arc is a continuous, smooth arc segment that is recessed downward relative to the corresponding chip mounting component, so as to exert downward bending resistance on the base pin together with the molding compound.

[0008] Furthermore, the radius of curvature of the first bending arc decreases monotonically with the distance the base pin protrudes from the plastic package, so that the peak value of the impedance change caused by the bending is offset from the peak value of the impedance change caused by the base pin protruding from the plastic package into the air.

[0009] Furthermore, the groove depth of the adjustment arc is determined based on the amount of impedance change generated when the base pin changes from the internal medium of the molding compound to the external environment, wherein the direction of the impedance change introduced by the adjustment arc is opposite to the direction of the impedance change caused by the change in the medium. The radius of curvature of the adjustment arc is determined based on the bending properties of the base pin material and the width of the base pin, so as to keep the adjustment arc in a continuous and smooth transition, thereby reducing stress concentration and impedance abrupt changes in the adjustment arc region.

[0010] Furthermore, the radius of curvature R2 of the first bent arc changes in accordance with: R2(s)=R start +(R end -R start )×[1-exp(λ×s / L)] / [1-exp(λ)] Where s represents the arc length coordinate extending outward along the centerline of the base pin, starting from the point where the base pin extends out of the molded surface; R start R is the radius of curvature of the first bending arc near the end of the molding compound; end L is the radius of curvature at the end of the first bend away from the encapsulated body; L is the total arc length of the first bend; λ is a curvature evolution coefficient greater than zero, which limits the direction of change of the radius of curvature along the arc length. R start R is greater than the minimum bending radius corresponding to the width of the base pin. endIt is greater than the minimum bending radius corresponding to the allowable bending deformation of the base pin material.

[0011] Furthermore, it also includes a first stacked bracket with the same positioning hole as the pin frame, which is provided with a stabilizing pin corresponding to the base pin on the same side and in the same group as the corresponding molding body. The stabilizing pin is provided with a reinforcing strip at the adjustment arc groove of the base pin on the same side and in the same group as the corresponding molding body, so as to form an interlocking structure with the adjustment arc in the corresponding molding body.

[0012] Furthermore, the reinforcing strip includes symmetrically distributed reinforcing ribs, with limiting plates disposed between the symmetrical reinforcing ribs. The reinforcing ribs are used to bend the limiting plates and bend the limiting plates into an arc similar to the adjustment arc.

[0013] Furthermore, the coefficient of thermal expansion of the reinforcing strip is the same as that of the base pin, and it does not contact the adjacent adjustment arc.

[0014] Furthermore, it also includes a second stacked bracket with the same positioning hole as the pin frame, which is provided with an auxiliary pin corresponding to the base pin on the same side of the pin frame. The auxiliary pin is provided with a limiting strip in the bending direction of the first bending arc of the base pin on the same side of the corresponding pin frame. The limiting strip is used to provide gradual limiting support for the first bending arc during the bending process of the base pin, so as to limit the rate of change of the curvature radius of the first bending arc.

[0015] Furthermore, the limiting strip is elastic, and its thickness gradually decreases as the base pin protrudes from the encapsulation.

[0016] Compared with the prior art, the beneficial effects of the present invention are that it improves the electrical performance of the base pin caused by bending into a seagull-like shape after the base pin protrudes from the molded body through the adjustment arc and the first bending arc, thereby reducing the return loss of the diode chip in high-frequency circuits. The adjustment arc is located inside the molded body. On the one hand, it introduces an impedance offset opposite to the impedance change caused by the subsequent dielectric constant jump before the pin protrudes from the molded body, thus slowing down the total impedance change when the base pin protrudes. On the other hand, this recess increases the contact area between the base pin and the molded body without changing the cross-sectional structure of the base pin itself, improving the bonding force between the two without causing a sudden change in electrical performance. The first bending arc is located where the pin protrudes from the molded body, i.e., the uppermost bend of the seagull-like shape. By limiting the initial curvature at the root of the first bending arc... The radius of curvature is designed to ensure a smooth start at the root of the first bending arc without introducing a significant impedance change. This reduces the overlap between the abrupt change in dielectric constant after the base pin protrudes from the molded enclosure and the impedance change introduced by the first bending arc. During subsequent bending processes, the radius of curvature monotonically decreases along the arc length, resulting in a slow-to-faster bending trend to complete the seagull-foot bend. This meets the small size requirements of miniaturized diode chips. Simultaneously, by ensuring that the final radius of curvature of the first bending arc, i.e., its minimum radius of curvature, still meets the impedance change rate requirement, the impedance change rate throughout the entire bending process remains within a controllable range. The two arc segments are geometrically connected sequentially, strictly controlling the impedance characteristics of the base pin along the entire path from the inside of the molded enclosure to the external solder surface from different angles. This reduces the high-frequency return loss of the diode chip, thereby increasing the circuit stability performance of the diode chip. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the high-density bracket for small diodes as described in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the adjustment arc, the first bending arc, and the second bending arc according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the first stacked bracket and stabilizing pin in an embodiment of the present invention; Figure 4 This is a schematic diagram of the reinforcing ribs and limiting plates in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the adjusting arc and the limiting piece in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the second overlapping leg and the limiting strip in an embodiment of the present invention.

[0018] The attached figures are labeled as follows: 1-pin frame, 11-basic pin, 101-chip carrier platform, 102-solder pin, 103-adjustment arc, 104-first bending arc, 105-second bending arc, 2-molded body, 3-first stacked bracket, 31-stabilizing pin, 301-reinforcing rib, 302-limiting piece, 4-second stacked bracket, 41-auxiliary pin, 401-limiting strip. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper," "lower," "inner," "outer," etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figures 1-5 As shown, a high-density bracket for small diodes includes: The pin frame 1 has several groups of basic pins 11 inside, and several groups of staggered chip mounting components are arranged on the basic pins 11 in the same group to mount small diode chips.

[0024] The chip mounting assembly includes a chip mounting stage 101 and solder joint pins 102, wherein each chip mounting stage 101 and solder joint pin 102 is connected to only one base pin 11.

[0025] The basic pin 11 is provided with an inner adjustment arc 103, a first bending arc 104 and a second bending arc 105 in sequence from the chip mounting assembly toward the pin frame 1.

[0026] The adjustment arc 103 is located inside the molded body 2 during chip molding to introduce impedance offset in the base pin 11 and improve the bonding force between the base pin 11 and the molded body. The offset amount of the impedance offset introduced in the base pin 11 is determined based on the amplitude and direction of the impedance change caused by the dielectric constant jump when the base pin 11 protrudes from the molded body.

[0027] The first bending arc 104 is located at the point where the base pin 11 protrudes from the mold body 2 during chip molding, in order to constrain the impedance change rate of the base pin 11 after final molding.

[0028] The second bending arc 105 is located near the lower surface of the base pin 11 close to the molded body 2, so that the base pin 11 bends to a vertical state after being bent by the first bending arc 104 and then bends back to a horizontal state. The change range and direction of the curvature radius of the second bending arc 105 are opposite to the change range and direction of the curvature radius of the first bending arc 104 along the extension direction of the base pin 11 after it protrudes from the molded body 2.

[0029] Please see Figure 2 As shown, in this embodiment, the adjustment arc 103 is a continuous smooth arc segment that is recessed downward relative to the corresponding chip mounting component. Together with the molding compound 2, it applies downward resistance to the base pin 11 as it bends downward after protruding from the molding compound 2, thereby reducing the probability that the pin inside the molding compound 2 will be pulled out or lifted upward.

[0030] In this embodiment, the radius of curvature of the first bending arc 104 decreases monotonically with the distance the base pin 11 protrudes from the plastic package 2, so that the peak value of the impedance change caused by bending is staggered from the peak value of the impedance change caused by the base pin 11 protruding from the plastic package into the air, thereby increasing the stability of the electrical performance of the base pin 11 by reducing the amplitude of the impedance change fluctuation of the base pin 11.

[0031] Specifically, this invention improves the electrical performance of the base pin caused by its bending into a seagull-like shape after protruding from the molded enclosure by adjusting the arc and the first bending arc, thereby reducing the return loss of the diode chip in high-frequency circuits. The adjusting arc is located inside the molded enclosure. On one hand, it introduces an impedance offset opposite to the impedance change caused by subsequent dielectric constant jumps before the pin protrudes from the enclosure, thus slowing down the overall impedance change when the base pin emerges. On the other hand, this recess increases the contact area between the base pin and the molded enclosure without altering the base pin's structure, improving the bonding force while reducing the probability of significant structural changes in the base pin that could cause a sudden change in electrical performance. The first bending arc is located where the pin protrudes from the molded enclosure, at the uppermost bend of the seagull-like shape. By limiting the initial... The radius of curvature is designed to ensure a smooth start at the root of the first bending arc without introducing a significant impedance change. This reduces the overlap between the abrupt change in dielectric constant after the base pin protrudes from the molded enclosure and the impedance change introduced by the first bending arc. During subsequent bending processes, the radius of curvature monotonically decreases along the arc length, resulting in a slow-to-fast evolution of the bending to complete the seagull-foot bend. This meets the small size requirements of miniaturized diode chips. Simultaneously, by ensuring that the final radius of curvature of the first bending arc, i.e., its minimum radius of curvature, is still limited by the rate of impedance change, the rate of impedance change throughout the bending process remains within a controllable range. The two arc segments are geometrically connected sequentially, strictly controlling the impedance change of the base pin along the entire path from the inside of the molded enclosure to the external solder surface from different angles. This reduces the high-frequency return loss of the diode chip, thereby increasing the circuit stability of the diode chip.

[0032] In this embodiment, the groove depth of the adjustment arc is determined based on the amount of impedance change generated when the base pin changes from the internal medium of the molding compound to the external environment. The direction of the impedance change introduced by the adjustment arc is opposite to the direction of the impedance change caused by the change in the medium.

[0033] The radius of curvature of the adjustment arc is determined based on the bending properties of the base pin material and the width of the base pin, so as to keep the adjustment arc in a continuous and smooth transition, thereby reducing stress concentration and impedance abrupt changes in the adjustment arc region.

[0034] In this embodiment, for example, the maximum groove depth Δh and the minimum radius of curvature R1 of the groove in the adjustment arc 103 are defined by the following parametric equations: Δh=min[Δh3,max(Δh1,Δh2)] Where Δh1 is the theoretical compensation depth; Δh2 is the minimum depth of the groove; and Δh3 is the maximum depth of the groove.

[0035] Δh1=[Z0(ε r =ε air Hair )-Z0(ε r =ε mold H mold )] / ( Z0 / H) Wherein, Z0(ε r =ε air H air The relative permittivity ε of the base pin 11 in external air r =air, vertical distance H from base pin 11 to the reference ground plane air The characteristic impedance is determined by the width W and thickness T of the base pin 11; Z0(ε r =ε mold H mold The relative permittivity ε of the base pin 11 inside the plastic package r =ε mold The vertical distance H from the base pin 11 to the reference ground plane mold Characteristic impedance of the width W and thickness T of the basic pin 11; Z0 / H is the partial derivative of the characteristic impedance Z0 with respect to the distance H from the base pin 11 to the reference ground plane, derived from the microstrip line impedance formula.

[0036] In this embodiment, Z0(ε) r =ε air H air ) and Z0(ε r =ε mold H mold All of these are determined by substituting the relative permittivity at the corresponding position and the vertical distance from the base pin 11 to the reference ground plane into the microstrip line characteristic impedance formula.

[0037] In this embodiment, the reference ground plane is a conductive plane with a constant potential that together with the signal conductor, i.e., the basic pin 11, forms a transmission line structure. It is determined based on the IPC-2141A "Controlled Impedance Circuit Board Design Guide" standard.

[0038] In this embodiment, in addition to meeting the impedance compensation requirements caused by changes in dielectric constant, the adjustment arc 103 is also used to alleviate the interface stress caused by the difference in thermal expansion between the molding compound 2 and the base pin 11. Therefore, it is also necessary to determine the minimum groove depth Δh2 that meets the mechanical bonding requirements. The minimum groove depth Δh2 of the adjustment arc 103 is based on the thermal expansion mismatch ΔX. exp The value is determined and increases with the increase of thermal expansion mismatch, so that the mechanical interlock structure formed by the adjusting arc 103 absorbs the relative displacement caused by the thermal expansion difference between the molding compound 2 and the base pin 11, reducing the risk of interface shear separation. The thermal expansion mismatch ΔX is specified.exp satisfy: ΔX exp =L CTE ×ΔT cure ×|α EMC -α Lead | Among them, L CTE To adjust the horizontal coupling length of arc 103; ΔT cure The temperature difference between the curing temperature of the molding compound 2 and room temperature; α EMC α is the coefficient of thermal expansion of the molding compound 2; Lead The coefficient of thermal expansion of the base pin 11.

[0039] In this embodiment, the maximum depth Δh3 of the groove of the adjustment arc 103 is determined based on the thickness T of the base pin 11 and increases with the increase of the thickness T of the base pin 11, so as to ensure that the size of the adjustment arc 103 will not cause an additional increase in the size of the small diode chip, i.e., the plastic package 2, in order to meet the miniaturization requirements of the small diode chip.

[0040] R1≥max[E×T / (2σ Y ), w1] Where R1 is the radius of curvature of the adjustment arc 103; E is the Young's modulus of the base pin 11 material; T is the thickness of the base pin 11; σ Y The yield strength of the base pin 11; w1 is the minimum radius of curvature, which is determined based on the width W of the base pin 11 and the three-times-linewidth criterion to limit the minimum value of the radius of curvature of the adjustment arc 103.

[0041] Specifically, this invention determines the theoretical maximum depth of the adjustment arc by compensating for dielectric constant jumps. Simultaneously, it supplements and raises the determined base value by absorbing thermal expansion mismatch to ensure that the interface does not separate during temperature changes. Furthermore, it truncates the determined maximum depth by controlling the pin cross-sectional strength to ensure that the groove depth does not exceed the safe range allowed by the pin thickness. Ultimately, the adjustment arc introduces impedance in the opposite direction to the impedance change caused by dielectric variations. This compensates for impedance abrupt changes caused by dielectric constant jumps when the pin protrudes from the encapsulation, reducing signal reflection losses at high frequencies. On the other hand, a mechanical interlock structure is formed between the groove and the encapsulation to resist the force that would cause the base pin to separate from the encapsulation. Simultaneously, by controlling the radius of curvature at the bottom of the groove to be no less than the minimum value determined by material strength and sharp bend reflection suppression, the probability of the adjustment arc itself becoming a stress concentration source or introducing additional signal reflection sources into the electrical signal due to an excessively small radius of curvature is reduced.

[0042] In this embodiment, the variation law of the radius of curvature R2 of the first bending arc satisfies: R2(s)=Rstart +(R end -R start )×[1-exp(λ×s / L)] / [1-exp(λ)] Where s is the arc length coordinate extending outward from the point where the base pin 11 extends outward from the surface of the molding compound 2; R start The base pin 11 extends from the root of the molding compound 2, i.e., the initial radius of curvature R2 at s=0; R end Let be the terminating radius of curvature s=L at the end of the first bent arc 104; L be the total arc length of the first bent arc 104; λ be a curvature evolution coefficient greater than zero, which is based on R. start R end L is determined to limit the rate of change of the radius of curvature of the first bend along the arc length direction, so that the degree of bending of the first bend evolves in a slow-to-fast manner, and the return loss generated by the first bend during the bending process is reduced.

[0043] R start R is greater than the minimum bending radius corresponding to the width of the base pin. end It is greater than the minimum bending radius corresponding to the allowable bending deformation of the base pin material.

[0044] In this embodiment, for example, R start and R end They respectively satisfy the following rules: R start ≥w1 R end ≥max[E×T / (2×σ Y ), w1] Where E is the Young's modulus of the base pin material; T is the base pin thickness; σ Y w1 is the yield strength of the material of the base pin 11, and w1 is the minimum radius of curvature.

[0045] | Z0 / H|×sin(θ(s))≤K refl ×Z0 / Λ eff , θ(s)≤θ limit ; Where θ(s) is the cumulative bending angle from the starting point of the first bend arc to position s, θ(s) = u is the integral variable, representing the infinitesimal arc length element from the starting point to the current position s; R2 is the radius of curvature of the first bend arc; θ limit The maximum cutoff angle to which the microstrip line impedance formula applies; Z0 is the characteristic impedance of the base pin; Λ eff Λ is the effective wavelength in the medium containing the first bent arc. eff =c / (f× ), where ε eff K is the effective dielectric constant of the medium, c is the speed of light in vacuum, f is the target frequency of the diode chip where the basic pin 11 is located; refl K is the reflection tolerance coefficient determined by the target return loss, and K is the proportionality coefficient of the maximum allowable rate of change of impedance to the ratio of characteristic impedance to effective wavelength. refl =2×Γ max , Γ max To achieve the maximum allowable voltage reflection coefficient for the target return loss, Γ max = RL is the absolute value of the return loss of the target; Z0 / H is the partial derivative of the characteristic impedance Z0 with respect to the distance H from the base pin 11 to the reference ground plane, derived from the microstrip line impedance formula.

[0046] Specifically, this invention takes into account that the root region closest to the molding compound has the strongest coupling with the reference ground plane and is most sensitive to attitude changes in impedance. By designing the first bending arc as a variable curvature arc with a gentle start and gradually accelerating as the extension length increases, the bending process in the initial stage is made as gentle as possible, reducing interference to the electrical signal state after impedance compensation when the base pin protrudes from the molding compound. Subsequently, in the subsequent bending process, based on electrical requirements and limited bending space, the bending speed of the first bending arc is uniformly increased, thereby increasing the bending rate of the base pin to complete the gull-foot shape as quickly as possible. The bending process is designed to meet the size requirements of the diode chip and to evenly distribute the impedance change caused by bending across the entire arc length. This ensures that the impedance change of the first bending arc does not disrupt the established impedance continuity. After bending, there are no significant impedance abrupt changes in the high-frequency signal path, thereby reducing the overall return loss during the bending process of the plastic package at the base pin protrusion in the 40GHz high-frequency band. During the bending process of the first bending arc, its radius of curvature is always limited by local stress and electrical performance to avoid breakage or strong local reflection at the most severe bending point.

[0047] Please see Figures 3-5 As shown, in this embodiment, a first stacked bracket 3 with the same positioning hole as the pin frame 1 is also included, which is provided with a stable pin 31 corresponding to the base pin 11 on the same side and in the same group as the corresponding molding body 2; The stabilizing pin 31 is provided with a reinforcing strip at the groove of the adjustment arc 103 of the base pin 11 on the same side and in the same group as the corresponding molding compound 2, so as to form an interlocking structure with the adjustment arc 103 in the corresponding molding compound 2. The coefficient of thermal expansion of the reinforcing strip is the same as that of the base pin 11, and it does not contact the adjacent adjustment arc 103. The two are kept at a distance to reduce the probability of the reinforcing strip affecting the electromagnetic environment around the adjustment arc 103, so as to avoid introducing new electrical performance interference to the base pin 11. Both the reinforcing strip and the base pin 11 are cut off on the molding compound 2.

[0048] During the soldering process on the outside of the base pin, the adjustment arc 103 clamps the molding compound material when it begins to expand due to heat by maintaining a similar coefficient of thermal expansion to the base pin 11, thereby increasing the bonding force between the molding compound 2 and the base pin 11 and increasing the moisture resistance between the molding compound 2 and the base pin 11.

[0049] In this embodiment, the reinforcing strip includes symmetrically distributed reinforcing ribs 301, and limiting pieces 302 are provided between the symmetrical reinforcing ribs 301. The limiting pieces 302 are flexible parts. The reinforcing ribs 301 are used to bend the limiting pieces 302 and bend the limiting pieces 302 into an arc similar to the adjustment arc 103. The distance between the limiting piece 302 on the side closer to the chip mounting assembly and the base pin 11 is greater than the distance between the limiting piece 302 on the side farther from the chip mounting assembly and the base pin 11, so as to ensure that the material of the molding compound smoothly enters the gap between the limiting piece 302 and the base pin 11 during the molding process.

[0050] Specifically, this invention increases the bonding force of the mechanical locking structure between the adjusting arc and the molding compound by spatially coordinating the reinforcing strip and the adjusting arc groove within the molding compound. This allows the adjusting arc to focus more on improving electrical performance rather than prioritizing its bonding force with the molding compound, thus providing conditions for better electrical performance. Simultaneously, the molding compound between the reinforcing strip and the adjusting arc acts as a force and heat transfer medium. Not only is the pull-out force on the base pin shared by the compressive strength of the molding compound and the bonding locking force between the reinforcing strip and the molding compound, but the pull-out resistance of the base pin is significantly improved, reducing the probability of the base pin being pulled out during bending and cutting. Furthermore, by maintaining similar thermal expansion between the base pin and the reinforcing strip at the high temperature of reflow soldering, the molding compound sandwiched between them is compressed more tightly at high temperatures rather than expanding and loosening, thereby reducing the probability of moisture absorption and interface separation between the two.

[0051] Please see Figure 5 and Figure 6As shown, in this embodiment, a second stacked bracket 4 with the same positioning hole as the pin frame 1 is also included. It is provided with an auxiliary pin 41 corresponding to the base pin 11 on the same side as the pin frame 1. The auxiliary pin 41 is provided with a limiting strip 401 in the bending direction of the first bending arc 104 of the base pin 11 on the same side as the corresponding pin frame 1. The limiting strip is used to provide gradual limiting support for the first bending arc during the bending process of the base pin, so as to limit the rate of change of the curvature radius of the first bending arc 104. The limiting strip 401 is attached to the encapsulation body 2.

[0052] In this embodiment, the limiting strip 401 is elastic, and the thickness of the limiting strip 401 gradually decreases as the base pin 11 protrudes from the encapsulation 2. This causes the supporting limiting force provided by the limiting strip 401 to the base pin 11 to gradually decrease as the radius of curvature of the first bending arc 104 decreases. This ensures that the bending path of the first bending arc 104 meets the design requirements while reducing the probability of the first bending arc 104 being indented due to hard compression limiting.

[0053] Specifically, this invention utilizes a second overlapping bracket, which is attached to the lead frame during the cutting process. This allows a limiting strip attached to the molding compound to provide an elastic limiting force that gradually weakens as the lead extension length increases during the bending process of the first bending arc. This provides strong limiting support for the first bending arc near the molding compound, while gradually releasing bending freedom further away from the molding compound. This guides the base lead to complete the bending along a preset radius of curvature change trajectory, avoiding abrupt changes in the radius of curvature in local areas due to cutting impact. It also effectively reduces the cost of improving existing cutting blades and ensures that the actual formed base lead meets the electrical performance requirements of the design. At the same time, the gradual elasticity of the limiting strip reduces surface damage to the base lead caused by hard extrusion, preventing the formation of indentations or stress concentration points on the signal transmission path. This reduces the probability of introducing additional impedance discontinuities due to surface defects under high-frequency skin effect, ensuring that the designed curvature of the first bending arc can be stably reproduced during the manufacturing stage.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-density bracket for small diodes, characterized in that, include: The pin frame contains several groups of basic pins, and the basic pins in the same group are connected to several groups of staggered chip mounting components to mount small diode chips. The basic pins are provided with an inner adjustment arc and a first bending arc in sequence from the chip mounting assembly toward the pin frame; The adjustment arc is located inside the molded body during chip molding to introduce impedance offset in the base pin and improve the bonding force between the base pin and the molded body. The amount of impedance offset introduced in the base pin is determined based on the impedance change caused by the dielectric constant jump when the base pin protrudes from the molded body. The first bending arc is located where the base pin protrudes from the molded body during chip molding, in order to constrain the impedance change rate of the base pin after final molding.

2. The high-density bracket for small diodes according to claim 1, characterized in that, The adjustment arc is a continuous, smooth arc segment that is recessed downward relative to the corresponding chip mounting component to exert downward bending resistance on the base pin together with the molding compound.

3. The high-density bracket for small diodes according to claim 1, characterized in that, The radius of curvature of the first bending arc decreases monotonically with the distance the base pin protrudes from the plastic package, so that the peak value of the impedance change caused by the bending is offset from the peak value of the impedance change caused by the base pin protruding from the plastic package into the air.

4. The high-density bracket for small diodes according to claim 1, characterized in that, The groove depth of the adjustment arc is determined based on the amount of impedance change generated when the base pin changes from the internal medium of the plastic package to the external environment. The direction of the impedance change introduced by the adjustment arc is opposite to the direction of the impedance change caused by the change in the medium. The radius of curvature of the adjustment arc is determined based on the bending properties of the base pin material and the width of the base pin, so as to keep the adjustment arc in a continuous and smooth transition, thereby reducing stress concentration and impedance abrupt changes in the adjustment arc region.

5. The high-density bracket for small diodes according to claim 3, characterized in that, The variation law of the radius of curvature R2 of the first bend arc satisfies: R2(s)=R start +(R end -R start )×[1-exp(λ×s / L)] / [1-exp(λ)] Where s represents the arc length coordinate extending outward along the centerline of the base pin, starting from the point where the base pin extends out of the molded surface; R start R is the radius of curvature of the first bending arc near the end of the molding compound; end L is the radius of curvature at the end of the first bend away from the encapsulated body; L is the total arc length of the first bend; λ is a curvature evolution coefficient greater than zero, which limits the direction of change of the radius of curvature along the arc length. R start R is greater than the minimum bending radius corresponding to the width of the base pin. end It is greater than the minimum bending radius corresponding to the allowable bending deformation of the base pin material.

6. The high-density bracket for small diodes according to claim 1, characterized in that, It also includes a first stacked bracket with the same positioning hole as the pin frame, which is provided with a stabilizing pin corresponding to the base pin on the same side and in the same group as the corresponding molding body. The stabilizing pin is provided with a reinforcing strip at the adjustment arc groove of the base pin on the same side and in the same group as the corresponding molding body, so as to form an interlocking structure with the adjustment arc in the corresponding molding body.

7. The high-density bracket for small diodes according to claim 6, characterized in that, The reinforcing strip includes symmetrically distributed reinforcing ribs, with limiting plates placed between the symmetrical reinforcing ribs. The reinforcing ribs are used to bend the limiting plates and bend them into an arc similar to the adjustment arc.

8. The high-density bracket for small diodes according to claim 6, characterized in that, The coefficient of thermal expansion of the reinforcing strip is the same as that of the base pin, and it does not contact the adjacent adjustment arc.

9. The high-density bracket for small diodes according to claim 1, characterized in that, It also includes a second stacked bracket with the same positioning hole as the pin frame. It is provided with an auxiliary pin corresponding to the base pin on the same side of the pin frame. The auxiliary pin is provided with a limiting strip in the bending direction of the first bending arc of the base pin on the same side of the corresponding pin frame. The limiting strip is used to provide gradual limiting support for the first bending arc during the bending process of the base pin, so as to limit the rate of change of the curvature radius of the first bending arc.

10. The high-density bracket for small diodes according to claim 9, characterized in that, The limiting strip is elastic, and its thickness gradually decreases as the base pin protrudes from the plastic package.

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