Shrinkage type top heat dissipation reverse forming packaging structure and processing technology thereof

Abstract

The invention relates to the field of digital power amplifier circuit IC packaging application, in particular to a contraction type top heat dissipation type reverse forming packaging structure and a processing technology thereof.The packaging structure is provided with a lead frame packaging structure large base island for bearing a large-size digital power amplifier chip, and base island mutual fusion type double-connecting-rib structures are arranged on the left side and the right side of the lead frame base island for bearing the large-size digital power amplifier chip; the tail ends of the double connecting ribs on the left side and the right side are respectively provided with a fishtail shape to be communicated with the lead frame body, and the RDL metal bonding pads on the surface of the chip are electrically connected with the pins in the lead frame in a large-wire-diameter and multi-bonding-wire mode. According to the packaging structure, heat dissipation of a high-power product is facilitated, diffusion of bonding glue on the front face of a product base island and plastic packaging materials on the back face of the product base island is blocked, therefore, the quality and reliability of the product are guaranteed and improved, meanwhile, the packaging strength and coplanarity of the whole packaging structure are guaranteed and improved, and the product quality and reliability of the packaging structure are further improved.

Description

Technical Field

[0001] The invention relates to the application field of digital power amplifier circuit IC packaging, in particular to a shrinkage type top heat dissipation reverse forming packaging structure and a processing technology thereof. Background Art

[0002] The main function of traditional power amplifiers is to amplify power. The functions are not very different. The main differences are indicators such as power, distortion, signal-to-noise ratio, and controllability. Due to the limitation of volume, the output power of the entire power amplifier circuit is limited, the dynamic range is small, and a single channel is only about 10-40W. There are defects such as single function and unadjustable sound field. When working, traditional power amplifiers will consume more power as heat. The entire power amplifier circuit has problems such as heating, noise, poor sound quality, and low working efficiency. At low levels, the opening and closing of positive and negative channels often produce crossover distortion.

[0003] New energy vehicles are paying more and more attention to the audio experience of smart cockpits. High-power amplifiers, Dolby audio, and panoramic sound have gradually entered the automotive field. The design of ultra-multi-channel and ultra-large amplifiers has subverted the traditional car audio design. In particular, with the rapid development of digital amplifier technology, high-power, multi-channel, and high-performance amplifier systems have made mobile theaters, karaoke halls, and HIFI audio possible in cars; with the breakthrough of digital amplifier technology, digital amplifiers have become the mainstream technology of new energy vehicles; digital amplifiers are different from traditional amplifiers. They are amplifiers of working switching signals, with high switching frequency, high efficiency, high performance, high power, high dynamics, ultra-high linearity, and ultra-low distortion amplifier technology. At present, the automotive industry has a huge market, and car audio will be a must-fight place for many audio manufacturers. With the vigorous development of new energy vehicles, car audio will have a larger market development space, bringing opportunities for emerging car audio. At the same time, with the continued rapid development of China's economy, the demand for automobiles will increase, bringing new opportunities for the development of car audio. In the future, digital amplifiers will be more widely used in the field of car audio.

[0004] UeSSOP56L (Shrink Small Outline Package (Up exposed thermal paddle)) shrink-type top heat dissipation reverse forming IC packaging technology is a new SMT technology (surface mount technology) with exposed heat sink (upward). There is no UeSSOP56L package in the market. The similar T / SSOP48L package does not have a heat sink. The product heat dissipation is far from meeting customer product needs. The product's anti-interference and harsh environment adaptability, AM / FM reception sensitivity, dynamic range, product output power, impedance, current linearity, saturation voltage drop, efficiency, and overheating short circuit protection do not meet automotive grade requirements. Based on this, technological innovation is needed to develop new products and corresponding packaging processes to solve existing problems and improve product quality and scope of use. Summary of the invention

[0005] In view of the problem that the heat dissipation performance, anti-interference, harsh environment adaptability, electrical performance and other aspects of T / SSOP48L packaging products in the prior art cannot meet the automotive-grade requirements without a heat sink, the present invention provides a shrinkable top heat dissipation reverse forming packaging structure and a processing technology thereof. By optimizing the structural design, processing process and material selection, the heat dissipation performance, electrical performance, production process stability and reliability of the product are improved, the packaging cost is reduced, and significant economic and social benefits are achieved.

[0006] The present invention is achieved through the following technical solutions: A shrink-type top heat dissipation reverse forming packaging structure includes a UeSSOP56L large base island multi-row lead frame unit, and the UeSSOP56L large base island lead frame unit adopts a selective double-sided roughening process; The UeSSOP56L large base island lead frame unit is provided with a plurality of lead frame units arranged in a matrix; the lead frame unit includes a lead frame base island and base island mutual fusion type double rib structures located on the left and right sides of the lead frame base island, the middle area of ​​the lead frame base island is the frame base island, the front side is the chip mounting area, which is used to install the digital power amplifier chip, and the digital power amplifier chip is electrically connected to the corresponding inner pins of the lead frame, and the back side is the packaging structure heat dissipation area, which is used to dissipate heat of the packaged product; A plurality of inner pins are arranged around the lead frame base island, and the plurality of inner pins include an upper left inner pin, an upper right inner pin and other common inner pins. The main body of the long inner pins on the left and right sides of the lead frame base island is arranged in an L-shaped strip shape; the end area of ​​the upper left inner pin and the inner pin connection fusion piece are respectively connected with the two inner pins to form an I-shaped locking structure; A ground wire isolation pin is arranged on the base island mutually fused double connecting rib structure, and the ground wire isolation pin is connected to an adjacent connecting rib of the base island mutually fused double connecting rib through a pin connection fusion sheet inside the lead frame to form an H-type pin structure; the digital power amplifier chip and the lead frame base island are covered with a plastic package.

[0007] Preferably, each lead frame unit is recorded as a group, and flow channel grooves are provided between each group of lead frame units in the horizontal direction, and internal force elimination grooves are provided on the upper and lower sides of each group of lead frame units in the vertical direction; process grooves are provided on the left and right sides of the inner pins of each group of lead frame units.

[0008] Preferably, the head of the inner pin is in the shape of pin fusion, reverse horseshoe, L-shape, goose head side shape, sickle shape, long strip shape, square shovel shape, pin base island rib fusion shape; the inner pin is set to T shape near the encapsulation line.

[0009] Preferably, the lead frame base island fused double connecting ribs are formed by connecting the heads of the fishtail-shaped double connecting ribs on the left and right sides of the lead frame base island; the head of the base island fused double connecting rib structure is connected to the inner pin, and the tail end is connected to the lead frame body through the plastic package.

[0010] Preferably, the back side of the lead frame base island is provided with an extended locking step, a heat sink extended section locking hole and an anti-overflow groove.

[0011] Preferably, a base island electroplated silver layer is provided on the base island of the lead frame, an inner pin electroplated silver layer is provided on the inner pin, and the corresponding base island electroplated silver layer and the inner pin electroplated silver layer are connected by welding wires.

[0012] Preferably, the digital power amplifier chip is installed in the chip mounting area using chip adhesive, and the RDL metal pad on the chip surface is electrically connected to the pin in the lead frame by means of wire diameter and multi-bonding wire.

[0013] Preferably, each group of lead frame units is provided with a gate on the upper right and an exhaust groove on the upper left.

[0014] Preferably, an anti-reverse hole is provided on the top of the UeSSOP56L large base island lead frame unit.

[0015] A processing technology of a shrinkage type top heat dissipation reverse forming packaging structure comprises the following steps: Step 1, thinning and dicing the digital power amplifier chip wafer; Step 2, bonding the digital power amplifier chip to the corresponding position of the base island in the UeSSOP56L large base island lead frame unit; Step 3, electrically connecting the digital power amplifier chip to the corresponding inner pins using welding wires; Step 4, plastic-sealing the welded digital power amplifier chip, lead frame base island, lead frame inner pins, lead frame base island mutual fusion type double connecting ribs, lead frame fishtail connecting ribs and inner pin connection fusion sheet with an external plastic sealing body; Step 5: Tin the lead frame outside the plastic package, cut off the external pin ribs, and make the product shape according to the size of the package body to form the UeSSOP56L large base island package structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a shrinkable top heat dissipation reverse-formed packaging structure with a UeSSOP56L large base island, high power and high heat dissipation and a top heat dissipation reverse-formed automotive-grade audio digital power amplifier circuit packaging structure. A large base island of a lead frame packaging structure is arranged in the central area of ​​a lead frame according to the packaging design process requirements to carry the heat dissipation of a large-size digital power amplifier chip and a packaging structure, and selective double-sided roughening treatment is applied to the entire lead frame unit at the same time. This packaging structure not only ensures the product requirements of large base island, high power and high heat dissipation, and is beneficial to the heat dissipation of high-power products, but also blocks the diffusion of adhesive glue and plastic packaging materials on the front and back sides of the product base island, thereby ensuring and improving the quality and reliability of the product, and also ensuring and improving the encapsulation strength and coplanarity of the entire packaging structure, further improving the product quality and reliability of the packaging structure.

[0017] By setting up a base island mutual fusion type double connecting rib structure on the left and right sides of the lead frame base island, the tail ends of the double connecting ribs on the left and right sides are respectively set in a fishtail shape to connect with the lead frame body, and the inner pin adhesive film is set on the inner pins on the left and right sides of the lead frame; this structure not only ensures the coplanarity of the lead frame base island and the inner pins, so that the deformation of the lead frame in production, delivery and transportation is effectively controlled, but also ensures the process stability of the product at the bonding and wire bonding stations, so that the product quality is guaranteed. At the same time, it solves the problem of lead frame deformation caused by the lead frame packaging delivery process and the core mounting, pressure welding and other links, so that the wire bonding process and plastic sealing process are guaranteed, thereby improving product quality and reliability.

[0018] The present invention abandons the traditional design concept of the lead frame, and sets the base island ground wires on the left and right sides of the lead frame unit as ground wire isolation pins, and connects the base island mutual fusion type double connecting ribs through the lead frame inner pin connection fusion piece to form a small H-shaped pin structure, so that the inner pin can play the dual role of ground wire isolation pin and inner pin; this structure can avoid the desoldering of the welding wire due to the diffusion of the bonding glue on the frame base island, the delamination of the product base island, etc., and ensure the safety of the ground wire welding, thereby ensuring the product quality and reliability of the packaging structure.

[0019] The development of UeSSOP56L packaging technology can rapidly improve the domestic IC packaging technology level and improve the high heat dissipation requirements of products. This project belongs to the field of digital audio amplifier IC packaging chip manufacturing and application technology. The products are widely used in a large number of audio amplifiers such as automotive smart cockpits, E-Call, car speaker entertainment systems, simulated engine sounds, etc., and are also used in conjunction with external DSPs to debug the effects of car speaker systems.

[0020] Furthermore, the T-shaped inner pin end is used to lock the packaging structure during encapsulation, which can improve product quality and reliability; the two inner pins at the upper left end and the upper right end are respectively connected to the two inner pins through the inner pin connecting fusion piece to form an I-shaped locking structure, which improves the locking of the packaging structure during product encapsulation. This method can not only ensure that the plastic package body and the inner pins are firmly combined, but also prevent moisture from penetrating into the carrier, thereby improving product reliability.

[0021] Furthermore, the main body of the long inner pins on the left and right sides of the lead frame are set to be L-shaped strips, which are fixed with a frame adhesive film to ensure the coplanarity balance of the inner pins; on the one hand, the inner pins are tightly fixed by locking the plastic packaging material to reduce the stress caused by thermal expansion that causes the inner pins to move, and prevent the outer pins from pulling the inner pins out of the plastic packaging body when the rib cutting and forming mold is punched and formed, thereby eliminating the damage of the product colloid, greatly improving the encapsulation and reliability of the packaging structure; on the other hand, the bonding strength between the lead frame copper alloy substrate and the plastic packaging material is improved, thereby improving the sealing and waterproof and moisture-proof performance of the UeSSOP56L lead frame packaging structure.

[0022] Furthermore, the ground isolation pins on the left and right sides are connected to the nearest connecting ribs of the double connecting ribs of the base island through the inner pin connecting fusion piece, and the two inner pins at the upper left end and the upper right end are respectively connected to the two inner pins through the inner pin connecting fusion piece to achieve electrical connectivity of the packaging structure; the tail ends of the double connecting ribs on the left and right sides are respectively set to fishtail shape and connected to the lead frame body.

[0023] Furthermore, the anti-overflow groove is used to prevent the plastic packaging material from overflowing and spreading to the heat sink area, ensuring that the appearance of the heat sink meets the quality standards, thereby improving product quality; the extended locking step extends from the base island heat sink to the cross-section locking hole, which is used to lock the glue when encapsulating the packaging structure, thereby improving the encapsulation strength of the entire packaging structure, while ensuring the coplanarity of the packaging structure, further improving the product quality and reliability of the packaging structure.

[0024] Furthermore, on the entire lead frame, only the areas on the inner pin heads, the ground isolation pins that require wire bonding, and the base islands that require chip bonding are treated with electroplating silver, and the remaining areas use AuAgPdNi+ selective double-sided roughening treatment process on bare copper. This ensures the safety of welding the inner pins and ground isolation pins while ensuring the product quality and reliability of the packaging structure.

[0025] Furthermore, by bonding a single digital power amplifier chip to the base island of the lead frame unit, the RDL metal pad on the surface of the chip is electrically connected to the pin inside the lead frame by using thick wire diameter and multiple welding wires, the length of the welding wire is reduced, the resistance of the UeSSOP56L packaging structure is smaller, the on-current is increased, the product heat is reduced, and the product's electrical signal suppression capability is improved, which meets the packaging requirements of products with larger output currents, improves the application performance and use range of the UeSSOP56L packaging structure products, and also reduces the packaging cost of the UeSSOP56L packaging structure products.

[0026] The present invention discloses a shrinkable top heat dissipation reverse forming packaging structure processing technology starting from the product manufacturing method, optimizing the product packaging process flow, optimizing the key site product packaging parameters and manufacturing method, and eliminating the tinning packaging link, thereby completely solving the hidden dangers of tinning causing the packaging structure heat sink to expose copper, colloid end surface tin wire and the like, while improving the product production efficiency, reducing the product packaging cost, and improving and ensuring the product reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the matrix structure of the UeSSOP56L lead frame of the present invention; Figure 2 The UeSSOP56L lead frame unit structure of the present invention is shown in FIG. Figure 1 ; Figure 3 The UeSSOP56L lead frame unit structure of the present invention is shown in FIG. Figure 2 ; Figure 4 The UeSSOP56L lead frame unit structure of the present invention is shown in FIG. Figure 3 ; Figure 5 This is a schematic diagram of the heat sink structure of the UeSSOP56L lead frame unit of the present invention; Figure 6 It is a schematic diagram of the electroplated silver layer of the UeSSOP56L lead frame unit structure of the present invention; Figure 7 This is a schematic diagram of chip bonding of the UeSSOP56L packaging structure of the present invention; Figure 8 This is a schematic diagram of the welding wire of the UeSSOP56L packaging structure of the present invention; Fig. 9 This is a schematic diagram of the glue creeping and glue thickness on the core of the UeSSOP56L packaging structure of the present invention; Fig.10 It is a schematic diagram of the core baking curve of the UeSSOP56L package structure of the present invention; Fig.11This is a process flow chart of the UeSSOP56L packaging structure processing of the present invention; Fig.12 It is a front view of the UeSSOP56L packaging structure of the present invention; Fig.13 This is a rear view of the UeSSOP56L packaging structure of the present invention; Fig.14 It is the right view of the UeSSOP56L packaging structure of the present invention.

[0028] Figure numerals: 1, UeSSOP56L lead frame unit; 2, flushing channel groove; 3, internal force elimination groove; 4, process groove; 5, anti-reverse hole; 6, plastic package; 7, inlet gate; 8, exhaust groove; 9, lead frame inner pin adhesive film; 10, inner pin; 11, ground wire isolation foot; 12, lead frame base island mutual fusion type double connecting rib; 12-1, heat sink base island connecting rib; 13, fishtail-shaped double connecting rib; 14, inner pin connection fusion plate; 15, lead frame base island; 16, extended locking step; 16-1, base island heat sink extended section locking hole; 17, anti-overflow groove; 18, Base island heat sink; 19. Inner pin silver plating layer; 20. Base island silver plating layer; 21. High thermal conductivity chip bonding glue; 22. Digital power amplifier chip; 23. Chip bonding wire; 24. Frame package; 25. Package top pin mark; 26. Package length; 27. Colloid thickness on package; 28. Package thickness; 29. ​​Colloid bevel surface on package; 30. Package width; 31. Package pin span; 32. Chip thickness; 33. High thermal conductivity adhesive thickness; 34. High thermal conductivity adhesive creep height; 35. Five-stage core baking curve; T, lead frame material thickness. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0030] The present invention discloses a shrinkable top heat dissipation reverse forming packaging structure, referring to Figure 1 , including a UeSSOP56L lead frame unit 1, on which a multi-row single-island single-chip packaging structure arranged in a matrix with high density is arranged. Among them, the lead frame includes several lead frame units of one-fill-one structure arranged in a matrix. One-fill-one means that there is a lead frame unit on each side of the horizontal direction of the flushing channel, that is, there is a packaging structure on each side after the product is plastic-sealed; a single base island refers to a single base island that carries a chip in a lead frame unit. Each lead frame unit is a group in the horizontal direction, and a flushing channel 2 is provided between each group of lead frame units, and an internal force elimination groove 3 is provided between each lead frame unit in the vertical direction. Specifically, the central area of ​​the base island of the UeSSOP56L lead frame unit is the chip installation area, and a group of process grooves 4 and a group of internal force elimination grooves 3 are arranged on the left and right sides of the base island, and the base island is connected to the lead frame body through a group of process grooves 4 and a group of internal force elimination grooves 3 in the upper left and lower left, upper right and lower right, respectively.

[0031] The entire lead frame unit is designed with a base island fused double rib structure. The back of the base island is provided with a base island back side extended locking step 16, a base island heat sink extended section locking hole 16-1 and a base island back side anti-overflow groove 17 for blocking the diffusion of plastic packaging material. The entire lead frame is selectively treated with a double-sided roughening process, thereby providing a safety guarantee for product quality and reliability.

[0032] The top of the UeSSOP56L lead frame body is provided with anti-reverse holes 5 at the corresponding positions of each lead frame unit group to prevent lead frame mixing and reverse sealing abnormalities during packaging on the production line, which would cause the packaged products to be scrapped.

[0033] The head of the inner pin 10 in the UeSSOP56L lead frame unit is in the shape of pin mutual fusion (concave or rectangular), reverse horseshoe, L-shape, goose head side shape, sickle shape, long strip, square spade shape or pin base island rib mutual fusion type.

[0034] A total of 56 inner pins 10 are arranged on the four sides of the lead frame base island 15. The ground isolation pins 11 on the left and right sides of the lead frame base island 15 are connected to the base island mutual fusion type double connection ribs 12 through the lead frame inner pin connection fusion sheet 14, and the base island mutual fusion type double connection ribs 12 are connected to the lead frame base island 15, thereby realizing the connection between the ground isolation pins 11 and the lead frame base island 15. The ground isolation pins 11 are used as the base island ground wire, and are connected to the base island mutual fusion type double connection ribs 12 through the lead frame inner pin connection fusion sheet 14, forming a small h-shaped pin structure, so that this inner pin serves as a ground isolation pin and an inner pin. This structure not only avoids the desoldering of the ground wire due to the diffusion of adhesive on the lead frame base island 15, the delamination of the product base island, etc., but also ensures the safety of ground wire welding, thereby improving product quality and reliability.

[0035] The connecting ribs on the left and right sides of the lead frame base island are set to form a double connecting rib structure with the base island fused together, and the tail end is set to be connected to the lead frame body in a fishtail shape, and an inner pin adhesive film is set on the L-shaped long inner pins on the left and right sides; this structure not only ensures the coplanarity of the lead frame base island and the inner pins, and the overall strength of the lead frame, so that the deformation of the lead frame in production, delivery and transportation is effectively controlled, but also ensures the process stability of the product at the bonding and wire welding stations, so that the product quality is guaranteed. The problem of lead frame deformation caused by the lead frame transmission process, core loading, pressure welding and other links is solved, so that the wire welding process and plastic sealing process are guaranteed, thereby improving product quality and reliability.

[0036] like Figure 6 As shown, through the above structural design, a base island electroplated silver layer 20 equivalent to the chip size is set in the chip mounting area at the center of the lead frame base island 15, and an inner pin electroplated silver layer 19 is set at the head of the inner pin 10 and the ground isolation pin 11 of the lead frame. The inner pin electroplated silver layer 19 is process-controlled with an accuracy of ±0.025μm; the other areas of the lead frame base island 15 and the inner pin 10 and the ground isolation pin 11 are bare copper, in order to improve the reliability and quality of the packaging structure product and prevent the diffusion of the adhesive of the lead frame base island 15, which causes product stratification, thereby affecting the heat dissipation, reliability and quality of the product of the entire packaging structure.

[0037] The entire lead frame structure is a bent base island (heat sink) exposed structure. At the same time, the AuAgPdNi+ double-sided roughening process is used for the bare copper on the entire lead frame surface. Through the above special structural design and combined with the ±0.025μm precision control silver plating process, the coplanarity of the lead frame base island 15 is guaranteed, the safety of the isolated ground wire and the inner pin welding wire is guaranteed, and the quality and reliability of the product are guaranteed. At the same time, the lead frame base island 15 is connected to the main body of the UeSSOP56L lead frame unit 1 through the process groove 4, the internal force elimination groove 3, the fishtail-shaped double connecting ribs 13 and the base island mutual fusion type double connecting ribs 12, respectively, to ensure the stability of the entire lead frame structure.

[0038] according to Figure 7 The bonding position of the chip in the die bonding diagram is that a high thermal conductivity chip bonding adhesive 21 is placed in the chip mounting area in the middle of the lead frame base island 15, and the digital power amplifier chip 22 is bonded to the chip mounting area of ​​the lead frame base island 15. Figure 8 The chip bonding method of the packaging structure in the packaging structure bonding diagram connects the RDL metal pad on the surface of the digital power amplifier chip 22 to the strip inner pin electroplated silver layer 19 on the lead frame ground isolation pin 11 through the chip bonding wire 23 to achieve electrical connection of the packaging structure.

[0039] The second surface of the UeSSOP56L lead frame unit 1 , the digital power amplifier chip 22 and the chip bonding wires 23 is covered with a plastic package 6 .

[0040] The RDL metal pad on the surface of the digital power amplifier chip 22 is connected to the electroplated silver layer 19 of the head of the inner pin 10 arranged on the four sides of the lead frame base island 15 and having a pin-interfused shape (concave or rectangular), reverse horseshoe, L-shaped, goose head side shape, sickle-shaped, long strip, square spade-shaped or pin-base island rib-interfused type through the chip bonding wire 23. By bonding wires in the above manner, the electrical connection of the product of the entire packaging structure is realized, and at the same time, the base island electroplated silver layer 20 in the middle of the lead frame base island 15 is firmly bonded to the back of the digital power amplifier chip 22 through the high thermal conductivity chip bonding glue 21, realizing and ensuring the dissipation of the heat of the entire packaging structure product when it is working, thereby ensuring the quality and reliability of the packaging structure. By bonding a single digital power amplifier chip to the base island of the lead frame unit, the RDL metal pad on the surface of the chip is electrically connected to the pins in the lead frame by using thick wire diameter and multiple wire bonding (130 50μm AuPdCu), thereby reducing the length of the wires. This reduces the resistance of the UeSSOP56L package structure, increases the on-current, reduces the heat generation of the package structure, and improves the electrical signal suppression capability. This meets the packaging requirements of the package structure outputting a large current and dissipating a large amount of heat generated by the chip during operation, thereby improving the application performance, work efficiency and use range of the UeSSOP56L package structure products, and also reduces the packaging cost of the UeSSOP56L package structure.

[0041] The present invention discloses a shrinkable top heat dissipation reverse-formed packaging structure with a UeSSOP56L large base island, high power and high heat dissipation and a top heat dissipation reverse-formed automotive-grade audio digital power amplifier circuit packaging structure. A large base island of a lead frame packaging structure is arranged according to the packaging design process requirements to carry a large-size digital power amplifier chip. An electroplated silver layer and a chip bonding glue anti-diffusion groove equivalent to the chip size are arranged on the front side of the base island. A double U-shaped or V-shaped closed anti-overflow groove 17, a base island extension locking step with a thickness of T / 2 of the lead frame material thickness, and a base island heat sink extension section locking hole are arranged on the back side of the base island. At the same time, selective double-sided roughening treatment is adopted for the entire lead frame unit. This packaging structure not only guarantees the product demand for large base island, high power and top heat dissipation, which is beneficial to the heat dissipation of high power products, but also blocks the diffusion of adhesive glue on the front side of the product base island and plastic sealing material on the back side, thereby ensuring and improving the quality and reliability of the product. At the same time, it also guarantees and improves the encapsulation strength and coplanarity of the entire packaging structure, further improving the product quality and reliability of the packaging structure, and solves the problem that audio power amplifier products cannot meet the product demand for high power, high heat dissipation and reliability due to product current linear overcurrent, product heat dissipation, product output power, product anti-interference, harsh environment adaptability, AM / FM reception sensitivity, impedance, saturation voltage drop, efficiency, product reliability and other problems. Innovation and optimization are carried out in product frame structure design, frame process processing, inner pin and base island silver plating method, plastic sealing body pores, production process and flow, thereby improving product production efficiency, reducing product packaging costs, and improving product quality and reliability.

[0042] The development of UeSSOP56L reverse molding package products can meet the needs of the development of modern industry, communication, automobile and other fields, so that the products have the characteristics of low distortion, low noise, large dynamic range, strong anti-interference and ability to adapt to harsh environments, high AM / FM reception sensitivity, high product output power (instantaneous 4*100W output, continuous 4*50W output), low impedance, good current linearity, small saturation voltage drop, high efficiency, and overheating short circuit protection. The audio digital amplifier can achieve high power, high heat dissipation and low thermal resistance required by the product. Compared with the existing T / SSOP48L single base island lead frame, it has the advantages of high density arrangement, high copper material utilization, improves the production efficiency of existing products, saves a lot of manpower and material resources, and the UeSSOP56L product has a large colloid size and a high material utilization rate of the entire product. The product application can not only meet the functions of T / SSOP48L single base island products, but also replace the existing T / SSOP48L product packaging. At the same time, the entire package structure is top-heated, which solves the space limitation of the product PCB board. According to the requirements of the product package structure, a special thermally enhanced PCB board is customized on it, thereby providing heat dissipation for the entire package structure and ensuring the quality and reliability of the product. See Table 1 for a comparison of the lead frame related dimensions.

[0043] Table 1 Comparison of dimensions of the frame of the present invention and existing frames

[0044] Example A UeSSOP56L lead frame unit 1 is used for electrically connecting a digital power amplifier chip to external pins; the UeSSOP56L large base island lead frame unit includes a lead frame base island 15 for carrying the chip on the front side and a lead frame base island heat sink 18 for dissipating heat from the packaging structure on the back side.

[0045] Among them, the UeSSOP56L lead frame unit 1 includes 4 rows and 10 columns, a total of 40 lead frame units. Specifically, the frame size of the UeSSOP56L lead frame unit 1 is length × width × thickness: 251.000 × 67.400 × 0.152 mm, the large unit pitch: 50.199 mm, the small unit pitch: 25.100 mm, the cumulative unit pitch: 225.900 mm, the center distance between the two plastic packages: 25.100 mm, the distance from the positioning hole to the lead frame corner cut, the starting end is 12.550 mm, and the end end is 12.550 mm.

[0046] The lead frame base island 15 is provided with a base island back extension locking step 16 with a thickness of T / 2 of the lead frame material thickness, a base island heat sink extension cross-section locking hole 16-1, and a base island back anti-overflow groove 17 to prevent the diffusion of the plastic packaging material, which in turn constitute a complete UeSSOP56L lead frame base island structure unit. Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, a flushing channel groove 2 is provided between each group of lead frame units, and a process groove 4 and an internal force elimination groove 3 with the same structure are provided on both sides of the upper and lower pins of each group of lead frame units.

[0047] The UeSSOP56L lead frame has a total of 56 inner pins on the upper, lower, left and right sides of the large base island. Among them, the inner pins 10 of the lead frame and the heads of the ground isolation pins 11 are provided with inner pin electroplating silver layers 19, and the chip bonding area of ​​the lead frame base island 15 is provided with a base island electroplating silver layer 20.

[0048] The ends of the 56 inner pins on the four sides of the UeSSOP56L lead frame unit (the distance from the encapsulation line) are all set to an inverted T shape, and the two inner pin end areas at the upper left and upper right ends are respectively connected to the two inner pins 10 through the inner pin connection fusion piece 14 to form an I-shaped locking structure; the ground wire isolation pin 11 is connected to an adjacent connecting rib of the base island mutual fusion type double connecting rib 12 through the lead frame inner pin connection fusion piece 14 to form an H-shaped pin structure; base island mutual fusion type double connecting ribs 12 are set on the left and right sides of the lead frame base island, and the tail ends of the fishtail-shaped double connecting ribs 13 on the left and right sides are connected to the lead frame body through the plastic package 6, and the heads of the fishtail-shaped double connecting ribs 13 on the left and right sides are connected to the base island mutual fusion type double connecting ribs 12 to form an integral lead frame base island connecting rib structure; inner pin adhesive films 9 are set on the inner pins on the left and right sides of the lead frame to ensure the coplanarity of the lead frame base island and the inner pins.

[0049] like Fig. 9 , Fig.10 As shown, a UeSSOP56L large island high power top heat dissipation reverse forming package structure lead frame core packaging process, a digital power amplifier chip 22 with a chip thickness 32 of 360μm±10μm, according to Fig. 9 The method shown in the figure is placed on the high thermal conductive adhesive thickness 33 with a wet adhesive thickness of 40μm±5μm, ensuring that the high thermal conductive adhesive creeping height 34 on the four sides of the digital power amplifier chip 22 reaches 50% of the chip thickness 32. After the chip is bonded, follow the Fig.10 The schematic requires that the adhesive curing is completed by a five-stage core baking curve 35 and a vacuum high-temperature oxygen-free independent exhaust facility baking oven with a five-stage core baking curve 35, so that the digital power amplifier chip 22 is firmly bonded to the base island electroplated silver layer 20 on the lead frame base island 15. This is because the package has the characteristics of large base island, high power and high heat dissipation. The chip is a four-channel high heat dissipation power consumption chip, and it must be matched with a high thermal conductivity adhesive to dissipate the heat generated during product operation through the top heat sink. In this way, the packaged product after core loading can eliminate the impact of packaging stress on the packaged product after core loading through a moderate rising and falling baking process, thereby improving product reliability and quality, and ensuring that the heat generated by the digital power amplifier chip 22 during operation passes through the large-area heat dissipation pad base island heat sink 18 at the bottom of the UeSSOP56L packaging structure, thereby effectively transferring the working heat of the digital power amplifier chip 22 to form a good thermal conductivity performance of the packaging structure.

[0050] like Fig.11 As shown, the UeSSOP56L large-island high-power top-heat dissipation reverse-formed packaging structure lead frame single-chip packaging processing technology of the present invention starts with wafer incoming inspection, goes through multiple manufacturing stations such as dicing and thinning, die attach and wafer bonding, and finally completes product packaging and shipment. The stations to be passed in the middle and the corresponding process flow requirements form a complete production process flow. like Figures 12-14 As shown, the UeSSOP56L large island high-power top heat dissipation reverse forming package structure lead frame chip package product of the present invention is formed. The heat sink surface of the package structure is located on the front of the plastic package body. The product package body size is 18.40mm x 7.50mm x 2.30mm in length x width x thickness, and the e Ptich is 0.635 mm, the pin span is 10.30mm, and the various parts thereon are: four package ejector pin marks 25 are designed on the front and back of the frame package 24, and the small spherical surface 25 on the front is the Pin1 positioning mark, and a large circular plane is designed in the diagonal direction (used to distinguish it from the Pin1 positioning mark), and a group of large circular planes 25 are designed on the left and right sides of the center line of the plastic package on the back, and the colloid bevel surface 29 on the package improves the demoulding property of the package plastic package mold, thereby ensuring the reliability and quality of the plastic package product; package width 30 (size is 7.50mm), package pin span 31 (size is 10.30mm), package length 26 (size is 18.40mm), package thickness 28 (size is 2.30mm), package upper colloid thickness 27 (size is 0.88mm), through the above data, the key external dimensions of the entire plastic package of the UeSSOP56L package are completed.

[0051] The UeSSOP56L large island high-power top heat dissipation reverse forming package structure lead frame chip package of the present invention has the following processing technology: The first step is to conduct corresponding wafer inspection on the incoming wafers according to the wafer inspection standards and requirements. After completion, the qualified customer wafers will be input to the thinning and dicing station of the packaging department; the thinning and dicing station uses a fully automatic placement machine to automatically place the digital power amplifier chip 22 wafer on the 8-inch or 12-inch collapse film ring; the front of the wafer is pasted with HT-260PG film (UV type), and the 400 mJ / cm² parameter is used to control the debonding to solve the risk of water ingress and residual adhesive contamination of the wafer during the thinning process. At the same time, according to the packaging requirements of the UeSSOP56L product, the chip thickness 32 is controlled within the range of 360μm±10μm. The digital power amplifier chip 22 wafer is automatically thinned from the incoming material thickness of 725μm±20μm according to the thickness control requirement of 360μm±10μm using a fully automatic thinning machine. Then, the fully automatic placement & film stripping machine is used to automatically place & strip the thinned digital power amplifier chip 22 wafers in turn. Place & strip After completion, they are placed in an oven at 50℃±5℃ and baked for 5mins to 10mins; after baking, the digital power amplifier chip 22 wafer is cut into individual digital power amplifier chips 22 using a fully automatic dicing machine; then a high-pressure air gun is used to blow away the waste residue and water stains on the cut digital power amplifier chips 22, and then two-light % inspection is carried out in turn. During the inspection, the digital power amplifier chips 22 with product quality defects will be marked accordingly so that the back-end site can accurately identify them during product packaging. After completion, the qualified digital power amplifier chips 22 will be transported to the chip loading site.

[0052] In the second step, the core loading station uses a high-precision fully automatic core loading machine to automatically absorb a UeSSOP56L large base island high-power top heat dissipation reverse forming packaging structure lead frame of the present invention and place it on the core loading machine transmission rail. The lead frame is automatically transmitted to the center of the core loading machine workbench and automatically clamped by the automatic transmission system of the core loading machine. For the UeSSOP56L large base island high-power top heat dissipation reverse forming packaging structure lead frame package, the glue dispensing robot of the core loading machine is located in the chip mounting area on the base island of the UeSSOP56L large base island high-power top heat dissipation reverse forming packaging structure lead frame unit 1 according to Figure 7 The requirements for the sticking position are as follows: "The appropriate amount of high thermal conductivity chip adhesive 21 is drawn in the chip mounting area in a "shaped manner. The thickness 33 of the high thermal conductivity adhesive is controlled within the range of 40μm±5μm for wet adhesive and 35μm±5μm for dry adhesive. The height 34 of the high thermal conductivity adhesive is controlled at 50% of the chip thickness 32. A high-precision fully automatic chip bonding machine is used, and a rectangular step-free nozzle and P-150MIC*4 ejector are used. According to the chip bonding program set before chip bonding and combined with the MAP chip picking diagram, according to Figure 7The bonding process requires that one chip from the digital power amplifier chip 22 wafer is sequentially bonded and placed on the adhesive 21, and the required number of bonding products is completed in this order. Then, a five-stage core-on baking curve 35 and a vacuum high-temperature oxygen-free independent exhaust facility baking oven are used to perform a core-on bonding one-time curing process. The adhesive is cured by baking in a high-temperature oven to prevent the debonding layer, so that the chip and the lead frame base island are firmly bonded. After baking, the core-on bonding product is transported to the pressure welding station for product wire bonding.

[0053] The third step is to perform plasma cleaning on the UeSSOP56L large island high power top heat dissipation reverse forming package structure lead frame package products before pressing the wires to clean the pollutants on the lead frame and digital amplifier chip to improve the quality and reliability of the product during wire bonding. Then, use a vacuum anti-oxidation pressure welding fixture and a fully automatic ultrasonic wire bonding machine according to the UeSSOP56L lead frame package wire bonding diagram. Figure 8 And related welding wire requirements are to bond the first surface pad of the digital power amplifier chip to the pin 10 in the lead frame and the electroplated silver layer 19 on the ground isolation pin 11 with multiple 50μm AuPdCu chip welding wires 23. In this way, the required number of product welding wires of UeSSOP56L are completed. After the product welding wires are completed, they are inspected by three-light% inspection. Products with quality defects are marked next to the lead frame for easy identification by the back-end site, and then sent to the plastic packaging site for product packaging.

[0054] The fourth step is to perform plasma cleaning on the product before plastic encapsulation to eliminate pollutants, oxides and other substances on the lead frame unit 1, the digital amplifier chip 22 and the chip bonding wire 23, so as to improve the quality and reliability of the encapsulated product. Then, a fully automatic vacuum encapsulation machine is used to select a high-reliability plastic encapsulation material with low stress and good fluidity to complete the encapsulation of the UeSSOP56L product. After that, the encapsulated UeSSOP56L product is blown with ion wind for 12 seconds for natural cooling to further release the product stress and reduce the product warpage. Then, the encapsulated UeSSOP56L product is sent to a high-temperature oven for post-curing. The oven temperature is set at 180℃±10℃, and the baking time is controlled at 10h±0.5h. After the UeSSOP56L product is cured and baked, it is sent to the reflow oven for a reflow process. The UeSSOP56L products are screened, and the UeSSOP56L products with quality abnormalities are screened out and marked on the colloid surface of the product so that the packaging department can remove them when separating the UeSSOP56L lead frame sealing structure products. According to this production method, the quality and reliability of the product are guaranteed. After that, the product is sent to the center rib cutting station for product center rib cutting processing.

[0055] The fifth step is to use the fully automatic rib cutting equipment at the rib cutting station and the rib cutting mold to synchronously punch from the edges of the plastic package on both sides to the gap between the frame frame and the injection port and the exhaust groove to form a punched end face, thereby punching the UeSSOP56L package structure plastic package from the lead frame unit, and then use the UeSSOP56L rib cutting mold to perform the product rib cutting process. After completion, the product is sent to the de-overflow station for product de-overflow processing.

[0056] In the sixth step, the UeSSOP56L lead frame package product completed by the rib cutting station is treated with high-pressure water to remove overflow, and then undergoes a tinning and baking process. After completion, the product is sent to the printing station for product printing. In the seventh step, the printing station uses a fully automatic front and back laser marking machine to print the UeSSOP56L lead frame packaging structure product that has been tinned and baked according to the corresponding printing specifications and customer product requirements. The product traceability code is printed on the front (plastic sealing surface) and the product seal is printed on the back (heat sink surface). After completion, the product is sent to the forming and separation station.

[0057] The eighth step is to use the fully self-forming separation equipment at the forming and separation station to perform process processing according to the following steps. The first step is to pre-form the pins of the UeSSOP56L lead frame package product. The second step is to form the pins of the product. The third step is to cut off the fifty-six pins of the UeSSOP56L lead frame package product. The fourth step is to cut off the pins connected to the process groove 4 and the internal force elimination groove 3 of the UeSSOP56L lead frame package product. In this way, the UeSSOP56L lead frame package product is separated to complete an independent UeSSOP56L large base island high-power top heat dissipation reverse forming package structure package, and the shape structure is as shown in the front view of the package. Fig.12 , rear view of package Fig.13 、Package right view Fig.14 , and then bake before packaging to obtain the finished package, and finally package and ship, completing the packaging of the entire UeSSOP56L large-island high-power top-heat-dissipating reverse-formed package structure product. Compared with the existing processing technology of T / SSOP48L lead frame packaging structure, the production method of the present invention adds two-light inspection and inspection process requirements at the de-scribing site, ensuring the quality and reliability of the de-scribing site products.

[0058] The core loading site uses an adhesive with high reliability, high thermal conductivity (75 W / mK), and strong Ag surface bonding strength. A rectangular step-free core loading nozzle and four ejector pins are used for chip bonding. The thickness of the dry adhesive is controlled within the range of 35μm±5μm, and the adhesive creeping height is controlled within 50% of the chip thickness. A five-stage core loading baking curve and a vacuum high-temperature oxygen-free independent exhaust anti-separation layer baking oven are used for adhesive curing, ensuring a firm bond between the chip and the lead frame base island, thereby fully releasing the stress during the baking of the large chip, ensuring that no voids are generated under the chip, and ensuring the product quality and reliability after core loading and bonding.

[0059] Plasma cleaning is used before pressure welding, vacuum anti-oxidation fixtures are used during pressure welding, and three-light % inspection is performed after the pressure welding wire is completed. This protects the oxidation protection of the lead frame of the thickened wire products at the pressure welding station and ensures the quality and reliability after the wire welding.

[0060] Before plastic encapsulation, the plasma cleaning process is used to treat the product after wire bonding, which not only eliminates pollutants in the lead frame and digital power amplifier chip, lead frame base island oxidation and other factors that affect product quality and reliability, but also provides a strong guarantee for the quality and reliability of the product after plastic encapsulation. At the same time, a reflow soldering process is added after the product is post-cured, and the tinning adopts the hot boiling softening process treatment requirements, so that the product quality and reliability are fully guaranteed, which is more beneficial to the product quality and reliability.

[0061] The rib cutting station first performs the gate punching action before cutting the center rib, then cuts the center rib, then forms the lead, and finally cuts the lead. This series of process steps not only effectively solves the abnormal tin wire on the end surface of the package structure lead frame package, but also meets the process requirements of the rib cutting station products, and meets the process requirements of the special structural design of the package structure lead frame base island connecting rib during product rib cutting and forming, and also fully guarantees the product quality and reliability of the rib cutting station.

[0062] The printing station uses a fully automatic front and back laser marking machine to simultaneously print the product traceability code on the front (plastic sealing surface) and the product seal on the back (heat sink surface). This not only solves the problem of "x" product identification and statistics during the entire product packaging production process, but also prevents scratches and contamination of the product during the product packaging process. The whole process reduces the participation of personnel, improves product production efficiency, and also ensures product quality.

[0063] After forming, the UeSSOP56L package has a top heat dissipation structure, which solves the space limitation of the product PCB board surface with the base island heat sink facing downward in the traditional design. At the same time, according to the requirements of the product packaging structure, a special thermally enhanced PCB board can be customized on the base island heat sink. Through the PCB heat dissipation pad and heat dissipation holes, the excess power consumption can be diffused to the copper ground plate to absorb excess heat, thereby greatly improving the heat dissipation capacity of the chip and ensuring the quality and reliability of the entire packaging structure.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A shrinkable top heat dissipation reverse forming packaging structure, characterized in that: It includes a UeSSOP56L large base island multi-row lead frame unit, the UeSSOP56L large base island lead frame unit adopts a selective double-sided roughening treatment; the UeSSOP56L large base island lead frame unit is provided with a plurality of lead frame units arranged in a matrix; The lead frame unit comprises a lead frame base island (15) and base island mutual fusion type double rib structures located on the left and right sides of the lead frame base island (15); the front side of the middle area of ​​the lead frame base island (15) is a chip mounting area for mounting a digital power amplifier chip (22); the digital power amplifier chip (22) is electrically connected to the corresponding inner pins (10) of the lead frame; and the back side is a packaging structure heat dissipation area for heat dissipation of the packaged product; A plurality of inner pins (10) are arranged around the lead frame base island (15), the plurality of inner pins (10) comprising an upper left inner pin, an upper right inner pin and other common inner pins, the long inner pin main body parts on the left and right sides of the lead frame base island (15) are arranged in an L-shaped strip shape; the upper left inner pin terminal area and the inner pin connection fusion piece are respectively connected to the two inner pins to form an I-shaped locking structure; A ground wire isolation pin (11) is provided on the base island mutually fused double connecting rib structure, and the ground wire isolation pin (11) is connected to an adjacent connecting rib of the base island mutually fused double connecting rib (12) through a lead frame inner pin connection fusion sheet (14), thereby forming an H-shaped pin structure; the digital power amplifier chip (22) and the lead frame base island (15) are externally coated with a plastic package body (6).

2. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: Each lead frame unit is recorded as a group. In the horizontal direction, a flushing channel groove (2) is provided between each group of lead frame units. In the vertical direction, internal force elimination grooves (3) are provided on the upper and lower sides of each group of lead frame units. Process grooves (4) are provided on the left and right sides of the inner pins (10) of each group of lead frame units.

3. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: The head of the inner pin (10) is in the shape of a pin fusion, a reverse horseshoe, an L shape, a goose head side shape, a sickle shape, a long strip shape, a square spade shape, or a pin base island rib fusion shape; the inner pin (10) is arranged in a T shape near the encapsulation line.

4. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: The lead frame base island fused double connecting ribs (12) are formed by connecting the heads of the fishtail-shaped double connecting ribs (13) on the left and right sides of the lead frame base island (15); the heads of the fishtail-shaped double connecting ribs (13) are connected to the inner pins (10), and the tail ends are connected to the lead frame body through the plastic package (6).

5. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: The back side of the lead frame base island (15) is provided with an extended locking step (16), a heat sink extended section locking hole (16-1) and an anti-overflow groove (17).

6. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: A base island electroplated silver layer (20) is provided on the lead frame base island (15), and an inner pin electroplated silver layer (19) is provided on the inner pin (10); the corresponding base island electroplated silver layer (20) and the inner pin electroplated silver layer (19) are connected by welding wires.

7. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: The digital power amplifier chip (22) is mounted on the chip mounting area using chip adhesive, and the RDL metal pad on the surface of the chip is electrically connected to the pin (10) in the lead frame by means of thick wire diameter and multiple welding wires.

8. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: A gate (7) is provided on the upper right of each group of lead frame units, and an exhaust groove (8) is provided on the upper left.

9. The shrinkable top heat dissipation reverse-shaped packaging structure according to claim 1, characterized in that: An anti-reverse hole (5) is provided on the top of the UeSSOP56L large base island lead frame unit.

10. A processing technology for a shrinkable top heat dissipation reverse forming packaging structure as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1, thinning and dicing the digital power amplifier chip (22) wafer; Step 2, bonding the digital power amplifier chip (22) to the corresponding position of the base island in the UeSSOP56L large base island lead frame unit; Step 3, electrically connecting the digital power amplifier chip (22) and the corresponding inner pin (10) using a welding wire; Step 4, plastic-sealing the welded digital power amplifier chip (22), the lead frame base island (15), the lead frame inner pin (10), the lead frame base island (15) mutually fused double connecting ribs (12), the lead frame fishtail connecting ribs (13), and the inner pin (10) with the external plastic-sealing body (6) of the fusion sheet; Step 5, tinning the outer lead frame of the plastic package (6), cutting off the outer lead connecting ribs, and manufacturing the product shape according to the size of the package body to form a UeSSOP56L large base island package structure.

Images