A shrinkage top heat dissipation type reverse forming packaging structure and a processing technology thereof

Abstract

The present application relates to the field of digital power amplifier circuit IC packaging applications, specifically to a shrinkage top heat dissipation type reverse forming packaging structure and its processing technology, the packaging structure is provided with a lead frame packaging structure large base island, which carries a large size digital power amplifier chip, a base island mutual fusion type double rib structure is arranged on the left and right sides of the lead frame base island, the tail ends of the double ribs on the left and right sides are respectively provided with a fishtail shape in communication with the lead frame main body, the RDL metal pads on the surface of the chip are electrically connected with the inner pins of the lead frame through the way of thick wire diameter and multiple soldering wires, this packaging structure not only ensures the product demand of large base island large power top heat dissipation type, is beneficial to the heat dissipation of large power products, but also blocks the diffusion of product base island front adhesive glue and back plastic sealing material, thereby ensuring and improving the product quality and reliability, and also ensuring and improving the package strength and coplanarity of the whole packaging structure, further improving the product quality and reliability of the packaging structure.

Description

Technical Field

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

[0002] Traditional amplifiers primarily amplify power, and while their functionality generally varies, their key differences lie in performance, distortion, signal-to-noise ratio, and controllability. Due to the size of the entire amplifier circuit, its output power is limited, resulting in a narrow dynamic range, with a single channel outputting only approximately 10-40W. This results in a single function and an unadjustable sound field. Traditional amplifiers dissipate a significant amount of power as heat, leading to issues such as heat generation, noise, poor sound quality, and low efficiency throughout the circuit. At low power levels, the switching of the positive and negative channels often results in crossover distortion.

[0003] New energy vehicles are increasingly prioritizing the intelligent cockpit audio experience. High-power amplifiers, Dolby Atmos, and Atmos are gradually entering the automotive market. Ultra-multi-channel, ultra-powerful amplifier designs are revolutionizing traditional car audio design. The rapid development of digital amplifier technology, in particular, has enabled high-power, multi-channel, high-performance amplifier systems, making mobile theaters, karaoke bars, and HIFI audio systems possible. With breakthroughs in digital amplifier technology, digital amplifiers have become mainstream in new energy vehicles. Unlike traditional amplifiers, digital amplifiers operate on switching signals, offering high switching frequencies, high efficiency, high performance, high power, high dynamic range, ultra-high linearity, and ultra-low distortion. The automotive industry currently represents a massive market, making car audio a key competitive area for many audio manufacturers. The booming development of new energy vehicles will further expand the market, creating opportunities for emerging car audio companies. Furthermore, with China's continued rapid economic growth, the demand for automobiles will continue to grow, creating new opportunities for car audio development. Digital amplifiers are expected to be even more widely used in the automotive audio field in the future.

[0004] The UeSSOP56L (Shrink Small Outline Package (Up Exposed Thermal Paddle)) shrinkable, top-cooled, reverse-molded IC package technology is a new SMT (surface mount technology) technology with an exposed (upward) heat sink. The UeSSOP56L package is not available on the market, and the similar T / SSOP48L package lacks a heat sink. This product's heat dissipation falls far short of customer requirements. The product's anti-interference and harsh environment adaptability, AM / FM reception sensitivity, dynamic range, output power, impedance, current linearity, saturation voltage drop, efficiency, and overtemperature and short-circuit protection fall short of automotive-grade requirements. Therefore, technological innovation is needed to develop new products and corresponding packaging processes to resolve existing issues and improve product quality and application scope. Summary of the Invention

[0005] In response to the problem in the existing technology that the heat dissipation performance, anti-interference and adaptability to harsh environments, and electrical performance of T / SSOP48L packaging products without heat sinks cannot meet automotive-grade requirements, the present invention provides a shrinkable top-heat dissipation reverse-formed packaging structure and its processing technology. By optimizing the structural design, processing process and material selection, the product's heat dissipation performance, electrical performance, production process stability and reliability are improved, the packaging cost is reduced, and it has significant economic and social benefits.

[0006] The present invention is achieved through the following technical solutions:

[0007] A shrinkable top-heat-dissipating reverse-molded package structure includes a UeSSOP56L large-base-island multi-row lead frame unit, wherein the UeSSOP56L large-base-island lead frame unit adopts a selective double-sided roughening process;

[0008] The UeSSOP56L large base island lead frame unit is equipped with several 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 central area of ​​the lead frame base island is the frame base island. The front side is the chip mounting area for installing the digital power amplifier chip. The digital power amplifier chip is electrically connected to the corresponding inner pins of the lead frame. The back side is the packaging structure heat dissipation area for dissipating heat from the packaged product.

[0009] Several inner pins are arranged around the lead frame base island, including an upper left inner pin, an upper right inner pin, and other ordinary inner pins. The main body of the long inner pins on the left and right sides of the lead frame base island is set as an L-shaped strip; the end area of ​​the upper left inner pin and the inner pin connection piece are connected to the two inner pins respectively through the inner pin connection piece, forming an I-shaped locking structure;

[0010] A ground isolation pin is provided on the base island mutually integrated double connecting rib structure, and the ground isolation pin is connected to an adjacent connecting rib of the base island mutually integrated double connecting rib through a pin connection piece inside the lead frame to form an H-shaped pin structure; the digital power amplifier chip and the lead frame base island are covered with a plastic package.

[0011] 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.

[0012] Preferably, the heads of the inner pins are in the shape of pin mutual fusion, reverse horseshoe, L-shape, goose head side shape, sickle shape, long strip shape, square shovel shape, pin base island rib mutual fusion shape; the inner pins are all set to T-shape near the encapsulation line.

[0013] Preferably, the lead frame base island mutually 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 mutually 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.

[0014] 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.

[0015] Preferably, a base island electroplated silver layer is provided on the lead frame base island, 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.

[0016] 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 adding multiple wires.

[0017] Preferably, a gate is provided on the upper right side of each group of lead frame units, and an exhaust groove is provided on the upper left side.

[0018] Preferably, an anti-reflection hole is provided on the top of the UeSSOP56L large base island lead frame unit.

[0019] A processing technology for a shrinkable top-heat-dissipating reverse-molded packaging structure includes the following steps:

[0020] Step 1: Thinning and dicing the digital power amplifier chip wafer;

[0021] Step 2: Bond the digital power amplifier chip to the corresponding position of the base island in the UeSSOP56L large base island lead frame unit;

[0022] Step 3: Electrically connect the digital power amplifier chip to the corresponding internal pins using bonding wires;

[0023] Step 4: Plastic encapsulate 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 encapsulation body;

[0024] Step 5: Tin the lead frame outside the plastic package, remove the external pin ribs, and make the product shape according to the package size to form the UeSSOP56L large base island package structure.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a shrinkable top-heat-dissipating reverse-formed packaging structure with a UeSSOP56L large-base-island, high-power, high-heat dissipation, and top-heat-dissipating reverse-formed automotive-grade audio digital power amplifier circuit packaging structure. A large base island of the lead frame packaging structure is provided in the central area of ​​the lead frame according to the packaging design process requirements to carry the heat dissipation of a large-size digital power amplifier chip and the packaging structure. At the same time, a selective double-sided roughening treatment is applied to the entire lead frame unit. This packaging structure not only meets the product requirements of the large base island for 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 material on the front and back sides of the product base island, thereby ensuring and improving the quality and reliability of the product, but also ensures and improves the encapsulation strength and coplanarity of the entire packaging structure, further improving the product quality and reliability of the packaging structure.

[0027] By installing mutually integrated dual ribs on the left and right sides of the leadframe island, with the tail ends of the dual ribs connected to the leadframe body in a fishtail shape, and applying inner pin adhesive film to the inner pins on both sides of the leadframe, this structure not only ensures the coplanarity of the leadframe island and inner pins, effectively controlling deformation of the leadframe during production, transportation, and other aspects, but also ensures process stability at the die bonding and wire bonding stations, thus guaranteeing product quality. At the same time, it solves the problem of leadframe deformation caused by the leadframe package transfer process, core loading, and pressure welding, ensuring the wire bonding and plastic encapsulation processes, thereby improving product quality and reliability.

[0028] 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. The lead frame inner pin connection fusion piece is connected to the base island mutual fusion type double rib to form a small H-shaped pin structure, so that the inner pin can serve as both a ground wire isolation pin and an inner pin. This structure avoids the desoldering of the ground wire due to the diffusion of adhesive on the frame base island, the delamination of the product base island, etc., and ensures the safety of the ground wire welding, thereby ensuring the product quality and reliability of the packaging structure.

[0029] The development of UeSSOP56L packaging technology can rapidly advance domestic IC packaging technology and address the high heat dissipation requirements of products. This project addresses the manufacturing and application of digital audio amplifier IC packaging chips. These products are widely used in a wide range of audio amplifier applications, including automotive smart cockpits, E-Call, car audio entertainment systems, and simulated engine sounds. They also integrate with external DSPs for tuning car audio systems.

[0030] 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, forming 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.

[0031] 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 long strips, which are fixed with 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, reducing the stress caused by thermal expansion that causes the inner pins to move, and preventing 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.

[0032] 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 connection fusion plate, and the two inner pins at the upper left and upper right ends are respectively connected to the two inner pins through the inner pin connection fusion plate, thereby realizing the 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.

[0033] 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 standard requirements, 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.

[0034] 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 electroplated with silver. The remaining areas use a AuAgPdNi+ selective double-sided roughening process on bare copper. This ensures the safety of wire bonding of the inner pins and ground isolation pins while guaranteeing the product quality and reliability of the packaging structure.

[0035] Furthermore, by bonding a single digital power amplifier chip to the base island of the lead frame unit, and electrically connecting the RDL metal pad on the chip surface to the pins inside the lead frame by using thick wire diameter and multiple welding wires, the length of the welding wires can be reduced, making the resistance of the UeSSOP56L packaging structure smaller, the on-state current increased, and the product heat generation reduced, the product's electrical signal suppression capability improved, meeting the packaging requirements of products with larger output currents, improving the application performance and usage range of the UeSSOP56L packaging structure products, and also reducing the packaging cost of the UeSSOP56L packaging structure products.

[0036] The present invention provides a shrinkage-type top-heat-dissipating reverse-formed packaging structure processing technology that starts with the product manufacturing method, optimizes the product packaging process flow, optimizes the packaging parameters and manufacturing methods of key site products, and eliminates the tinning packaging link, thereby completely solving the hidden dangers of exposed copper on the heat sink of the packaging structure and tin wire on the end face of the colloid caused by tinning. At the same time, it improves product production efficiency, reduces product packaging costs, and improves and guarantees product reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the matrix structure of the UeSSOP56L lead frame of the present invention;

[0038] Figure 2 Schematic diagram of the UeSSOP56L lead frame unit structure of the present invention Figure 1 ;

[0039] Figure 3 Schematic diagram of the UeSSOP56L lead frame unit structure of the present invention Figure 2 ;

[0040] Figure 4 Schematic diagram of the UeSSOP56L lead frame unit structure of the present invention Figure 3 ;

[0041] Figure 5 This is a schematic diagram of the heat sink structure of the UeSSOP56L lead frame unit of the present invention;

[0042] Figure 6 Schematic diagram of the silver plating layer of the UeSSOP56L lead frame unit structure of the present invention;

[0043] Figure 7 This is a schematic diagram of the die bonding of the UeSSOP56L package structure of the present invention;

[0044] Figure 8 This is a schematic diagram of the wire bonding of the UeSSOP56L package structure of the present invention;

[0045] Figure 9 Schematic diagram of glue creepage and glue thickness on the core of the UeSSOP56L package structure of the present invention;

[0046] Figure 10 Schematic diagram of the core baking curve of the UeSSOP56L package structure of the present invention;

[0047] Figure 11 This is a process flow chart of the UeSSOP56L package structure processing of the present invention;

[0048] Figure 12 This is a front view of the UeSSOP56L package structure of the present invention;

[0049] Figure 13 This is a rear view of the UeSSOP56L package structure of the present invention;

[0050] Figure 14 This is the right side view of the UeSSOP56L package structure of the present invention.

[0051] 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 pin; 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 piece; 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 adhesive; 22. Digital power amplifier chip; 23. Chip bonding wire; 24. Frame package; 25. Package ejector mark; 26. Package length; 27. Glue thickness on package; 28. Package thickness; 29. ​​Glue 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

[0052] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0053] The present invention discloses a shrinkage type top heat dissipation type 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 provided.

[0054] Among them, the lead frame includes several lead frame units of a one-fill-one structure arranged in a matrix. One-fill-one means that there is a lead frame unit on each side in 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. 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 mounting area. A group of process grooves 4 and a group of internal force elimination grooves 3 are provided on the left, right, upper and lower sides of the base island. 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 on the upper left and lower left, upper right and lower right, respectively.

[0055] The entire lead frame unit adopts a base-island fusion type double-rib structure design. The back of the base island is provided with a base island back extension locking step 16, a base island heat sink extension section locking hole 16-1 and a base island back anti-overflow groove 17 to prevent 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.

[0056] On the top of the UeSSOP56L lead frame body, each group of lead frame units is provided with an anti-reverse hole 5 at the corresponding position to prevent lead frame mixing and reverse sealing during packaging on the production line, which would cause the packaged products to be scrapped.

[0057] The heads of the inner pins 10 in the UeSSOP56L lead frame unit are pin-fused (concave or rectangular), reverse horseshoe-shaped, L-shaped, goose-head side-shaped, sickle-shaped, long strip-shaped, square spade-shaped, or pin base island rib-fused.

[0058] 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 connecting ribs 12 through the lead frame inner pin connection fusion piece 14. The base island mutual fusion type double connecting ribs 12 are connected to the lead frame base island 15, thereby connecting the ground isolation pins 11 to the lead frame base island 15. The ground isolation pins 11 serve as the base island ground wire, and are connected to the base island mutual fusion type double connecting ribs 12 through the lead frame inner pin connection fusion piece 14, forming a small H-shaped pin structure, so that this inner pin has the dual function of serving 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 and the delamination of the product base island, but also ensures the safety of ground wire welding, thereby improving product quality and reliability.

[0059] The connecting ribs on the left and right sides of the lead frame base are designed as a double-rib structure with the base island integrated. The tail ends are designed in a fishtail shape to connect to the lead frame body. The inner pin adhesive film is installed on the long L-shaped inner pins on both sides. This structure not only ensures the coplanarity of the lead frame base and inner pins, and the overall strength of the lead frame, but also effectively controls the deformation of the lead frame during production, transportation, and other aspects. It also ensures the process stability of the product at the bonding and wire bonding stations, ensuring product quality. It solves the problem of lead frame deformation caused by the lead frame transfer process, core loading, and pressure welding, and ensures the wire bonding and plastic encapsulation processes, thereby improving product quality and reliability.

[0060] like Figure 6As shown, by the above structural design, a base island electroplated silver layer 20 with a size corresponding to the chip is arranged at the center of the chip mounting area of the lead frame base island 15, and an inner pin electroplated silver layer 19 is arranged at the head of the pin 10 and the ground wire isolation pin 11 in the lead frame, and the inner pin electroplated silver layer 19 is controlled according to the accuracy of ±0.025 μm; the other areas of the lead frame base island 15, the inner pin 10 and the ground wire isolation pin 11 are bare copper, which aims to improve the reliability and quality of the packaging structure product, prevent the lead frame base island 15 from bonding glue diffusion, cause the product to delaminate, and thus affect the heat dissipation, reliability and quality of the entire packaging structure product.

[0061] The entire lead frame structure is a bent base island (heat sink) outer leakage structure, and the bare copper on the surface of the entire lead frame is treated by an AuAgPdNi+double roughening process. Through the above special structural design and the control of the electroplated silver layer process with an accuracy of ±0.025 μm, the coplanarity of the lead frame base island 15 is ensured, the safety of the isolated ground wire and inner pin wire is ensured, and the quality and reliability of the product are ensured. At the same time, the lead frame base island 15 is connected to the UeSSOP56L lead frame unit 1 main body through the process groove 4, the inner force elimination groove 3, the fish tail-shaped double connecting rib 13 and the base island mutual fusion type double connecting rib 12, which ensures the stability of the entire lead frame structure.

[0062] According to the above Figure 7 The chip bonding position in the die bonding schematic diagram is arranged in the middle of the chip mounting area of the lead frame base island 15, and the high thermal conductivity chip bonding glue 21 is arranged to bond the digital power amplifier chip 22 to the chip mounting area of the lead frame base island 15. According to the above Figure 8 The chip wire mode of the packaging structure in the packaging structure wire schematic diagram is that the RDL metal pad on the surface of the digital power amplifier chip 22 is connected to the strip-shaped inner pin electroplated silver layer 19 on the ground wire isolation pin 11 of the lead frame through the chip wire 23, so as to realize the electrical connection of the packaging structure.

[0063] The second surface of the UeSSOP56L lead frame unit 1, the digital power amplifier chip 22 and the chip wire 23 is externally coated with a plastic encapsulating body 6.

[0064] The RDL metal pads on the surface of the digital power amplifier chip 22 are connected via chip bonding wires 23 to the electroplated silver layer 19 of the heads of the inner leads 10, which are arranged on the four sides of the lead frame island 15 and have heads in the shape of pin fusion (concave or rectangular), reverse horseshoe, L-shaped, goose head side profile, sickle-shaped, long strip, square spade-shaped, or pin-base island fusion rib. This bonding method achieves electrical connection of the entire package structure. Simultaneously, the highly thermally conductive chip bonding adhesive 21 firmly bonds the electroplated silver layer 20 in the center of the lead frame island 15 to the back of the digital power amplifier chip 22, ensuring the dissipation of heat generated by the entire package structure during operation, thereby guaranteeing the quality and reliability of the package structure. By bonding a single digital power amplifier chip to the lead frame unit base island and using thick wire diameter and multiple wire bonding (130 50μm AuPdCu) ​​to electrically connect the RDL metal pad on the chip surface to the pins inside the lead frame, the wire length is reduced, the resistance of the UeSSOP56L package structure is smaller, the on-state current is increased, the heat generation of the package structure is reduced, and the electrical signal suppression capability is improved. 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 usage range of the UeSSOP56L package structure products, and also reducing the packaging cost of the UeSSOP56L package structure.

[0065] The present invention discloses a shrinkable top-heat-dissipating reverse-formed packaging structure with a UeSSOP56L large base island, high power, high heat dissipation, and top-heat-dissipating reverse-formed automotive-grade audio digital power amplifier circuit packaging structure. A large base island of a lead frame packaging structure is provided according to the packaging design process requirements to carry a large-size digital power amplifier chip. The front side of the base island is provided with an electroplated silver layer equivalent to the chip size and a chip bonding glue anti-diffusion groove. The back side of the base island is provided with 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. At the same time, the entire lead frame unit is selectively roughened on both sides. This packaging structure not only meets the product requirements of large-base-island, high-power, top-heat-dissipating products, which is beneficial to the heat dissipation of high-power products, but also blocks the diffusion of adhesive glue on the front of the product base island and plastic packaging material on the back, thereby ensuring and improving the quality and reliability of the product. At the same time, it also ensures 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 requirements of 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 issues. Innovation and optimization are carried out in product frame structure design, frame process processing, inner pin and base island silver plating method, plastic package body pores, production process and flow, thereby improving product production efficiency, reducing product packaging costs, and improving product quality and reliability.

[0066] The UeSSOP56L reverse-molded package meets the needs of modern industry, communications, and automotive sectors. It features low distortion, low noise, wide dynamic range, strong anti-interference and environmental adaptability, high AM / FM reception sensitivity, high output power (4x100W instantaneous output, 4x50W continuous output), low impedance, excellent current linearity, low saturation voltage drop, high efficiency, and thermal short-circuit protection for an audio digital amplifier. This delivers high power, high heat dissipation, and low thermal resistance. Compared to the existing T / SSOP48L single-island lead frame, the UeSSOP56L offers the advantages of high lead frame density, high copper utilization, improved production efficiency, and significant savings in labor and material resources. Furthermore, the UeSSOP56L's large lead frame size allows for high material utilization, enabling it to fulfill the functional requirements of the T / SSOP48L while also replacing the existing T / SSOP48L package. The entire package structure features top-mounted heat dissipation, addressing product PCB space limitations. Based on the package's requirements, a custom thermally enhanced PCB is custom-designed to provide heat dissipation throughout the entire package, ensuring product quality and reliability. See Table 1 for a comparison of lead frame dimensions.

[0067] Table 1 Comparison of dimensions of the present invention's frame and existing frames

[0068]

[0069] Example

[0070] A UeSSOP56L lead frame unit 1 is used to electrically connect 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.

[0071] The UeSSOP56L lead frame unit 1 consists of 4 rows and 10 columns, for a total of 40 lead frame units. Specifically, the frame dimensions of the UeSSOP56L lead frame unit 1 are: length × width × thickness: 251.000 × 67.400 × 0.152 mm; the large unit pitch is 50.199 mm; the small unit pitch is 25.100 mm; the cumulative unit pitch is 225.900 mm; the center distance between the two plastic encapsulation bodies is 25.100 mm; and the distance from the positioning hole to the lead frame corner notch is 12.550 mm at the beginning and 12.550 mm at the end.

[0072] The lead frame base island 15 is distributed with a locking step 16 on the back of the base island with a thickness of T / 2 of the lead frame material thickness, a locking hole 16-1 on the extended cross section of the base island heat sink, and an anti-overflow groove 17 on the back of the base island 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.

[0073] The UeSSOP56L lead frame has a total of 56 inner pins on the top, bottom, left and right sides. Among them, the inner pins 10 and the ground isolation pins 11 of the lead frame are provided with an inner pin electroplating layer 19, and the chip bonding area of ​​the lead frame base island 15 is provided with a base island electroplating silver layer 20.

[0074] The ends of the 56 inner pins on the four sides of the UeSSOP56L lead frame unit (at the distance from the encapsulation line) are all set to an inverted T shape. 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, forming an I-shaped locking structure; the ground 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, forming 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 left and right fishtail-shaped double connecting ribs 13 are connected to the lead frame body through the plastic package 6, and the heads of the left and right fishtail-shaped double connecting ribs 13 are connected to the base island mutual fusion type double connecting rib 12, forming 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.

[0075] like Figure 9 、 Figure 10 As shown, a UeSSOP56L large island high power top heat dissipation reverse forming package structure lead frame core packaging process, the chip thickness 32 of the digital power amplifier chip 22 of 360μm±10μm, according to Figure 9 As shown, place it on the high thermal conductivity adhesive thickness 33 with a wet adhesive thickness of 40μm±5μm, ensuring that the high thermal conductivity adhesive creeping height 34 on the four sides of the digital power amplifier chip 22 is 50% of the chip thickness 32. After the chip is bonded, follow the Figure 10 The schematic requires that the adhesive curing is completed by a five-stage core-on baking curve 35 and a vacuum high-temperature oxygen-free independent exhaust facility baking oven with a five-stage core-on 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 heat sink on the top. In this way, the packaged product after core-on is eliminated through a gentle rising and falling baking process to eliminate the impact of packaging stress on the packaged product after core-on, thereby improving product reliability and quality, and ensuring that the heat generated by the digital power amplifier chip 22 during operation is passed through the large-area heat dissipation pad base island heat sink 18 at the bottom of the UeSSOP56L package structure, thereby effectively transferring the working heat of the digital power amplifier chip 22, forming a good thermal conductivity performance of the package structure.

[0076] like Figure 11 As shown in the figure, the UeSSOP56L large-island high-power top-heat-dissipating reverse-formed package structure lead frame single-chip packaging process of the present invention starts from wafer incoming inspection, goes through multiple manufacturing stations such as dicing and thinning, die-on and die-bonding, and finally completes product packaging and shipment. The intermediate stations and corresponding process requirements form a complete production process flow.

[0077] 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 on it are: four package ejector marks 25 are designed on the front and back of the frame package 24, the small spherical surface 25 on the front is the Pin1 positioning mark, and a large circular plane is designed in the diagonal direction (for distinction from the Pin1 positioning mark). 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 upper colloid bevel surface 29 of the package improves the demoulding property of the package plastic package mold, thereby ensuring the reliability and quality of the plastic package product; the package width 30 (size is 7.50mm), the package pin span 31 (size is 10.30mm), the package length 26 (size is 18.40mm), the package thickness 28 (size is 2.30mm), and the 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.

[0078] The UeSSOP56L large island high-power top heat dissipation reverse-molded package structure lead frame chip package of the present invention has the following processing technology:

[0079] The first step is to conduct corresponding wafer inspection on the customer's incoming wafers according to the wafer inspection standards and requirements. After completion, the qualified customer wafers are input into the packaging department's thinning and scribing station; the thinning and scribing station uses a fully automatic placement machine to automatically place the digital power amplifier chip 22 wafers on an 8-inch or 12-inch film collapse ring; the front of the wafer is affixed with HT-260PG film (UV type), and the debonding is controlled by a parameter of 400 mJ / cm² to eliminate the risk of water ingress and residual adhesive contamination of the wafer during the thinning process. At the same time, according to the UeSSOP56L product packaging requirements, the chip thickness 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 to the thickness control requirement of 360μm±10μm using a fully automatic thinning machine. Then, a fully automatic placement and stripping machine is used to automatically place and strip the thinned digital power amplifier chip 22 wafers. After completion, they are placed in an oven at a temperature of 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 in sequence 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 sequence. During the inspection, the digital power amplifier chips 22 with product quality defects will be marked accordingly so that the subsequent site can accurately identify them during product packaging. After completion, the digital power amplifier chips 22 that have passed the inspection will be transported to the core loading site.

[0080] 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 package structure lead frame of the present invention and place it on the core loading machine transmission guide rail. The lead frame is automatically transferred to the center of the core loading machine workbench by the core loading machine automatic transmission system and automatically clamped. For the UeSSOP56L large base island high-power top heat dissipation reverse forming package structure lead frame package, the glue dispensing robot of the core loading machine is in the chip mounting area on the base island of the UeSSOP56L large base island high-power top heat dissipation reverse forming package structure lead frame unit 1 according to Figure 7 The requirements for the sticking position are as follows: "In a "" shape, draw an appropriate amount of high thermal conductivity chip adhesive 21 in the chip mounting area in turn. The thickness of the high thermal conductivity adhesive 33 is controlled in the range of 40μm±5μm for wet adhesive and 35μm±5μm for dry adhesive. The creeping height 34 of the high thermal conductivity adhesive is controlled in accordance with 50% of the chip thickness 32. A high-precision fully automatic die-bonding machine is used, with a rectangular step-free nozzle and P-150MIC*4 type ejector pins. According to the die-bonding program set before die-bonding and combined with the MAP chip-picking diagram, Figure 7The bonding process requires that one chip from the digital power amplifier chip 22 wafer is placed on the adhesive 21 in sequence, and the required number of bonding products is completed in this order. Then, a five-stage core baking curve 35 and a vacuum high-temperature oxygen-free independent exhaust facility baking oven are used to perform a core bonding one-time curing process. The adhesive is cured by baking in the anti-debonding layer of the high-temperature oven to achieve a firm bond between the chip and the lead frame base island. After baking, the core-bonded product is transported to the pressure welding station for product wire bonding.

[0081] 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 pressure welding to clean the contaminants on the lead frame and digital amplifier chip, thereby improving the quality and reliability of the product during wire welding. Then, a vacuum anti-oxidation pressure welding fixture is used and a fully automatic ultrasonic wire bonding machine is used to follow the UeSSOP56L lead frame package wire bonding diagram. Figure 8 The first surface pad of the digital power amplifier chip is bonded to the pin 10 in the lead frame and the silver-plated layer 19 on the ground isolation pin 11 using multiple 50μm AuPdCu chip bonding wires 23. In this way, the required number of product bonding wires for UeSSOP56L are completed. After the product bonding wires are completed, they are inspected by the three-light % inspection. Products with quality defects are marked next to the lead frame for easy identification at the back-end site, and then sent to the plastic packaging site for product encapsulation.

[0082] 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, digital power amplifier chip 22 and chip bonding wire 23, thereby improving the quality and reliability of the encapsulated product. After that, 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. The encapsulated UeSSOP56L product is then sent to a post-curing high-temperature oven. The UeSSOP56L product is cured in the oven 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 surface of the product colloid 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. The product is then sent to the center rib cutting station for product center rib cutting.

[0083] The fifth step is to use fully automatic rib cutting equipment at the rib cutting station and use 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 glue injection port and the exhaust groove position to form a punched end face, thereby punching the plastic package of the UeSSOP56L package structure from the lead frame unit. 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.

[0084] In the sixth step, the UeSSOP56L lead frame package product completed by the 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.

[0085] In the seventh step, the printing station uses a fully automatic front and back laser marking machine to print the UeSSOP56L lead frame package 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.

[0086] 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. The shape structure is as shown in the front view of the package. Figure 12 , rear view of package Figure 13 , Package right view Figure 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.

[0087] Compared with the existing processing technology of T / SSOP48L lead frame packaging structure, the production method of the present invention adds two-light inspection% inspection process requirements at the reduction site, ensuring the quality and reliability of the products at the reduction site.

[0088] 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 dry adhesive thickness is controlled within the range of 35μm±5μm, and the adhesive creep 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-desorption 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 large chip bonding baking, ensuring that no voids are generated under the chip, and ensuring the product quality and reliability after core loading and bonding.

[0089] 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 lead frame of the multi-wire thickened wire product at the pressure welding station from oxidation, ensuring the quality and reliability after the wire is welded.

[0090] Before plastic sealing, 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 sealing. 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.

[0091] Before cutting the center rib, the cutting station first performs the gate punching action, then cuts the center rib, then performs the lead forming, and finally performs the lead cutting process. This series of process steps not only effectively solves the abnormal tin wire on the end face of the package structure lead frame package, but also meets the process requirements of the 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 cutting and forming, and also fully guarantees the product quality and reliability of the cutting station.

[0092] 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 on the products during the packaging process. The entire process reduces the involvement of personnel, improves product production efficiency, and also ensures product quality.

[0093] After molding, the UeSSOP56L package adopts a top-dissipated heat dissipation structure, which solves the space limitation of the product PCB board surface in the traditional design with the base island heat sink facing downward. 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. The excess power consumption can be diffused to the copper ground plane through the PCB heat dissipation pads and heat dissipation holes, absorbing excess heat, thereby greatly improving the heat dissipation capacity of the chip and ensuring the quality and reliability of the entire packaging structure.

[0094] The above description is merely 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 replacements, and these modifications and replacements 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 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 (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 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 is a packaging structure heat dissipation area for dissipating heat from the packaged product; A plurality of inner pins (10) are arranged around the lead frame base island (15), the plurality of inner pins (10) including an upper left inner pin, an upper right inner pin and other common inner pins, and 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 end 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 isolation pin (11) is provided on the base island mutual fusion type double connection rib structure, and the ground isolation pin (11) is connected to an adjacent connection rib of the base island mutual fusion type double connection rib (12) through a lead frame inner pin connection fusion sheet (14), 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); The back 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); Each group of lead frame units is provided with a gate (7) on the upper right and an exhaust groove (8) on the upper left.

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. Flow channel grooves (2) are provided between each group of lead frame units in the horizontal direction. Internal force elimination grooves (3) are provided on the upper and lower sides of each group of lead frame units in the vertical direction. 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 heads of the inner pins (10) are in the shape of pin mutual fusion, reverse horseshoe, L-shape, goose head side shape, sickle shape, long strip shape, square spade shape, or pin base island rib mutual fusion shape; the inner pins (10) are all 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 mutual fusion type double connecting rib (12) is 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: A base island electroplated silver layer (20) is provided on the lead frame base island (15), an inner pin electroplated silver layer (19) is provided on the inner pin (10), and the corresponding base island electroplated silver layer (20) and inner pin electroplated silver layer (19) are connected by welding wires.

6. 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 pads on the chip surface are electrically connected to the pins (10) in the lead frame by using thick wires and multiple bonding wires.

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

8. A process for manufacturing a shrinkable top heat dissipation reverse-molded packaging structure according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, performing thinning and dicing processing on 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 bonding wire; Step 4, plastic-sealing the welded digital power amplifier chip (22), the lead frame base island (15), the lead frame inner pins (10), the lead frame base island (15) mutually fused double connecting ribs (12), the lead frame fishtail connecting ribs (13), and the inner pins (10) with the outer covering plastic sealing body (6); Step 5, tinning the outer lead frame of the plastic package (6), cutting off the outer pin connecting ribs, and making the product shape according to the size of the package body to form a UeSSOP56L large base island package structure.

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