A tool and method for PGA circuit gold tin sealing

Abstract

The application belongs to the field of semiconductor packaging, and discloses a jig and method for PGA circuit gold-tin fusion sealing. The jig comprises a jig main body and a presser foot structure. The jig main body is provided with a containing area for accommodating a cover plate and a through hollow area for forming a heat convection channel and accommodating a tube shell pin leg. A limiting table is arranged around the periphery of the containing area to limit the horizontal movement of the cover plate and the tube shell. The limiting table is provided with an inclined surface to form a solder overflow gap. The tube shell is invertedly arranged above the cover plate, and the presser foot structure is arranged on the jig main body and corresponds to the limiting table, and is used for applying pressure to a sealing surface. The application realizes accurate positioning of the cover plate and the tube shell by means of the limiting table, and suppresses the assembly deviation of the cover plate. The inclined surface of the limiting table ensures smooth overflow of the molten solder. The hollow area takes into account the protection and uniform heat exchange of the pin leg. The presser foot structure realizes targeted pressure application on the sealing surface, and cooperates with the inverted assembly mode of the tube shell to avoid the entry of excess material into the cavity, solves the existing problems, and improves the gold-tin fusion sealing yield and production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor integrated circuit packaging technology, specifically relating to a tooling and method for gold-tin sealing of PGA circuits, applicable to gold-tin sealed integrated circuits in PGA (pin grid array) package form. Background Technology

[0002] In today's rapidly developing electronics industry, electronic devices are advancing rapidly towards miniaturization, high performance, and multifunctionality. As a key component for achieving electrical connection and physical support between chips and circuit boards, pin grid array (PGA) products, with their high pin density, excellent electrical performance, and heat dissipation advantages, have been widely used in various electronic products, from consumer products such as smartphones and tablets to high-end fields such as servers and aerospace equipment.

[0003] As a key component of pin grid array product packaging, gold-tin bonding is used to tightly bond the chip to the package shell through a specific process (high temperature above 300°C, certain welding pressure and inert atmosphere) to form a sealed space. This protects the chip from external environmental factors (such as moisture, foreign matter, chemicals, etc.) and ensures stable operation of the chip in complex operating environments.

[0004] With the continuous advancement of packaging technology, pin pitch is shrinking and chip integration is constantly increasing. Pin grid array (PGA) products, due to the protruding pins on the circuit shell (either upwards or downwards), cannot be properly sealed using conventional parallel seam soldering rollers. Therefore, PGA products can only be packaged using a fusion sealing process. However, the pins around the solder joint also limit the assembly methods of the fusion sealing process. Gold-tin fusion sealing primarily uses two methods for circuit assembly: clamping the circuit with fixtures or using inverted tooling.

[0005] The clamping method requires the addition of pads to raise the clamping plane, which has problems such as manual alignment of the cover plate, non-targeted force position of the cover plate, and easy introduction of foreign objects when assembling the cover plate with the cavity facing upwards; the inverted tooling requires slots to place the PGA circuit pins, which has problems such as the mold hindering the solder from overflowing, low heat transfer efficiency, and uneven heating of the circuit.

[0006] Both of the aforementioned gold-tin fusion encapsulation methods suffer from inherent, unavoidable issues that result in lower yields and lower production efficiency compared to other encapsulation processes. Details are as follows... Figure 1 As shown.

[0007] To address the limitations of PGA fusion-sealed circuit assembly methods, difficulties in cover plate alignment caused by pads, large offsets, low production efficiency, poor tooling heat transfer efficiency, inability to apply targeted stress, poor solder overflow, and excess material, it is necessary to start with the cover plate assembly process and optimize and improve it. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of misalignment, obstructed solder overflow, and easy entry of foreign matter in existing PGA sealing tooling, and to provide a tooling and method for gold-solder sealing of PGA circuits.

[0009] To achieve the above objectives, the present invention employs the following technical solution: The present invention proposes a tooling for gold-solder bonding of PGA circuits, comprising a tooling body; The fixture body has a receiving area for accommodating the cover plate and a hollow area penetrating the fixture body. The hollow area is used to form a heat convection channel and to accommodate the tube shell pins. A limiting platform is arranged around the receiving area to restrict the horizontal movement of the cover plate and the tube shell. The limiting platform has an inclined surface that forms a solder overflow gap. The tube shell is upside down above the cover plate. The fixture body has a pressure foot structure for applying pressure to the sealing surface of the cover plate. The pressure foot structure is arranged correspondingly to the limiting platform.

[0010] Preferably, the tooling body is made of graphite.

[0011] Preferably, there are eight limiting platforms, which are respectively located at the four corners and the middle of the four sides of the accommodating area.

[0012] Preferably, the angle between the inclined surface and the horizontal direction is 45°, and a solder overflow gap is formed between the inclined surface and the bottom surface of the receiving area.

[0013] Preferably, the presser foot structure has eight presser feet, each presser foot corresponding to a limiting platform.

[0014] Preferably, the eight presser feet are arranged at equal intervals.

[0015] Preferably, when the tube shell is assembled upside down, all the pins at the bottom of the tube shell are retracted into the hollow area, and the pins have no rigid contact with the main body of the tooling.

[0016] Preferably, the depth of the accommodating area is adapted to the thickness of the cover plate.

[0017] Preferably, the hollowed-out area is located in the gap between the limiting platform and the pressure foot structure.

[0018] The present invention proposes an assembly method for a tooling used for gold-solder bonding of PGA circuits, comprising the following steps: Place the main body of the tooling horizontally, with the limiting platform and presser foot structure facing upwards; Place the cover plate within the receiving area and limit its horizontal position using a limiting platform; The tube shell is inverted and placed on top of the cover plate with the sealing weld side facing down. The horizontal position of the tube shell relative to the cover plate is limited by the limiting platform. The tube shell pins are stored in the hollow area to form a combined assembly. The sealing pressure is applied to the assembled body based on the presser foot structure. The tooling is sent into the heating equipment, and the gold and tin are melted and sealed by heat convection formed by the hollow area.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a fixture for gold-solder bonding of PGA circuits. The main body of the fixture is equipped with a receiving area and a surrounding limiting platform. The limiting platform can constrain the horizontal displacement of the cover plate and the tube shell, directly eliminating the cover plate misalignment caused by manual alignment. The limiting platform has an inclined surface to form an overflow gap, allowing molten solder to flow smoothly and solving the problem of solder overflow obstruction. The main body of the fixture has a through-hole area, which not only accommodates the tube shell pins to avoid compression damage, but also forms a three-dimensional heat convection channel, improving the low heat transfer efficiency and uneven heating defects of traditional fixtures. The pressure foot structure is arranged correspondingly to the limiting platform, and the pressure can be accurately transmitted to the key sealing area to achieve targeted multi-point force, making up for the shortcomings of uneven force distribution in traditional assembly. During assembly, the tube shell is inverted on top of the cover plate, with the cavity facing downwards throughout the process, preventing dust and debris from falling into the cavity and eliminating the risk of foreign matter and bonding collisions. The entire structure is integrated and arranged based on the main tooling, with functions such as limiting positioning, overflow guidance, uniform heat exchange, multi-point pressure application, and inverted protection working in tandem. The various structures support each other and work together to solve the technical problems existing in the current technology and improve the yield of melt-sealed products and production efficiency. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This diagram illustrates the problems with the existing assembly methods of the PGA circuit sealing process.

[0022] Figure 2 This is a schematic diagram of a PGA tube shell and matching cover plate sample in an example of the present invention.

[0023] Figure 3 This is a schematic diagram of the tooling structure in an example of the present invention ((a) is a three-dimensional view, (b) is a top view).

[0024] Figure 4 This is a schematic diagram of tooling preparation in an example of the present invention.

[0025] Figure 5 This is a schematic diagram of the tooling placement cover plate in an example of the present invention.

[0026] Figure 6 This is a schematic diagram of the placement of the tooling shell in an example of the present invention.

[0027] Figure 7 This is a schematic diagram of the fixture clamping in an example of the present invention.

[0028] Figure 8 This is a schematic diagram of the 45° cover plate limiting stage of the tooling in an example of the present invention.

[0029] Figure 9 This is an enlarged schematic diagram of the cover plate limiting stage of the tooling in an example of the present invention.

[0030] Figure 10 This is a schematic diagram of the tooling fixture applying pressure in an example of the present invention.

[0031] Figure 11 This is a schematic diagram of the multi-point pressure contact surface of the tooling in an example of the present invention.

[0032] Figure 12 This is a schematic diagram of the tooling inverted placement mode in an example of the present invention.

[0033] Among them, 1-tool body, 2-accommodation area, 3-limiting platform, 4-pressing foot structure, 5-cover plate, 6-tube shell, 7-hollowed-out area, 10-needle leg, 11-sloping surface. Detailed Implementation

[0034] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings: To address the difficulties existing in current fusion-sealing encapsulation methods, this invention provides a multi-point force-bearing fixture for gold-solder fusion sealing of PGA circuits. This fixture employs an independent design, resolving the inherent coplanarity problem of common fixtures. The following describes its application in conjunction with... Figures 2 to 12 Explanation: The present invention proposes a tooling for gold-solder sealing of PGA circuits, comprising a tooling body 1; The fixture body 1 is provided with a receiving area 2 for accommodating the cover plate 5 and a hollow area 7 penetrating the fixture body 1. The hollow area 7 is used to form a heat convection channel and to accommodate the tube shell pin leg. A limiting platform 3 is arranged around the receiving area 2 to restrict the horizontal movement of the cover plate 5 and the tube shell 6. The limiting platform 3 is provided with an inclined surface to form a solder overflow gap. The tube shell 6 is upside down above the cover plate 5. The fixture body 1 is provided with a pressure foot structure 4 for applying pressure to the sealing surface of the cover plate 5. The pressure foot structure 4 is arranged correspondingly to the limiting platform 3. A cover plate 5 is placed in the pre-processed stainless steel fixture body 1 and fixed in position by the limiting platform 3 of the fixture body 1. Then, the tube shell 6 is placed inside. The pressure foot structure 4 is used to apply pressure to the eight pressure foot surfaces of the fixture body 1 to achieve automatic positioning of the cover plate and multi-point force on the sealing surface. The inclined surface is reserved with space for solder overflow. The pressure foot structure 4 transmits sealing pressure at multiple points. The hollow area 7 takes into account both uniform heat exchange and needle leg protection. The various structures cooperate with each other to solve various process defects of traditional fixtures simultaneously.

[0040] The main body of the tooling is made of graphite, with high-purity graphite (purity >99.9%) as its core material. This overcomes the shortcomings of traditional metal materials, such as slow thermal conductivity, low hardness, and easy deformation at high temperatures. It achieves uniform stress distribution during heating. Under long-term high-temperature sealing conditions of 300-350℃, it maintains dimensional stability without thermal deformation or thermal conductivity attenuation, ensuring continuous uniform heating of the sealing surface. It is reusable, extending the tooling's service life and reducing production costs associated with tooling replacement.

[0041] There are eight limiting platforms 3, which are respectively located at the four corners and the middle of the four sides of the accommodating area 2. They can restrict the relative movement of the cover plate and the shell, replacing the traditional manual alignment operation, improving production efficiency, avoiding defects such as local false sealing and sealing voids caused by misalignment, and shortening the alignment time for single-piece assembly.

[0042] The inclined plane forms a 45° angle with the horizontal direction, creating a solder overflow gap between the inclined plane and the bottom surface of the receiving area 2. The 45° inclined plane provides a continuous and unobstructed overflow channel for the molten gold-tin solder, allowing excess liquid solder to flow smoothly outward along the inclined plane during the sealing heating stage without accumulating at the sealing interface. This solves the process problems of traditional tooling sidewalls blocking solder overflow, solder accumulation causing edge protrusion, and airtightness failure.

[0043] The presser foot structure 4 consists of eight presser feet, each corresponding to a limiting platform 3. The eight presser feet cover the four corners and the middle of the four sides of the sealing surface, ensuring that the large-size PGA circuit is subjected to force at multiple points and that the solder flows more evenly.

[0044] The eight pressure feet are evenly spaced to ensure that the force is uniform at all positions on the sealing surface, avoiding damage to the cover plate due to excessive local pressure and sealing defects due to insufficient local pressure, and further optimizing the consistency of pressure distribution.

[0045] When the tube shell 6 is assembled upside down, all the pins at the bottom of the tube shell 6 are retracted into the hollow area 7, and the pins have no rigid contact with the main body of the tooling 1.

[0046] The depth of the receiving area 2 is matched with the thickness of the cover plate 5. After the cover plate 5 is placed, the top surface is at a uniform height and there will be no misalignment, ensuring that the pressure foot structure 4 is subjected to uniform force when applying pressure. At the same time, it works with the surrounding limiting platform 3 to complete bidirectional limiting, further enhancing the positioning accuracy of the cover plate.

[0047] The hollowed-out area 7 ensures uniform heating of the PGA circuit in various heating devices such as hot air and heat pipes, reducing heat loss during heat conduction. Distributed in the gap between the limiting platform 3 and the pressure foot structure 4, it forms a multi-dimensional heat convection channel, reducing heat loss during heat conduction, ensuring consistent temperature distribution on the soldering surface, and significantly improving the uniformity of solder melting and flow.

[0048] This invention proposes an assembly method for a fixture used for gold-solder bonding of PGA circuits. The method employs a top-and-bottom insertion technique, avoiding the risk of introducing excess material upwards into the PGA circuit cavity and accidentally touching the bonding wires. Taking the PGA391 pin-grid array transistor shell and its matching gold-plated Kovar cover plate as an example, the specific design and assembly method of this fixture include the following steps, illustrated in the schematic diagram below. Figures 4 to 10 .

[0049] Step 1: Place the main body of the tooling 1 flat on the table, with the 8 limiting platforms 3 facing upwards.

[0050] Step 2: Place the matching cover plate 5 with the side with the solder ring facing up into the fixture body 1.

[0051] Step 3: Place the PGA391 pipe shell 6 with the welded side facing down on the cover plate 5.

[0052] Step 4: Clamp the tooling foot on one side of the clamping plane and the bottom of the tube shell on the other side.

[0053] Step 5: Repeat steps one through four above to assemble the circuits one by one.

[0054] The highlights of this invention include a 45° cover plate limiting stage 3, allowing solder to overflow normally; multi-point pressure contact surfaces for targeted pressure application by the fixture; and an inverted placement mode to prevent the introduction of foreign matter and accidental contact with the bonding wire. Specifically, as follows... Figures 8 to 12 As shown.

[0055] Protecting the upright needles on the tube shell surface from damage includes the following steps: Step 1: Place the main body of the tooling 1 horizontally, with the limiting platform 3 and the pressure foot structure 4 facing upwards; Step 2: Place the cover plate 5 in the receiving area 2, and limit the horizontal position of the cover plate 5 by the limiting platform 3; Step 3: Place the tube shell 6 upside down on top of the cover plate 5 with the sealing weld side facing down. The horizontal position of the tube shell 6 relative to the cover plate 5 is limited by the limiting platform 3. The tube shell pins are stored in the hollow area 7 to form a combined assembly. Step 4: Apply sealing pressure to the assembled body based on the pressure foot structure 4, and send the tooling into the heating equipment. The gold and tin are melted by heat convection formed by the hollow area 7.

[0056] Therefore, this invention proposes a fixture for gold-solder sealing of PGA circuits. The fixture's built-in eight limiting platforms fix the cover plate position, solving the problem of cover plate misalignment during traditional manual operation. The 45° beveled bottom of the limiting platforms ensures space for solder overflow, allowing the casing to be placed inside, and the casing is then fixed by the fixture's outer perimeter. Pressure is applied to the surfaces of the eight pressure feet of the fixture by the clamps, transmitting force to the four corners and the middle of the four sides of the sealing surface. This achieves the purpose of limiting the position between the cover plate and the casing and ensuring targeted force application at multiple points on the sealing surface, resulting in more uniform solder flow. The circuit cavity is kept facing downwards throughout the process, avoiding the risk of introducing foreign objects and accidentally touching the internal bonding wires. The fixture's hollow design ensures uniform heating of the PGA circuit in different heat source devices, and the hollow area forms a dynamic heat convection channel, reducing heat loss during heat conduction. This fixture significantly improves the production efficiency of gold-solder sealing, achieving cost reduction and efficiency improvement, and creating greater economic benefits for enterprises.

[0057] This invention can be widely applied in the field of gold-tin fusion encapsulation of pin-gate array (PGA) integrated circuits. To clearly illustrate the invention, specific examples are described below. These examples are only a portion, not all, of the invention. Furthermore, the casing used in this example is a PGA391 pin-gate array package, the cover is a matching gold-plated Kovar alloy, and the substrate material of the tooling is high-purity graphite (purity >99.9%).

[0058] The present invention has the following advantages: 1) High-purity graphite (purity > 99.9%) is used as the tooling material. Compared with traditional stainless steel, it has advantages such as high hardness, good thermal conductivity, high temperature resistance, and oxidation resistance, making it an excellent material for manufacturing this tooling.

[0059] 2) The four-sided limiting platforms of the PGA tooling fix the relative movement between the cover plate and the tube shell, replacing the manual alignment of the cover plate and tube shell, improving the assembly speed and thus increasing production efficiency, and eliminating the problem of the cover plate's position shifting on the tube shell. At the same time, the 45° beveled surface at the bottom of the limiting platform ensures space for solder overflow, preventing the solder from being obstructed.

[0060] 3) PGA products are relatively large. This tooling adopts the assembly sequence of placing the cover plate first and then the tube shell, which replaces the manual assembly process and avoids the problems of introducing foreign objects and accidentally touching the bonding wires in the traditional cavity-up assembly method.

[0061] 4) The eight pressure feet of this fixture cover the four corners and four sides of the PGA circuit sealing surface, realizing the purpose of multi-point force on the cover plate. This ensures that different positions of the cover plate can be subjected to targeted force. The force of each pressure foot can be adjusted by different types of clamps, avoiding insufficient pressure at the four corners due to the inability to change the pressure distribution position, thus preventing the formation of voids at the four corners.

[0062] 5) This fixture adopts a hollow design, and the hollow area forms a dynamic heat convection channel, which changes the heat flow path from the traditional unidirectional conduction to multi-dimensional three-dimensional conduction, resulting in a more uniform heat distribution compared to traditional fixtures. At the same time, the hollow design protects the upright needles on the tube surface from damage.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A tooling for gold-solder bonding of PGA circuits, characterized in that, Including the main tooling body (1); The tooling body (1) is provided with a receiving area (2) for accommodating the cover plate (5) and a hollow area (7) penetrating the tooling body (1). The hollow area (7) is used to form a heat convection channel and to receive the tube shell pin leg. A limiting platform (3) is arranged around the periphery of the receiving area (2) to limit the horizontal movement of the cover plate (5) and the tube shell (6). The limiting platform (3) is provided with an inclined surface to form a solder overflow gap. The tube shell (6) is upside down and placed above the cover plate (5). The tooling body (1) is provided with a pressure foot structure (4) for applying pressure to the sealing surface of the cover plate (5). The pressure foot structure (4) is arranged correspondingly to the limiting platform (3).

2. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, The tooling body (1) is made of graphite.

3. The tooling for gold-solder bonding of PGA circuits according to claim 1, characterized in that, The limiting platform (3) is provided in eight positions, and the eight limiting platforms (3) are respectively located at the four corners and the middle of the four sides of the accommodating area (2).

4. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, The angle between the inclined surface and the horizontal direction is 45°, and a solder overflow gap is formed between the inclined surface and the bottom surface of the accommodating area (2).

5. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, The presser foot structure (4) consists of eight presser feet, each of which corresponds to a limiting platform (3).

6. The tooling for gold-solder sealing of PGA circuits according to claim 5, characterized in that, The eight presser feet are set at equal intervals.

7. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, When the tube shell (6) is assembled upside down, all the pins at the bottom of the tube shell are retracted into the hollow area (7), and the pins have no rigid contact with the main body of the tooling (1).

8. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, The depth of the accommodating area (2) is adapted to the thickness of the cover plate (5).

9. The tooling for gold-solder sealing of PGA circuits according to claim 1, characterized in that, The hollow area (7) is located in the gap between the limiting platform (3) and the presser foot structure (4).

10. An assembly method for a tooling used for gold-solder sealing of PGA circuits, characterized in that, The tooling for gold-solder sealing of PGA circuits according to any one of claims 1 to 9 includes the following steps: Place the tooling body (1) horizontally, with the limiting platform (3) and presser foot structure (4) facing upwards; Place the cover plate (5) in the receiving area (2) and limit the horizontal position of the cover plate (5) by the limiting platform (3); The tube shell (6) is inverted and placed above the cover plate (5) with the sealing surface facing down. The horizontal position of the tube shell (6) relative to the cover plate (5) is limited by the limiting platform (3). The tube shell pins are stored in the hollow area (7) to form a combined assembly. Based on the presser foot structure (4), the sealing pressure is applied to the combined assembly. The tooling is sent into the heating equipment, and the gold and tin are melted by heat convection formed by the hollow area (7).

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