A solder ball, ball grid array, chip, and pad

Abstract

The application provides a solder ball, a ball grid array, a chip and a pad, relates to the technical field of solder balls, and the cross section of the solder ball comprises a rectangular area, a first semicircular area and a second semicircular area; a first side of the rectangular area is connected with a straight side of the first semicircular area, and a second side of the rectangular area is connected with a straight side of the second semicircular area. Since the cross section is parallel to the pad, and the length of the cross section along the force direction of the solder ball is greater than the length of the cross section along other directions except the force direction of the solder ball, that is, the length of the cross section of the solder ball in the force direction of the solder ball is the longest, compared with the isotropic material mechanical properties of the spherical solder ball in the related art, the maximum stress generated by the solder ball under force can be reduced, the adaptability to the force in a specific direction is better, the possibility of damage of the spherical solder ball due to excessive stress can be reduced, and the success rate of the ball grid array package is improved.

Description

Technical Field

[0001] This application belongs to the field of solder ball technology, specifically relating to a solder ball, ball grid array, chip, and solder pad. Background Technology

[0002] During the manufacturing and use of packaging substrates and printed circuit boards (PCBs), solder balls are subjected to forces in specific directions.

[0003] In related technologies, solder balls are spherical. The mechanical properties of spherical solder balls are isotropic, which makes them poorly adaptable to forces in a specific direction. This leads to excessive stress on the spherical solder balls, causing them to break and resulting in failure of the ball grid array (BGA) packaging of the chip. Summary of the Invention

[0004] This application aims to provide a solder ball, a ball grid array, a chip, and a pad, at least to solve the problem in the related art that the material mechanical properties of spherical solder balls are isotropic and have poor adaptability to forces in a specific direction, resulting in excessive stress on the spherical solder balls and damage, and failure of the ball grid array packaging of the chip.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application provide a solder ball, the cross-section of which includes a rectangular region, a first semicircular region, and a second semicircular region, the cross-section being parallel to the solder pad; The first side of the rectangular region is connected to the straight side of the first semicircular region, and the second side of the rectangular region is connected to the straight side of the second semicircular region; Wherein, the length of the cross section along the direction of force on the solder ball is greater than the length of the cross section along other directions besides the direction of force on the solder ball.

[0006] Optionally, the first side and the second side are arranged opposite each other, and the third side and the fourth side of the rectangular region are arranged opposite each other; the length of the third side and the length of the fourth side are both less than or equal to a preset threshold; wherein, the preset threshold is the product of the diameter of the first semicircular region and a first preset value or the product of the diameter of the second semicircular region and the first preset value.

[0007] Optionally, the length of the third side ranges from 0.25 mm to 0.5 mm; the length of the fourth side ranges from 0.25 mm to 0.5 mm.

[0008] Optionally, the first side completely coincides with the straight edge of the first semicircular region, and / or the second side completely coincides with the straight edge of the second semicircular region.

[0009] Optionally, the first semicircular region and the second semicircular region have the same shape and size.

[0010] Optionally, the line connecting the midpoint of the first side and the midpoint of the second side is in the same direction as the direction of the force.

[0011] Optionally, the area of ​​the cross-section ranges from 0.35 square millimeters to 0.5 square millimeters.

[0012] Optionally, the radius of the first semicircular region ranges from 0.2 mm to 0.3 mm, and / or the radius of the second semicircular region ranges from 0.2 mm to 0.3 mm.

[0013] Optionally, the thickness of the solder ball ranges from 0.55 mm to 0.65 mm.

[0014] Secondly, embodiments of this application provide a ball grid array, including a plurality of solder balls as described in the first aspect, wherein the solder balls in the ball grid array are arranged in an array.

[0015] Optionally, the square root of the ratio of the area of ​​the cross section to π is less than or equal to the product of the center distance between adjacent solder balls and a second preset value.

[0016] Thirdly, embodiments of this application provide a chip including solder balls as described in the first aspect, or including a ball grid array as described in the second aspect.

[0017] Fourthly, embodiments of this application provide a solder pad whose shape is similar to the shape of the cross-section, the solder pad being used for soldering to solder balls as described in the first aspect.

[0018] In this embodiment, the cross-section of the solder ball includes a rectangular region, a first semicircular region, and a second semicircular region. The first side of the rectangular region is connected to the straight side of the first semicircular region, and the second side of the rectangular region is connected to the straight side of the second semicircular region. Since the cross-section is parallel to the pad and the length of the cross-section along the direction of force on the solder ball is greater than the length of the cross-section along other directions besides the direction of force on the solder ball, that is, the length of the cross-section of the solder ball is the longest in the direction of force on the solder ball. Compared with the isotropic material mechanical properties of spherical solder balls in related technologies, this can reduce the maximum stress generated by the solder ball under force, thereby improving its adaptability to forces in a specific direction, reducing the possibility of excessive stress and breakage of the spherical solder ball, and improving the success rate of ball grid array packaging of chips. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0020] Figure 1 This is a schematic diagram of the cross-section of a solder ball provided in an embodiment of this application; Figure 2 This is a schematic diagram of a solder ball provided in an embodiment of this application; Figure 3 This is a schematic diagram of the cross-section of another solder ball provided in an embodiment of this application; Figure 4 This is a schematic diagram of the cross-section of another type of solder ball provided in an embodiment of this application; Figure 5 This is a schematic diagram of the cross-section of the three types of solder balls provided in the embodiments of this application; Figure 6 This is a schematic diagram of a simulation experiment result provided in an embodiment of this application.

[0021] Figure label: 10 - Rectangular area; 11 - First side; 111 - Midpoint of the first side; 12 - Second side; 121 - Midpoint of the second side; 13 - Third side; 14 - Fourth side; 20 - First semicircular area; 30 - Second semicircular area; 40 - Direction of force; A1 - Solder ball; A1a - Cross section; A1b - First point; A1c - Second point; A2 - Packaging substrate; A3 - Solder resist layer on the packaging substrate; A4 - Solder pad on the circuit board; A5 - Solder resist layer on the circuit board; A6 - Circuit board. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] Reference Figure 1This application provides a solder ball A1, the cross-section A1a of which includes a rectangular region 10, a first semicircular region 20, and a second semicircular region 30, the cross-section A1a being parallel to the solder pad; the first side 11 of the rectangular region 10 is connected to the straight side of the first semicircular region 20, and the second side 12 of the rectangular region 10 is connected to the straight side of the second semicircular region 30; wherein, the length of the cross-section A1a along the force direction 40 of the solder ball A1 is greater than the length of the cross-section A1a along other directions other than the force direction 40 of the solder ball A1.

[0025] In some embodiments, the pads include pads on circuit board A6, pads on chip packaging substrate A2, etc.

[0026] In some embodiments, cross section A1a includes a plane cut between the bottom and top surfaces of solder ball A1.

[0027] In some embodiments, the bottom surface of solder ball A1 has the same shape and size as the cross-section A1a of solder ball A1.

[0028] In some embodiments, the top surface of solder ball A1 has the same shape and size as the cross section A1a of solder ball A1.

[0029] In some embodiments, each cross section A1a of the solder ball A1 has the same shape and size.

[0030] In some embodiments, each longitudinal section of the solder ball A1 is rectangular, wherein the longitudinal section is perpendicular to the solder pad.

[0031] In some embodiments, the bottom surface of solder ball A1 is parallel to the cross-section A1a of solder ball A1.

[0032] In some embodiments, the top surface of solder ball A1 is parallel to the cross-section A1a of solder ball A1.

[0033] Reference Figure 2 In some embodiments, solder ball A1 is disposed between the pad (not shown in the figure) on the chip packaging substrate A2 and the pad on the circuit board A6, wherein the solder resist layer A3 on the packaging substrate A2 is disposed on the side of the pad on the packaging substrate A2, and the solder resist layer A5 on the circuit board A6 is disposed on the side of the pad A4 on the circuit board A6.

[0034] In some embodiments, the material type of solder ball A1 includes lead-tin alloy, lead-free solder alloy, high-temperature solder alloy, gold-tin solder, tin-silver-copper alloy, plastic core solder ball, tin-bismuth alloy, tin-nickel alloy, or copper, etc.

[0035] Among them, lead-tin alloy solder balls A1 have good soldering performance and strength, and relatively low cost, making them one of the commonly used BGA solder ball A1 materials in the early days; lead-free solder alloys have high strength and good fatigue resistance, meet environmental protection requirements, and can better resist fatigue damage caused by thermal stress, thereby improving the long-term reliability of BGAs. They are widely used in electronic products with high reliability requirements, such as servers, high-end graphics cards, and automotive electronics; high-temperature solder alloys have good electrical and thermal conductivity, as well as excellent corrosion resistance and oxidation resistance, and can withstand high-temperature environments, making them suitable for electronic devices operating in specific environments; gold-tin solder has good electrical and thermal conductivity, high soldering strength, and can withstand large mechanical stress and thermal cycling stress. It is often used in chip packaging with extremely high reliability requirements, such as BGA packaging of high-performance graphics processing units (GPUs) and field-programmable gate arrays (FPGAs). Tin-silver-copper alloys exhibit superior performance among lead-free solders, possessing excellent wettability, strength, and fatigue resistance. They effectively reduce soldering defects and improve soldering quality, making them suitable for products with stringent environmental and reliability requirements, such as computers and communication equipment. Plastic-core solder beads, with their plastic core encapsulated in solder, have a lower density, reducing package weight and costs to some extent. They can be used in BGA packages for weight-sensitive portable electronic products, such as mobile phones and tablets. Tin-bismuth alloys offer good wettability and a certain level of strength, maintaining stable performance at low temperatures. They are suitable for electronic devices operating at low temperatures or where soldering temperature requirements are stringent. In low-temperature applications, such as certain cryogenic storage devices and partial packaging of consumer electronics, tin-nickel alloys are used. These alloys offer excellent corrosion resistance and oxidation resistance, stable welding performance, and the formation of strong solder joints. They perform exceptionally well in harsh environments such as high humidity and high salt spray, and are commonly used in BGA packaging for outdoor electronic devices and industrial control equipment where environmental adaptability is critical. Copper solder balls A1 possess excellent electrical and thermal conductivity and high strength, providing good electrical and heat dissipation performance. In some high-performance, high-power chip packages, such as high-end CPUs and GPUs, copper solder balls A1 can be used to achieve effective connection and heat dissipation between the chip and the packaging substrate A2.

[0036] In this embodiment, the cross-section A1a of the solder ball A1 includes a rectangular region 10, a first semicircular region 20, and a second semicircular region 30. The first side 11 of the rectangular region 10 is connected to the straight side of the first semicircular region 20, and the second side 12 of the rectangular region 10 is connected to the straight side of the second semicircular region 30. Since the cross-section A1a is parallel to the pad and the length of the cross-section A1a along the force direction 40 of the solder ball A1 is greater than the length of the cross-section A1a along other directions other than the force direction 40 of the solder ball A1, that is, the length of the cross-section A1a of the solder ball A1 is the longest in the force direction 40 of the solder ball A1, compared with the isotropic material mechanical properties of spherical solder balls in related technologies, the maximum stress generated by the solder ball A1 under force can be reduced, thereby improving the adaptability to force in a specific direction, reducing the possibility of excessive stress and breakage of the spherical solder ball, and improving the success rate of ball grid array packaging of chips.

[0037] Optional, refer to Figure 3 In some embodiments, the first side 11 and the second side 12 are arranged opposite to each other, and the third side 13 and the fourth side 14 of the rectangular region 10 are arranged opposite to each other; the length of the third side 13 and the length of the fourth side 14 are both less than or equal to a preset threshold; wherein, the preset threshold is the product of the diameter of the first semicircular region 20 and a first preset value or the product of the diameter of the second semicircular region 30 and the first preset value.

[0038] In some embodiments, the length of the first side 11 and the length of the second side 12 are both equal to the diameter of the first semicircular region 20.

[0039] In some embodiments, the length of the first side 11 and the length of the second side 12 are both equal to the diameter of the second semicircular region 30.

[0040] In some embodiments, the first preset value is 2.

[0041] Reference Figure 4 In some embodiments, the length of the third side 13 and the length of the fourth side 14 are both a, and the radius of the first semicircular region 20 and the radius of the second semicircular region 30 are both R. In order to meet the actual production and manufacturing constraints of the chip, the value range of a is set to (0, 2R).

[0042] Reference Figure 5 In some embodiments, the shape of the solder ball A1 is changed by setting the distance 'a' between the first side 11 and the second side 12, thereby controlling the lengths of the third side 13 and the fourth side 14. Furthermore, the length of the cross-section A1a along the force direction 40 of the solder ball A1 can be adjusted. Specifically, increasing 'a' increases the length of the cross-section A1a along the force direction 40 of the solder ball A1, while decreasing 'a' decreases the length of the cross-section A1a along the force direction 40 of the solder ball A1. For example... Figure 5 In (b1), the cross-section A1a of the solder ball A1 is smaller than a. Figure 5 (b2) The cross-section A1a of the solder ball A1, a, Figure 5 In (b2), the cross-section A1a of the solder ball A1 is smaller than a. Figure 5 In (b3), the cross section A1a of the solder ball A1 is such that a... Figure 5 (b1) The length of the cross section A1a along the force direction 40 of the solder ball A1 is less than Figure 5 (b2) The length of cross section A1a along the force direction 40 of solder ball A1, and Figure 5 (b2) The length of the cross section A1a along the force direction 40 of the solder ball A1 is less than Figure 5 (b3) The length of the cross section A1a along the force direction of the welding ball A1 is 40.

[0043] In this embodiment of the application, by setting the length of the third side 13 and the length of the fourth side 14 to be less than or equal to a preset threshold, wherein the preset threshold is the product of the diameter of the first semicircular region 20 and the first preset value or the product of the diameter of the second semicircular region 30 and the first preset value, the shape of the solder ball A1 and the length of the cross section A1a along the force direction 40 of the solder ball A1 can be controlled.

[0044] Optionally, in some embodiments, the length of the third side 13 ranges from 0.25 mm to 0.5 mm; the length of the fourth side 14 ranges from 0.25 mm to 0.5 mm, for example, the length of both the third side 13 and the fourth side 14 is 0.046 mm.

[0045] In this embodiment of the application, by setting the lengths of the third side 13 and the fourth side 14 within a preset length range, the shape of the solder ball A1 can be controlled and the length of the cross section A1a along the force direction 40 of the solder ball A1 can be adjusted.

[0046] Optionally, in some embodiments, the first side 11 completely coincides with the straight edge of the first semicircular region 20, and / or the second side 12 completely coincides with the straight edge of the second semicircular region 30.

[0047] In some embodiments, the length of the first side 11 is equal to the diameter of the first semicircular region 20.

[0048] In some embodiments, the length of the second side 12 is equal to the diameter of the second semicircular region 30.

[0049] In this embodiment, since the first side 11 completely coincides with the straight edge of the first semicircular region 20, the graphic boundary at the junction of the rectangular region 10 and the first semicircular region 20 is smooth, which can reduce the stress generated at the boundary of the solder ball A1 after it is subjected to force. Similarly, since the second side 12 completely coincides with the straight edge of the second semicircular region 30, the graphic boundary at the junction of the rectangular region 10 and the second semicircular region 30 is smooth, which can reduce the stress generated at the boundary of the solder ball A1 after it is subjected to force.

[0050] Optionally, in some embodiments, the first semicircular region 20 and the second semicircular region 30 have the same shape and size.

[0051] In some embodiments, the length of the radius of the first semicircular region 20 is equal to the length of the radius of the second semicircular region 30.

[0052] In this embodiment, since the first semicircular region 20 and the second semicircular region 30 have the same shape and size, the two sides of the solder ball A1 are symmetrical, which helps to reduce the stress generated after the solder ball A1 is subjected to force.

[0053] Optionally, in some embodiments, the line connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is in the same direction as the force direction 40.

[0054] In some embodiments, the midpoint 111 of the first side 11 coincides with the center of the first semicircular region 20, the midpoint 121 of the second side 12 coincides with the center of the second semicircular region 30, the line connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is perpendicular to the straight edge of the first semicircular region 20, and the line connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is perpendicular to the straight edge of the second semicircular region 30.

[0055] In this embodiment, since the line connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is in the same direction as the force direction 40, the length of the cross section A1a in the direction connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is greater than the length of the cross section A1a in other directions other than the force direction 40 of the solder ball A1. That is, the length of the cross section A1a in the direction connecting the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12 is the longest, which can reduce the stress generated after the solder ball A1 is subjected to force.

[0056] Optionally, in some embodiments, the area of ​​the cross section A1a ranges from 0.35 square millimeters to 0.5 square millimeters.

[0057] For example, the area of ​​cross section A1a is 0.45 square millimeters.

[0058] In this embodiment, the area of ​​cross-section A1a is controlled to be between 0.35 square millimeters and 0.5 square millimeters to meet the chip packaging requirements.

[0059] In some embodiments, the area of ​​cross section A1a is expressed as:

[0060] Where S is the area of ​​cross section A1a, the length of the third side 13 and the length of the fourth side 14 are both a, and the radius of the first semicircular region 20 and the radius of the second semicircular region 30 are both R.

[0061] Optionally, in some embodiments, the radius of the first semicircular region 20 ranges from 0.2 mm to 0.3 mm, and / or the radius of the second semicircular region 30 ranges from 0.2 mm to 0.3 mm.

[0062] For example, the radius of the first semicircular region 20 is 0.25 mm, and the radius of the second semicircular region 30 is 0.25 mm.

[0063] In this embodiment of the application, the length range of the radius of the first semicircular region 20 is set to 0.2 mm to 0.3 mm, and the length range of the radius of the second semicircular region 30 is set to 0.2 mm to 0.3 mm, in order to meet the chip packaging requirements.

[0064] Optionally, in some embodiments, the thickness h of the solder ball A1 ranges from 0.55 mm to 0.65 mm.

[0065] In some embodiments, the thickness h of solder ball A1 is the length of solder ball A1 in the direction perpendicular to the solder pad.

[0066] For example, the thickness h of solder ball A1 is 0.6 mm.

[0067] In this embodiment, the thickness h of the solder ball A1 is set to a range of 0.55 mm to 0.65 mm to meet the chip packaging requirements.

[0068] This application provides a ball grid array, including a plurality of solder balls A1 as described above. The solder balls A1 in the ball grid array are arranged in an array. The specific implementation process of the solder balls A1 is similar to that described above, and will not be repeated here.

[0069] Ball grid array (BGA) is a packaging technology primarily used for high-density electronic chip packaging. It achieves electrical connection to the PCB by arranging spherical solder points on the bottom of the chip in an array. It offers advantages such as high-density input / output (I / O) connections, good electrical performance, and heat dissipation. BGA packaging is widely used in the packaging of complex chips such as CPUs and GPUs.

[0070] In some embodiments, each solder ball A1 in the ball grid array has the same shape and size.

[0071] In some embodiments, the arrangement of solder balls A1 in the ball grid array includes uniform arrangement, staggered arrangement, peripheral arrangement, rectangular arrangement, local array arrangement, etc.

[0072] The solder balls A1 are uniformly arranged as follows: solder balls A1 are evenly distributed on the bottom of the packaging substrate A2 in a regular square or rectangular grid, with equal row and column spacing. The advantages of this arrangement are symmetrical and regular layout, which facilitates processing, manufacturing, and quality control. It can achieve good electrical performance and mechanical stability and is suitable for most conventional BGA packaging applications, such as common computer motherboard chip packaging. The staggered arrangement of solder balls A1 means that solder balls A1 are arranged in an alternating manner, that is, adjacent rows or columns of solder balls A1 are staggered by a certain distance. This staggered arrangement can, to some extent, increase the distribution density of solder balls A1, increase the number of input / output pins, and also improve the uniformity and reliability of signal transmission, while reducing signal interference. It is commonly used in BGA packages where high signal transmission performance is required, such as high-end graphics card chip packages. The solder balls A1 are arranged in a circular array around the periphery of the package substrate A2. This arrangement leaves space in the center of the chip for other purposes, such as placing heat dissipation components or internal wiring. It is suitable for BGA packages with special requirements for chip heat dissipation or those that need optimized internal space layout, such as some high-performance processor packages. The solder balls A1 are arranged in a rectangular array with unequal row and column spacing, which can be adjusted according to specific requirements. This rectangular arrangement better accommodates packaging substrates A2 of different shapes and sizes, and meets specific pin layout requirements, providing greater flexibility for chip packaging design. It is commonly used in the packaging of some specially shaped electronic devices.

[0073] The local array arrangement of solder balls A1 is as follows: solder balls A1 are only arrayed in a local area of ​​the package substrate A2, while other areas have no solder balls A1 or the solder balls A1 are sparsely distributed. This arrangement method can be used to strategically place solder balls A1 according to the functional partitions and pin usage of the chip, thereby optimizing the package structure and performance. It is suitable for chip packages with specific functional modules, such as RF chips and memory chips.

[0074] Optionally, in some embodiments, the square root of the ratio of the area of ​​the cross section A1a to π is less than or equal to the product of the center distance between adjacent solder balls A1 and a second preset value.

[0075] In some embodiments, the center-to-center distance between adjacent solder balls A1 is the distance between the geometric centers of adjacent solder balls A1.

[0076] In some embodiments, the second preset value is 2 / 5.

[0077] In some embodiments, if the area of ​​the cross-section A1a of the solder ball A1 is equivalent to the area of ​​a circle, then:

[0078] Where S is the area of ​​the cross section A1a of the solder ball A1, D is the diameter of the equivalent circle, the length of the third side 13 and the length of the fourth side 14 are both a, and the radius of the first semicircular region 20 and the radius of the second semicircular region 30 are both R.

[0079] Therefore, we can conclude that:

[0080] To meet the limitations of actual chip production and manufacturing, D must be less than or equal to 80% of the center distance between adjacent solder balls A1. When D is less than or equal to 80% of the center distance between adjacent solder balls A1, then:

[0081] Right now:

[0082] Also:

[0083] Where d is the center distance between adjacent solder balls A1.

[0084] For example, when d is 1 mm, R can be 0.023 mm and a can be 0.046 mm.

[0085] In this embodiment of the application, by controlling the square root of the ratio of the area of ​​cross section A1a to π to be less than or equal to the product of the center distance of adjacent solder balls A1 and a second preset value, the actual production and manufacturing constraints of the chip are met.

[0086] This application provides a chip including solder balls A1 as described above, or including a ball grid array as described above. The specific implementation process of solder balls A1 is similar to that described above, and will not be repeated here.

[0087] In some embodiments, the types of chips include central processing units (CPUs), graphics processing units, high-speed communication chips, network processors, tablet chips, smartwatch chips, field-programmable gate arrays, application-specific integrated circuit (ASIC) chips, memory chips, etc.

[0088] This application provides a solder pad whose shape is similar to the shape of the cross-section A1a of the solder ball A1. The solder pad is used to solder the solder ball A1 as described above. The specific implementation process of the solder ball A1 is similar to that described above, and will not be repeated here.

[0089] In some embodiments, pads are arranged in an array on circuit board A6 to form a pad array. The pads in the pad array correspond to the solder balls A1 in the ball grid array, and the solder balls A1 are soldered to the pads corresponding to the solder balls A1.

[0090] In some embodiments, the arrangement of pads in the pad array includes uniform arrangement, staggered arrangement, peripheral arrangement, rectangular arrangement, local array arrangement, and centrally symmetrical arrangement with edge compensation.

[0091] The uniform arrangement of the pads is as follows: the pads are evenly distributed on the A6 printed circuit board (PCB) in a regular square or rectangular grid, with equal row and column spacing. The advantages of this arrangement are symmetrical and regular layout, ease of manufacturing and quality control, good electrical performance and mechanical stability, and suitability for most common BGA packaging applications, such as common computer motherboard chip packaging. The staggered arrangement of pads refers to the arrangement of pads in an alternating manner, meaning that pads in adjacent rows or columns are staggered by a certain distance. This staggered arrangement can increase pad density and the number of I / O pins to some extent, while also improving the uniformity and reliability of signal transmission and reducing signal interference. It is commonly used in BGA packages where high signal transmission performance is required. The pads are arranged in a circular array around the perimeter of the PCB. This arrangement leaves space in the center of the chip for other purposes, such as placing heat dissipation components or internal wiring. It is suitable for BGA packages with special requirements for chip heat dissipation or those that need optimized internal space layout. The pads are arranged in a rectangular array with unequal row and column spacing, which can be adjusted according to specific needs. This rectangular arrangement better adapts to different shapes and sizes of package substrates (A2) and meets specific pin layout requirements, providing greater flexibility for chip packaging design. It is commonly used in packages of some special-shaped electronic devices. The local array arrangement of pads refers to the arrangement of pads only in a local area of ​​the PCB, while other areas have no pads or have sparsely distributed pads. This arrangement method allows for targeted pad layout based on the functional partitioning and pin usage of the chip, optimizing the package structure and performance. It is suitable for chip packages with specific functional modules, such as RF chips and memory chips. For large BGAs (over 20 mm × 20 mm), a center-symmetric + edge-compensated pad arrangement is recommended. The central area pads are arranged symmetrically to ensure soldering stability; meanwhile, appropriate compensation design is implemented in the edge areas to improve the connection reliability of the edge pads. This approach is suitable for larger BGA packages.

[0092] In some embodiments, the welding process for welding the spherical grid array onto the pad array includes reflow soldering, vapor phase reflow soldering, laser reflow soldering, manual soldering, and ball placement.

[0093] The reflow soldering process includes the following steps: (1) Cleaning and pretreatment: Before soldering, the pads of the printed circuit board A6 (PCB) and BGA chip need to be cleaned to remove oxide layers and contaminants to ensure good soldering results. Special cleaning agents and tools can be used for treatment; (2) Solder paste printing: Solder paste is evenly printed on the PCB pads. The quality of solder paste printing has an important impact on the soldering effect, and the amount of solder paste and the printing accuracy need to be controlled; (3) BGA chip placement: The BGA chip is accurately placed on the PCB pads with printed solder paste. The chip placement requires the use of high-precision chip placement equipment to ensure that the chip is aligned with the pads; (4) Reflow soldering stage: The PCB is placed in the reflow oven and heated according to the set temperature curve. The reflow soldering temperature curve generally includes a preheating zone, a heat preservation zone, a reflow zone, and a cooling zone; (5) Inspection and rework: After soldering is completed, the quality of the solder joints needs to be inspected. Online inspection equipment, such as automated optical inspection (AOI) and X-ray inspection, can be used to check for defects such as cold solder joints and bridging. For defective solder joints, rework and repair are required, typically using a BGA rework station for resoldering. The steps of vapor phase reflow soldering include: (1) Cleaning and pretreatment: Similar to reflow soldering, the pads of the PCB and BGA chip need to be cleaned and pretreated; (2) Flux coating: Flux is applied to the PCB pads to improve the wettability and soldering quality of the solder; (3) BGA chip placement: The BGA chip is placed on the PCB pads coated with flux; (4) Vapor phase reflow soldering stage: The PCB is placed in the vapor phase reflow soldering equipment. The heat transfer medium in the equipment generates steam after heating. The steam rises and contacts the PCB surface, melting the solder paste and realizing the soldering of BGA solder ball A1 to the PCB pads. The temperature control of vapor phase reflow soldering is more uniform than that of reflow soldering, which can effectively reduce soldering defects; (5) Cooling and inspection: After the soldering is completed, the solder joints are cooled naturally or solidified by a cooling device. Then the solder joint quality is inspected, and unqualified solder joints are reworked. The steps of the laser reflow soldering process include: (1) Cleaning and pretreatment: Cleaning the pads of the PCB and BGA chip to remove oxide layers and contaminants; (2) Flux coating: Applying flux to the PCB pads; (3) BGA chip placement: Placing the BGA chip on the PCB pads; (4) Laser reflow soldering stage: Using a high-energy laser beam to irradiate the solder joints, melting the solder and wetting the pads and solder balls A1 to form a reliable solder connection. Laser reflow soldering has the advantages of fast heating speed, concentrated energy, and small thermal impact on surrounding components, and is suitable for high-density packaging and small-sized component soldering; (5) Cooling and inspection: After soldering, the solder joints are cooled naturally or rapidly cooled by a cooling device. Finally, the solder joint quality is inspected to ensure the soldering quality. The steps of manual soldering include: (1) Cleaning and pretreatment: Clean the PCB and BGA chip pads with appropriate cleaning tools and solvents to remove oxides and dirt; (2) Flux application: Apply flux to the PCB pads; (3) BGA chip placement: Place the BGA chip on the PCB and use a high-precision positioning tool to ensure the chip is aligned with the pads; (4) Manual soldering: Heat the solder joints with a hot air gun or other heating tools to melt the solder and wet the pads and solder balls A1. The heating temperature and time need to be controlled to avoid damaging the components and PCB; (5) Inspection and rework: After soldering, inspect the solder joints with tools such as magnifying glasses and microscopes. For any defects found, perform manual rework repairs, such as using a desoldering pump to remove excess solder or reheating the solder joints for adjustment; The steps of the ball-mounting process include: (1) Pad cleaning: Clean the pads of the BGA chip to ensure that their surfaces are free of oxides and contaminants; (2) Applying flux: Apply flux to the pads to improve the wettability and adhesion of the solder; (3) Placing solder balls: Place solder balls A1 precisely on the pads coated with flux; (4) Reflow soldering: Place the BGA chip with solder balls A1 in a reflow oven and solder according to the set temperature profile to form a metallurgical bond between solder balls A1 and the pads; (5) Solder joint inspection: After soldering, inspect the solder joints to ensure that the soldering quality meets the requirements. For unqualified solder joints, rework and repair are performed.

[0094] In the simulation experiment, when the area of ​​the cross-section A1a of the spherical solder ball and the area of ​​the cross-section A1a of the solder ball A1 in the embodiment of this application are equal, the same force is applied to the spherical solder ball and the solder ball A1 in the embodiment of this application. Among them, the cross-section A1a of the solder ball A1 in the embodiment of this application has the longest length along the force direction 40 of the solder ball A1. The simulation results show that the maximum stress generated by the spherical solder ball is 0.0026098 MPa, while the maximum stress generated by the solder ball A1 in the embodiment of this application is 0.0020442 MPa. It can be seen that the maximum stress generated by the solder ball A1 in the embodiment of this application is smaller than that generated by the spherical solder ball. Compared with the spherical solder ball in the related art, the solder ball A1 in the embodiment of this application can reduce the maximum stress generated by the solder ball A1 under force, thereby having better adaptability to forces in a specific direction, better resistance to unevenly distributed forces, reducing the possibility of breakage due to excessive stress generated by the spherical solder ball, and improving the success rate of ball grid array packaging of chips.

[0095] Figure 6This is a schematic diagram of the simulation results of solder ball A1 in the embodiments of this application. The stress generated at point A1b of solder ball A1 is the largest, and the stress at point A1b is 0.0026098 MPa; the stress generated at point A1c of solder ball A1 is the smallest, and the stress at point A1c is 0.00016047 MPa.

[0096] In some embodiments, the simulation results are shown in the following table (Table 1):

[0097] Table 1 In the simulation experiment, the same force was applied to the four sizes of solder balls A1 in this application embodiment and the spherical solder balls in related technologies. The first type of solder ball A1 in this application embodiment had a force 'a' equal to 2R, resulting in the largest stress along its long axis, which was 0.0020 MPa. The second type of solder ball A1 in this application embodiment had a force 'a' equal to 1.5R, also resulting in the largest stress along its long axis, which was 0.0020 MPa. The third type of solder ball A1 in this application embodiment had a force 'a' equal to... R generates the maximum stress along the long axis, which is 0.0022 MPa; in the fourth type of solder ball A1 in this application embodiment, a is equal to 0.75R, generating the maximum stress along the long axis, which is 0.0024 MPa; the maximum stress generated by the spherical solder ball in the related art is 0.0025 MPa; where the long axis is the straight line direction of solder ball A1 passing through the midpoint 111 of the first side 11 and the midpoint 121 of the second side 12, and the force direction of solder ball A1 is 40, which is the long axis direction.

[0098] Therefore, it can be seen that the maximum stress generated by the four sizes of solder balls A1 in this application embodiment is less than the maximum stress generated by spherical solder balls in related technologies. This indicates that the solder balls A1 in this application embodiment effectively enhance the stress bearing capacity of the overall structure. Furthermore, a is inversely proportional to the stress along the long axis. That is, by increasing a, the adaptability of solder balls A1 to forces in a specific direction can be improved, reducing the possibility of excessive stress and damage caused by spherical solder balls, and improving the success rate of ball grid array packaging of chips.

[0099] In summary, in this embodiment, the cross-section A1a of the solder ball A1 includes a rectangular region 10, a first semicircular region 20, and a second semicircular region 30. The first side 11 of the rectangular region 10 is connected to the straight side of the first semicircular region 20, and the second side 12 of the rectangular region 10 is connected to the straight side of the second semicircular region 30. Since the cross-section A1a is parallel to the pad and the length of the cross-section A1a along the force direction 40 of the solder ball A1 is greater than the length of the cross-section A1a along other directions other than the force direction 40 of the solder ball A1, that is, the length of the cross-section A1a of the solder ball A1 is the longest in the force direction 40 of the solder ball A1, compared with the isotropic material mechanical properties of spherical solder balls in related technologies, the maximum stress generated by the solder ball A1 under force can be reduced, thereby improving the adaptability to force in a specific direction, reducing the possibility of excessive stress and breakage of the spherical solder ball, and improving the success rate of ball grid array packaging of chips.

[0100] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0101] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A solder ball (A1), characterized in that, The cross-section (A1a) of the solder ball (A1) includes a rectangular region (10), a first semicircular region (20), and a second semicircular region (30), and the cross-section (A1a) is parallel to the solder pad; The first side (11) of the rectangular region (10) is connected to the straight side of the first semicircular region (20), and the second side (12) of the rectangular region (10) is connected to the straight side of the second semicircular region (30). Wherein, the length of the cross section (A1a) along the force direction (40) of the solder ball (A1) is greater than the length of the cross section (A1a) in other directions besides the force direction (40) of the solder ball (A1).

2. The solder ball (A1) according to claim 1, characterized in that, The first side (11) and the second side (12) are arranged opposite each other, and the third side (13) and the fourth side (14) of the rectangular area (10) are arranged opposite each other; The lengths of the third side (13) and the fourth side (14) are both less than or equal to a preset threshold. The preset threshold is the product of the diameter of the first semicircular region (20) and the first preset value or the product of the diameter of the second semicircular region (30) and the first preset value.

3. The solder ball (A1) according to claim 2, characterized in that, The length of the third side (13) ranges from 0.25 mm to 0.5 mm; The length of the fourth side (14) ranges from 0.25 mm to 0.5 mm.

4. The solder ball (A1) according to claim 1, characterized in that, The first side (11) completely coincides with the straight side of the first semicircular region (20), and / or: The second side (12) completely coincides with the straight side of the second semicircular region (30).

5. The solder ball (A1) according to claim 1, characterized in that, The first semicircular region (20) and the second semicircular region (30) have the same shape and size.

6. The solder ball (A1) according to claim 1, characterized in that, The direction of the line connecting the midpoint (111) of the first side (11) and the midpoint (121) of the second side (12) is the same as the direction of the force (40).

7. The solder ball (A1) according to any one of claims 1 to 6, characterized in that, The area of ​​the cross section (A1a) ranges from 0.35 square millimeters to 0.5 square millimeters.

8. The solder ball (A1) according to any one of claims 1 to 6, characterized in that, The radius of the first semicircular region (20) ranges from 0.2 mm to 0.3 mm, and / or: The radius of the second semicircular region (30) ranges from 0.2 mm to 0.3 mm.

9. The solder ball (A1) according to any one of claims 1 to 6, characterized in that, The thickness of the solder ball (A1) ranges from 0.55 mm to 0.65 mm.

10. A ball grid array, characterized in that, The array includes a plurality of solder balls (A1) as described in any one of claims 1 to 9, wherein the solder balls (A1) in the ball grid array are arranged in an array.

11. The ball grid array according to claim 10, characterized in that, The square root of the ratio of the area of ​​the cross section (A1a) to π is less than or equal to the product of the center distance between adjacent solder balls (A1) and a second preset value.

12. A chip, characterized in that, It includes solder balls (A1) as described in any one of claims 1 to 9, or ball grid arrays as described in claims 10 or 11.

13. A solder pad, characterized in that, The shape of the pad is similar to the shape of the cross section (A1a), and the pad is used for soldering to the solder ball (A1) as described in any one of claims 1 to 9.

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