Reworked solder assembly without removing components

Abstract

A method for forming an electronic device includes: soldering a pin from a component (50) on a first side F1 of the board to a plated via of the board; and applying a solder paste to an opening of the plated through hole on a second side F2 of the plate, the second side of the plate being opposite the first side of the plate on which the component is positioned. The method may also include drawing a solder paste onto the pins to provide a reprocessed solder bond (80) that bonds at least one of the pins to the plated via.

Description

Technical Field

[0001] The present invention relates to solder joints between connectors and electrical devices, and more particularly to reworking solder joints. Background Art

[0002] Reflow soldering using a long industrial convection oven is a method of soldering surface mount technology components or surface mount technology (SMT) to a printed circuit board or PCB. Each section of the oven has a regulated temperature according to the specific thermal requirements of each assembly. By filling the vias with solder paste and inserting the component leads through the solder paste, a reflow oven dedicated to soldering surface mount components can also be used for through-hole components. However, wave soldering is a common method of soldering multi-lead through-hole components to a circuit board designed for surface mount components.

[0003] When used on a board containing a mixture of SMT and plated through-hole (PTH) components, through-hole reflow, when obtainable through a specially modified solder stencil, can allow the elimination of the wave soldering step from the assembly process, potentially reducing the assembly cost. The reflow soldering of through-hole components using solder paste in a convection oven process is referred to as invasive soldering. Summary of the Invention

[0004] In one embodiment, a method for forming an electronic device is provided, the method comprising solder bonding a pin from a component to a plated through-hole (PTH) of a board, wherein the component is located on a first side of the board. The method further comprises applying solder paste to an opening of the plated through-hole on a second side of the board, the second side of the board being opposite the first side of the board on which the component is positioned. The method may further comprise wicking the solder paste to the pin to provide a reworked solder bond that bonds at least one of the pins to the plated through-hole.

[0005] In another embodiment, a method for forming an electrical device is provided, the method comprising: solder bonding pins from a component to plated through-holes of a board, wherein the component is positioned on a first side of the board; and applying solder paste to an opening of the plated through-holes on a second side of the board, the second side of the board being opposite the first side of the board on which the component is positioned. The method may further comprise melting the solder paste; and wicking the solder paste to the pins by gravity to provide a reworked solder bond that bonds at least one of the pins to the plated through-holes.

[0006] In yet another embodiment, a method for forming an electronic device is provided, the method comprising: soldering pins of a component to a plated through hole of a board, the component being located on a first side of the board; and applying solder paste to an opening of the plated through hole on a second side of the board, the second side of the board being opposite to the first side of the board on which the component is positioned. The method may further comprise melting the solder paste; and drawing the solder paste to the pins with a vacuum to provide a reworked solder joint that bonds at least one of the pins to the plated through hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following detailed description will be best understood when read in conjunction with the accompanying drawings, which are given by way of example only and are not intended to limit the present disclosure thereto, wherein like reference numerals represent like elements and components, and wherein:

[0008] Figure 1 FIG. 9 is a side cross-sectional view showing soldering a component to a board by intrusive soldering pins to a plated through hole (PTH) according to an embodiment of the present invention, wherein one of the pins is open, or the solder between the pins of the component and the plated through hole (PTH) is insufficient to provide a reliable connection.

[0009] Figure 2 FIG. 13 is a side cross-sectional view showing accommodating a component in a support reinforcement such that an end of the plated through hole opposite to the side closest to the bonded component faces upward according to an embodiment of the present disclosure.

[0010] Figure 3 FIG. 17 is a side cross-sectional view showing installing a template exposing an opening to a plated through hole (PTH) according to an embodiment of the present disclosure.

[0011] Figure 4 FIG. 21 is a side cross-sectional view illustrating applying solder paste to a plated through hole passing through a template according to an embodiment of the present disclosure.

[0012] Figure 5 FIG. 25 shows removing the template from the structure depicted in Figure 4 FIG. 27 is a side cross-sectional view of removing the template from the structure depicted in FIG. 25.

[0013] Figure 6 FIG. 31 is a side cross-sectional view showing a component with intrusive solder connected to a PCB positioned in a hot air ball grid array (BGA) rework station according to an embodiment of the present invention, having Figure 5 the second application of solder paste shown in FIG. 33.

[0014] Figure 7 FIG. 37 is a side cross-sectional view of a reflow process applied to the structure shown in Figure 6 FIG. 39, wherein gravity causes Figure 5The second application of solder shown is drawn deeper into the plated through hole (PTH).

[0015] Figure 8 is a side cross-sectional view showing the assembly of a reworked solder joint after cooling and removal from the Figure 7 hot air balloon grid array (BGA) rework station depicted in

[0016] Figure 9 is a side cross-sectional view according to another embodiment of the present invention, where after the application in Figure 5 and the removal of the stencil depicted in Figure 6 vacuum is used in combination with gravity to rework the solder.

[0017] Figure 10 is a side cross-sectional view of a reflow process applied to the structure shown in Figure 9 where the application of gravity in combination with vacuum draws the Figure 5 second application of solder shown deeper into the plated through hole (PTH).

[0018] Figure 11 is a side cross-sectional view showing the assembly of a reworked solder joint after cooling and removal from the Figure 10 hot air balloon grid array (BGA) rework station depicted in Detailed Description

[0019] Detailed embodiments of the claimed structures and methods are disclosed herein; however, it should be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods that may be implemented in various forms. Additionally, each example given in connection with the various embodiments is intended to be illustrative, not restrictive. Further, the figures are not necessarily drawn to scale, and some features may be enlarged to show details of particular components. Accordingly, the specific structural and functional details disclosed herein should not be construed as restrictive, but merely as a representative basis for teaching one skilled in the art to employ the methods and structures of the present disclosure in various manners. For the purposes of the following description, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom" and their derivatives shall refer to embodiments of the present disclosure as oriented in the figures. The term "located on" means that a first element (e.g., a first structure) is present on a second element (e.g., a second structure), where an intermediate element (e.g., an interfacial structure, e.g., an interfacial layer) may be present between the first element and the second element. The term "in direct contact" means that a first element (e.g., a first structure) and a second element (e.g., a second structure) are joined without any intermediate conductive, insulating, or semiconductor layer at the interface of the two elements.

[0020] The methods and structures described herein provide for reworking intrusive solder assemblies without removing components. Intrusive soldering is increasingly being used for a number of positive reasons. For example, intrusive soldering can be applied to solder application where there is an increase in the physical thickness of the original card. Additionally, intrusive soldering can provide an effective connection to the pin lengths of plated through hole (PTH) components.

[0021] Furthermore, wave soldering is a traditional type of operation that is not cost-effective and, for a number of reasons, the industry generally desires to move away from this technology. For example, in some cases, the pins used for solder connections are shorter than the thickness of the card. In some cases, when used in cards with a larger thickness, the shortness of the component pins means that these components cannot be soldered adequately and reliably using methods such as wave soldering or solder pot soldering.

[0022] Intrusive soldering provides a solution to some aspects of the above deficiencies. "Intrusive soldering" is a process in which a stencil or syringe is used to apply solder paste for through hole components to accommodate through hole components that are inserted and reflow soldered with surface mount components.

[0023] As mentioned above in the term "reflow soldered together", "reflow soldering" is a process in which a solder paste (a viscous mixture of powdered solder and flux) is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to heating, such as controlled heating. In response to the application of heat, the solder paste refluxes in a molten state, thereby creating a permanent solder joint. The heating can be accomplished by passing the assembly through a reflow oven, under an infrared lamp, or (unconventionally) by soldering individual joints with a desoldering hot air pen.

[0024] However, it has been determined that, like all soldering methods, intrusive soldering also has some deficiencies that may require reworking. A common scenario that results in defects in solder joints formed using intrusive soldering is that, due to the smaller size of the plated through hole (PTH) components, the volume of solder in the pin holes may be insufficient, which may result in the solder joint having insufficient solder for reliable contact. In some cases, a complete "open" may occur if the operation does not inject into the holes for contact. Other defects may be due to poor wetting of the solder to the pins or the plated through hole (PTH) components.

[0025] When these defects occur, a record process that can correct the above defects is a rework process of removing components from the connection. In one example, the rework process may include placing the connector / printed circuit board (PCB) in a ball grid array (BGA) hot air rework system, where the fitting can be subjected to a global preheat typically up to about 120 °C. In some instances, the hot air rework nozzle is positioned over the pin in hole component and lowered above the pin in hole component. Local hot nitrogen is applied until the solder in the plated through hole melts, and then the operator pulls out the component with pliers. This is how the component is removed from the connection, and this type of prying can damage the component adversely. In some examples, then a solder sucker can be used to remove the solder from the plated through hole. Then, the card can be cooled, and then new solder paste can be applied to the plated through hole (PTH). In some examples, a new component can be placed into the plated through hole (PTH), pushing the paste down into the hole. Thereafter, the fitting can be returned to the BGA hot air rework system. The reflow for providing a new connection may include similar steps of preheating and local heating around the component system using the nozzle. The above process is labor-intensive, may damage the components involved and is time-consuming.

[0026] The methods described herein provide a rework process that can be performed on an intrusive solder component without removing and / or replacing the components soldered to the board / card. More specifically, the methods described herein can use a combination of repackaged solder paste and gravity and / or vacuum techniques to perform the rework steps for rework. Now refer Figures 1-11 to describe the methods and structures of the present disclosure in more detail.

[0027] Figure 1 An embodiment of a component 50 is shown, which is soldered (by solder shown by reference numeral 30) to a board 55 by soldering the pins 40 in an intrusive manner to the plated through hole (PTH) 25. In Figure 1 the embodiment shown, one of the pins 40a is open, or there is not enough solder between the pin 40a of the component 50 and the plated through hole (PTH) 25 to provide a reliable connection.

[0028] In one embodiment, component 50 may be an integrated circuit (IC) chip 5 solder-bonded to a board 55, such as a printed circuit board (PCB). An integrated circuit or monolithic integrated circuit (also referred to as an IC, chip, or microchip) is a set of electronic circuits on a small flat piece of semiconductor material (or "chip"). The semiconductor material may be a Group-IV semiconductor, such as silicon (Si), or may be a Group-III-V semiconductor material, such as gallium arsenide (GaAs). A large number of field effect transistors (FETs), such as MOSFETs (metal-oxide-semiconductor field effect transistors), may be integrated into the chip. The type of semiconductor device, such as an FET, may include horizontally oriented devices, vertically oriented devices, fin field effect transistors, nanowires, and / or nanosheet channel-type devices. Any field effect transistor (FET), such as including a gate structure with a channel separating source and drain regions, may be integrated into the chip. The above examples of FET types are provided for illustrative purposes only and are not intended to be limiting. Note that regardless of the type of device provided by the component, the electrical connection to component 50 is through pins 40, 40a. Pins 40, 40a are made of a conductive material, such as a metal, such as copper, having dimensions and geometries for bonding to the plated through holes (PTHs) of board 55.

[0029] In some embodiments, board 55 may be a printed circuit board. A printed circuit board (PCB) includes electrical contact pads and paths to carry electrical signals to components 50 bonded thereto. The printed circuit board (PCB) may be a metal core printed circuit board (MCPB). In some embodiments, other materials, such as FR4, may also be used. As described, pins 40, 40a of component 50 are solder-bonded to the plated through holes (PTHs) 25 of board 55 to provide an electrical connection between board 55 and component 50.

[0030] A "plated through hole" is a feature milled or drilled through the body of board 55 and then plated with a conductive material. For example, the through hole may be plated with conductive copper (Cu). Electrical connections to other components on the board are made by extending traces between the plated through holes (PTHs) 25 and then soldering components, such as the element identified by reference numeral 50, at these locations.

[0031] As described above, the solder connection (solder denoted by reference numeral 30) between pins 40, 40a of component 50 and the plated through hole (PTH) can be provided by invasive soldering. "Invasive soldering" is a process in which a stencil or syringe is used to apply solder paste for through-hole components to accommodate through-hole components inserted and reflow soldered with surface-mounted components. As used herein, the term "solder" refers to any metal or metal compound or alloy that is melted and then allowed to cool to join two or more metal surfaces together. The solder joint 30 can be composed of a metal suitable for soldering. For example, in some embodiments, the solder 30 can be composed of a eutectic alloy of tin and lead or a lead-free solder composition. In some examples, the solder 30 can be a tin / copper / nickel-based solder, such as Sn-0.7Cu. In another example, the solder 30 can be a lead / tin / silver-based solder, such as Pb93-Sn5-Ag2. In yet another example, the solder 30 can be a tin / silver-based solder, such as Sn-3.5Ag. In a further example, the solder 30 can be a tin / silver / copper-based solder, such as Sn-3.8Ag-0.7Cu. In yet another example, the solder 30 can be a lead / tin-based solder, such as Pb980-10Sn. Generally, the melting temperature of the solder is in the range of 150°C to 300°C.

[0032] In Figure 1 the illustrated embodiment, one of the pins 40a is open, or there is not enough solder between the pin 40a of component 50 and the plated through hole (PTH) 25 to provide a reliable connection. This situation can be visually observed, or electrical testing can determine the presence of the open pin.

[0033] Figure 2 An embodiment is shown in which the component is received in a support reinforcement 60 such that the end face of the plated through hole 25 opposite the side closest to the mating component 50 faces upward. The side of the plated through hole 25 close to the mating element 50 is referred to as being on the front face F1 of the board 55. The side of the plated through hole 25 opposite the front face F1 of the board 55 is referred to as the back face F2 of the board 55. As Figure 1 and 2 shown, the solder 30 applied initially by invasive soldering is closer to the front face F1 of the board 55, opposite the back face F2 of the board 55. However, after soldering the component 50 to the plated through hole 25, the opening for the pins 40, 40a to engage at the front face F1 of the board 55 is blocked. Figure 2 An embodiment is shown in which the solder joining fittings of the component 50 and the board 55 are positioned in a support reinforcement 60 that mechanically supports the component, and the back face F2 of the board 55 is positioned such that additional application of solder can be introduced into the plated through hole 25 from the back face F2 of the board 55.

[0034] Figure 3An embodiment is shown of a stencil 63 that exposes openings to plated through-holes (PTHs) 25. Applying the stencil 63 is a step of applying solder paste 64 from the back side F2 of the board 55 to pins (e.g., including opening pins 40a), with the component being received in the support reinforcement 60. The stencil 63 can be a structure having holes therethrough to direct the solder paste passing through the stencil 63 at least to the opening pins 40a. In some cases, the stencil 63 can have openings corresponding to all of the plated through-holes 25 that are to be joined to the pins 40, 40a of the component soldered to the board 55. The stencil 63 is made of a solid material that blocks the passage of the solder paste 65 through the stencil 63, except for the openings corresponding to the intended local application of the solder paste 65. In some examples, the stencil 63 can be a metal plate. In some examples, the stencil 63 can also include tape. For example, the stencil 63 can include a silicone tape having a polyamide substrate. In some embodiments, the stencil 63 can include a combination of a patterned metal plate and tape, the patterned metal plate having openings corresponding to the plated through-holes 25. In some embodiments, the stencil 63 can be made entirely of tape. In yet another embodiment, instead of using the stencil 63, a syringe can be used to apply the solder paste 65 to the plated through-holes 25.

[0035] Figure 4 Shown is the application of the solder paste 65 to the plated through-holes 25 passing through the stencil 63. The solder paste 65 can first be deposited on the stencil 63, for example, by a brush, syringe, ejector, curtain flow, etc., and then the solder paste 65 can be spread and forced through the openings of the stencil 63 using a squeegee 66. A "squeegee" is a tool having a flat, smooth deformable blade, such as rubber, plastic, and / or metal, which is used to remove or control the flow of material on a substantially flat surface, such as the stencil 63 (when present).

[0036] "Solder paste" is made of a combination of solder powder pre-blended to form a paste and a thick flux. This combination results in a thick material that allows for easier deposition, typically by stencil printing or deposition. In solder reflow applications, the solder paste is heated to a temperature above the liquidus temperature. At this temperature, the flux is activated and will remove oxides from the surfaces of the leads, metal pads, and solder powder, allowing the solder powder to effectively melt and form a solid metal joint.

[0037] The alloy type and particle size of the solder powder in the solder paste 65 determine the time above the liquidus, the oxide level, the strength of the intermetallic bond, the minimum aperture size, and the inner diameter for dispensing printing. The flux used for the solder paste 65 can be made of a combination of ingredients such as rosin, activators, rheological additives, and solvents. The combination of these components determines the subclass of flux in which it falls, which determines the rheological properties of the material and how the flux removes oxides.

[0038] In some embodiments, the alloy composition of the solder paste 65 can be composed of various alloys, such as a combination of eutectic (tin and lead) and lead-free, typically SAC305 (tin, 3.0 silver, 0.5 copper). Alloys mainly composed of tin (Sn) have a low melting point and high tensile and shear strength. Other metals can also be added to further modify the mechanical properties of the alloy. For example, lead can reduce the total melting temperature and form strong connections with other metals such as copper and aluminum, which are commonly used for PCB pads or component leads. Lead-free solder alternatives are attractive, such as SAC305, which consists of tin, silver, and copper. Copper reduces the melting point of the alloy and helps the molten solder to wet, while silver increases the mechanical strength but has lower ductility than lead. Additionally, there can be other alloys with combinations of different metals and percentage levels to improve the quality of the solder joint. Some of these metals include, but are not limited to, antimony, bismuth, indium, and nickel.

[0039] The flux of the solder paste is a metallurgical material that has multiple functions and is a component in metal joining and extraction metallurgy. The flux provides functions as a stabilizer, a fluidizer, and / or a chemical cleaner. In solder paste, one purpose of the flux is to act as a cleaner. The flux is a reducing agent that prepares the metal surface by removing oxides, debris, and dirt. This prepares the surface by preventing oxidation on the metal surface and the joining material and helps the wetting of the molten metal. The flux of the solder paste 65 can be one of a water-soluble flux, a no-clean flux, and a traditional rosin flux.

[0040] After the solder paste 65 is applied, the solder paste 65 is forced through the holes in the stencil 63 by the squeegee 66. In Figure 4 the illustrated embodiment, the solder paste 65 is pushed through the openings in the stencil 63 into the openings of the plated through-holes 25. At this stage of the process flow, the solder paste 65 is present near the back surface F2 of the board 55 and is not in direct contact with the pins 40, 40a.

[0041] Note that some embodiments have been considered where the solder paste 65 is directly applied to the openings of the plated through-holes 25 using a syringe. In this example, the stencil 65 and the squeegee 66 can be omitted.

[0042] Figure 5 It shows removing the stencil 63 from the Figure 4 illustrated structure. In some embodiments, the excess solder can be removed before or during the removal of the stencil 63.

[0043] Figure 6Shows an embodiment of an invasive solder connection assembly 50 to a board 55 (such as a printed circuit board (PCB)) located within a hot gas ball grid array (BGA) rework station 70, with a second application of solder paste 65. The BGA rework station 70 is a machine that can be used to recoat or repair printed circuit boards (PCBs) with ball grid array (BGA) packages and surface mount devices (SMDs). These reworks allow technicians to remove defective parts, reinstall incorrectly placed parts, or replace any missing parts in the PCB. Typically, the BGA rework station works by forcing heated gas 76 through a nozzle that is lowered close to the board 55. Additionally, in Figure 6 the illustrated embodiment, the BGA rework station 70 includes a backside heating element 75 that can work in conjunction with the heated gas 76 to increase the temperature of the solder 30, 65.

[0044] For the method of the present disclosure, the fitting of the board 55 and the assembly 50 with the second application of solder paste 65 to the plated through holes 25 is placed in the hot air BGA rework machine 70 such that the board 55 (such as a PCB) is inverted, with the invasive assembly 55 facing down and the exposed openings of the plated through holes (PTHs) facing up. More particularly, the backside F2 of the board 55 faces up.

[0045] Still referring to Figure 6 , to repair the open pin 40a, the hot air nozzle of the hot air BGA rework machine 70 is aligned with the position of the plated through hole (PTH) 25 that needs to be repaired. Then hot air rework is applied. For example, nitrogen can be used to improve wettability, and the temperature of the hot air rework can be sufficient to melt the solder but not exceed 240 °C. In some embodiments, the temperature of the hot air rework can be in the range of 200 °C to 235 °C. The time period for the hot air rework is less than 10 minutes, such as seven minutes or less.

[0046] In some embodiments, aligning the hot air nozzle with the position of the plated through hole that needs to be repaired and performing the hot air rework process causes the reflow of the solder paste 65.

[0047] Figure 7 Describes an embodiment of a reflow process applied to the Figure 6 illustrated structure, where gravity pulls the solder of the solder paste 65 deeper into the plated through hole (PTH) 25 from the Figure 5 second application as shown. During reflow, the solder paste 60 melts, and gravity pulls the solder downward to the pins in the plated through hole 25 to contact the pins 40, 40a. The solder flowing to the pins forms a reworked solder joint 80 that electrically connects the pins 40, 40a to the plated components of the plated through hole (PTH).

[0048] Figure 8shows Figure 7 the fitting of the reworked solder joint 80 after the hot gas ball grid array (BGA) rework station 70 shown in Figure 7 has been cooled and removed. After reflow, once the fitting has cooled, X-ray positioning is used to verify whether solder opening defects (such as pin 40a) have been repaired. More particularly, in some embodiments, the reworked solder joint 80 provides direct contact of the solder paste 65 between the plated sidewalls of the plated through-hole 25 and the pin 40a.

[0049] It should be noted that Figures 1 to 8 the embodiment depicted in Figures 1 to 8 represents only one embodiment of the present invention. It should also be noted that the method described with reference to Figures 1 to 8 is not intended to be limited to the steps shown in the provided figures. For example, any number of preliminary, intermediate, and final process steps may also be within the scope of the present claims but are not shown in the provided figures. Additionally, Figures 1-8 Figures 1-8 shows another embodiment of the present invention, where a vacuum is also applied to the solder paste 65 during reflow to draw the solder into contact with the pins (e.g., open pin 40a). Figures 9-11 Figures 9-11 shows yet another embodiment of the present invention, where a vacuum is also applied to the solder paste 65 during reflow to draw the solder into contact with the pins (e.g., open pin 40a).

[0050] Figures 9-11 the embodiment described in Figures 9-11 may start with a structure resulting from the process flow described above with reference to Figures 9-11 . Figures 1-5 Figures 1-5 Figure 9 Figure 9 shows another embodiment of a hot gas ball grid array (BGA) rework station 70, which includes a top-side heating element 76 and a back-side heating element 75, as well as a vacuum port 82 through which a vacuum can be applied. Figure 9 Figure 9 shows that a vacuum, such as the vacuum applied through the vacuum port 82, is used in combination with gravity to rework the solder after applying the solder paste 65 shown in Figure 9 and removing the stencil 63 shown in Figure 9 . Figure 5 Figure 5 Figure 6 Figure 6 Figure 9 Figure 9 shows that the hot gas ball grid array (BGA) rework station 70 shown in Figure 9 is similar to the hot gas ball grid array (BGA) rework station 70 shown in Figure 9 , except that Figure 5 Figure 5 Figure 9 Figure 9 shows that the rework station 70 shown in Figure 9 includes additional heating elements and a port 82 for applying a vacuum, as well as a seal 81 for sealing the chamber in which the rework process is performed. The heating elements 75, 76 can operate to increase the temperature of the solder 30, 65 for reflow, while the vacuum applied through the vacuum port 82 is used to draw the molten solder into the depth of the plated through-hole 25 to bring the solder stream 65 into contact with the pins 40, 40a, such as with the open pin 40a.

[0051] For the method of the present disclosure, the board 55 and the component 50 assembly having the second application of solder paste 65 to the plated through hole 25 are placed in a hot air BGA rework machine 70 such that the board 55 (e.g., a PCB) is inverted, with the invasive component 55 facing down and the exposed opening of the plated through hole (PTH) facing up. More particularly, the rear side F2 of the board 55 faces up.

[0052] Still referring to Figure 9 , to repair the open pin 40a, the hot air nozzle of the hot air BGA rework machine 70 is aligned with the position of the plated through hole (PTH) 25 that needs to be repaired. Then hot air rework is applied. In some embodiments, the hot air rework may include aligning the top side IR heating element head 76 and the bottom side IR heating element head 75 with the position of the plated through hole 25 that needs to be repaired, e.g., the plated through hole 25 where there is an open pin 40a. Similar to the embodiments described with reference to Figures 1-8 , nitrogen can be used to improve wettability, and the temperature of the hot air rework can be sufficient to melt the solder but not exceed 240 °C. In some embodiments, the temperature of the hot air rework can be in the range of 200 °C to 235 °C. The time period for hot air rework is less than 10 minutes, e.g., seven minutes or less.

[0053] Figure 9 The illustrated embodiment also includes applying a vacuum for drawing the reflow solder of the solder paste 65 into direct contact with the pins 40, 40a of the component 50 present in the plated through hole 25. In some embodiments, applying a vacuum includes sealing the IR heating element heads 75, 76 to the board 55. Sealing the IR heating element heads 75, 76 to the board 55 (PCB board) may include the seal of reference numeral 81. After applying the seal 81, a vacuum can be applied. The seal 81, the IR heating element heads 75, 76, and the component of the board 55 define a space that can be used as a vacuum chamber. The vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump, e.g., applied through a vacuum port 82. This creates a low pressure environment inside the chamber, commonly referred to as a vacuum. For comparison purposes, atmospheric pressure is approximately 760 Torr. In some embodiments, the application of the vacuum applied through the vacuum port 82 creates a low vacuum ranging from 760 Torr to 25 Torr. In some embodiments, applying a vacuum through the vacuum port 82 creates a medium vacuum of 25 to 1×10 -3 Torr. In some embodiments, applying a vacuum creates a high vacuum (hard) of 1×10 -3 Torr to 1×10 -9 Torr. In some embodiments, applying a vacuum creates 1×10 -9 to 1×1×10 -12Ultra-high vacuum of the chuck. Note that the above-mentioned vacuum applied through the vacuum port 82 can draw the solder paste 60 from the opening at the back surface F2 of the board 50 toward the central portion of the plated through-hole 25.

[0054] During reflow, the solder paste 60 melts, and gravity and the vacuum pull the solder downward into the pins 40, 40a in the plated through-holes of the board 55. Figure 10 An embodiment of a high-temperature and vacuum-assisted reflow process applied to Figure 9 the structure shown is presented, where, in addition to gravity, the vacuum applied through the vacuum port 82 draws the solder of the solder paste 65 deeper into the plated through-hole (PTH) 25 during the Figure 5 second application shown. During reflow, the solder paste 65 melts, and gravity pulls the solder downward to the pins 40, 40a in the plated through-hole 25 to contact the pins 40, 40a. The solder flowing to the pins 40, 40a forms a reworked solder joint 80 that electrically connects the pins 40, 40a to the plated components of the plated through-hole (PTH).

[0055] Figure 11 An illustration is given of Figure 7 the fitting of the reworked solder joint 80 after the hot air balloon grid array (BGA) rework station 70 shown in

[0056] is cooled and removed. After reflow, once the fitting cools, the x-ray position is used to verify whether solder opening defects (such as the pin 40a) have been repaired.. More specifically, in some embodiments, the reworked solder joint 80 provides direct contact of the solder paste 65 between the plated sidewall of the plated through-hole 25 and the pin 40a. Figures 1-11 As shown, the rework of the solder joint shown in

[0057] allows the component 50 to remain joined to the board 55, such as a printed circuit board (PCB). More specifically, the solder joint 80 can be fabricated to correct the open pin 40a resulting from joining the component 50 to the board 55 by invasive soldering. The solder joint 80 is produced by a second application of the solder paste 65 to the back surface of the plated through-hole 25, where the joining of the solder paste 65 to the pins 40, 40a can be facilitated by elevated temperature, gravity, and / or vacuum.

[0058] This embodiment may include the design of an integrated circuit chip, which may be created in a graphical computer programming language and stored in a computer storage medium (such as a disk, magnetic tape, physical hard disk drive, or virtual hard disk drive in a storage area network). If the designer does not fabricate the chip or the lithography mask used to fabricate the chip, the designer may transfer the resulting design directly or indirectly to such an entity by physical means (e.g., by providing a copy of the storage medium storing the design) or electronically (e.g., via the Internet). The stored design is then converted into an appropriate format (e.g., GDSII) for fabricating the lithography mask, which typically includes multiple copies of the chip design in question to be formed on the wafer. The lithography mask is used to define the areas of the wafer (and / or the layers thereon) to be etched or otherwise processed.

[0059] The methods described herein can be used in the fabrication of integrated circuit chips. The resulting integrated circuit chips can be distributed in the form of a raw wafer (i.e., as a single wafer with multiple unpackaged chips), as bare chips, or in a packaged form. In the latter case, the chip is mounted in a single-chip package (e.g., a plastic carrier with leads fixed to a motherboard or other higher-level carrier) or a multi-chip package (e.g., a ceramic carrier with one or both of surface interconnects or buried interconnects). In any case, the chip is then integrated with other chips, discrete circuit elements, and / or other signal processing devices as part of (a) an intermediate product (such as a motherboard) or (b) a final product. The final product can be any product that includes an integrated circuit chip, ranging from toys and other low-end applications to high-end computer products with a display, keyboard, or other input devices and a central processing unit.

[0060] It should also be understood that material compounds will be described in terms of the listed elements, e.g., SiGe. These compounds include different proportions of elements within the compound, e.g., SiGe includes ix Ge 1-x , where x is less than or equal to 1, etc. Additionally, other elements may be included in the compound and still function in accordance with this principle. Compounds with additional elements will be referred to herein as alloys.

[0061] References in the specification to "one embodiment" or "an embodiment" and other variations thereof mean that the specific features, structures, characteristics, etc. described in connection with that embodiment are included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" and any other variations thereof throughout the specification do not necessarily all refer to the same embodiment.

[0062] It should be understood that in cases such as “A / B”, “A and / or B”, and “at least one of A and B”, the use of any of the following “ / ”, “and / or”, and “at least one of” is intended to cover the selection of only the first-listed option (A), or only the second-listed option (B), or the selection of both options (A and B). As a further example, in the cases of “A, B, and / or C” and “at least one of A, B, and C”, such wording is intended to include the selection of only the first-listed option (A), or only the second-listed option (B), or only the third-listed option (C), or the selection of only the first and second-listed options (A and B), or the selection of only the first and third-listed options (A and C), or the selection of only the second and third-listed options (B and C), or the selection of all three options (A and B and C). This can be extended to any number of items listed, which will be apparent to those of ordinary skill in the art and related fields.

[0063] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms “comprises”, “comprising”, “includes” and / or “including” when used herein specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0064] For ease of description, spatially relative terms such as “below”, “beneath”, “lower”, “above”, “upper” and the like may be used herein to describe the relationship of one element or feature to another element or feature, as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as “below” or “beneath” another element or feature would then be oriented “above” the other element or feature. Thus, the term “beneath” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein may be interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or there may be one or more intervening layers.

[0065] While methods and structures for reworking solder assemblies without removing components have been particularly shown and described with respect to their preferred embodiments, those skilled in the art will understand that the foregoing and other changes in form and detail may be made without departing from the scope of the present disclosure. Accordingly, the present disclosure is not limited to the exact forms and details described and shown, but falls within the scope of the appended claims.

Claims

1. A method for forming an electronic device, comprising: soldering pins from a component to a plated through-hole of a board, the component being located on a first side of the board; applying solder paste to an opening of the plated through-hole on a second side of the board, the second side of the board being opposite to the first side of the board on which the component is positioned; and drawing the solder paste to the pins to provide a reworked solder joint that joins at least one of the pins to the plated through-hole.

2. The method according to claim 1, wherein an invasive solder joint is used to join the solder joint from the pins of the component to the plated through-hole of the board.

3. The method according to claim 1, wherein, open pins that are not soldered to the opening of the plated through-hole of the board are created by the solder joint from the pins of the component to the plated through-hole of the board.

4. The method according to claim 3, wherein, the open pins are soldered by drawing the solder paste to the pins to provide the reworked solder joint.

5. The method according to claim 4, wherein the drawing of the solder paste includes reflowing the solder paste by heating the solder paste and using gravity to draw the solder paste to the pins.

6. The method according to claim 1, wherein the drawing of the solder paste includes applying a vacuum.

7. The method according to claim 1, wherein applying the solder paste comprises: applying a stencil to the second side of the board, the stencil having openings corresponding to the plated through-holes; and forcing the solder paste through the openings of the stencil.

8. The method according to claim 7, wherein the stencil includes at least one of a metal plate, a tape, or a combination thereof.

9. A method for forming an electrical device, comprising: soldering pins from a component to a plated through-hole of a board, the component being located on a first side of the board; applying solder paste to an opening of the plated through-hole on a second side of the board, the second side of the board being opposite to the first side of the board on which the component is positioned; melting the solder paste; and using gravity to draw the solder paste to the pins to provide a reworked solder joint that joins at least one of the pins to the plated through-hole.

10. The method according to claim 9, wherein, an invasive solder joint is used to join the solder joint of the pins from the component to the plated through-hole of the board.

11. The method according to claim 9, wherein, open pins that are not soldered to the opening of the plated through-hole of the board are created by the solder joint of the pins from the component to the plated through-hole of the board.

12. The method according to claim 11, wherein, the open pins are soldered by drawing the solder paste to the pins to provide the reworked solder joint.

13. The method according to claim 9, wherein applying the solder paste comprises: applying a stencil to the second side of the board, the stencil having openings corresponding to the plated through-holes; and forcing the solder paste through the openings of the stencil.

14. The method according to claim 13, wherein the template comprises at least one of a metal plate, a tape, or a combination thereof.

15. A method for forming an electronic device, comprising: soldering pins from a component to plated through-holes of a board, the component being located on a first side of the board; applying solder paste to an opening of the plated through-hole on a second side of the board, the second side of the board being opposite to the first side of the board on which the component is positioned; melting the solder paste; and drawing the solder paste to the pins by vacuum to provide a reworked solder joint that couples at least one of the pins to the plated through-hole.

16. The method according to claim 15, wherein, an invasive solder joint is used to couple the solder joint of the pins from the component to the plated through-hole of the board.

17. The method according to claim 15, wherein, open pins that are not soldered to the opening of the plated through-hole of the board are generated by the solder joint of the pins from the component to the plated through-hole of the board.

18. The method according to claim 15, wherein, the open pins are soldered by drawing the solder paste to the pins to provide the reworked solder joint.

19. The method according to claim 18, wherein applying the solder paste comprises: applying a template to the second side of the board, the template having openings corresponding to the plated through-holes; and forcing the solder paste through the openings of the template.

20. The method according to claim 19, wherein the template comprises at least one of a metal plate, a tape, or a combination thereof.

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