System and method for disassembling a double-sided printed circuit board assembly

Abstract

A system for removing defective BGA chips from a double-sided PCBA having a securing section and a cooling section. The securing section includes at least one shield that prevents hot air from a hot air gun from heating BGA chips adjacent to the defective BGA chip. The cooling section prevents overheating of BGA chips on the opposite side of the double-sided PCBA by conducting heat away from the BGA chips during handling.

Description

Technical Field

[0001] The field of the invention is electronic chip manufacturing. Background Art

[0002] The Background Description includes information that may be useful in understanding the present invention. No admission is made that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication explicitly or implicitly referenced is prior art.

[0003] Extracting chips, such as ball grid array (BGA) chips, from printed circuit board assemblies (PCBAs) by heating them with a hot air gun is a common method for replacing defective chips. However, this method can cause collateral thermal damage to adjacent components, especially heat-sensitive components (e.g., DRAM components). The risk of collateral thermal damage can also be higher on PCBAs with high component density and / or double-sided PCBAs with symmetrically placed chips.

[0004] There are several existing solutions to minimize the collateral thermal damage caused during chip extraction (as follows):

[0005] a) using a coolant (e.g., a stream of cold air) to cool adjacent components while heating;

[0006] b) Redesign of the BGA rework fixture (with a specially shaped heat gun nozzle and a shield with fine apertures placed over the BGA chip that needs to be extracted);

[0007] c) Isolating the reworked BGA chip, which allows hot air to flow directly over the surface of the reworked BGA chip to protect adjacent components; and

[0008] d) Shield adjacent components with heat-resistant materials.

[0009] However, the following limitations are observed that are not applicable to applications involving extraction of chips from a double-sided PCBA, especially for PCBAs with symmetrical BGA chips placed on both sides.

[0010] These restrictions are:

[0011] a) Inadequate consideration of potential collateral thermal damage to adjacent dies located on the opposite side of the reworked die;

[0012] b) Failure to consider potential thermal damage to the chip opposite the reworked chip due to heat conduction from the reworked chip to the opposite chip via the solder joints and the PCB, especially for PCBA designs with symmetrically placed BGA chips on both sides;

[0013] c) Failure to consider potential collateral thermal damage to high-density SMT PCBAs, small-size PCBAs, and double-sided PCBAs with BGA chips placed symmetrically on both sides;

[0014] Therefore, a need remains for a system that effectively and easily removes defective BGA chips from a double-sided PCBA while also protecting other BGA chips on both sides of the PCBA from damage caused by the heating process. Summary of the Invention

[0015] The present subject matter provides an apparatus, system, and method for removing defective BGA chips from a double-sided PCBA. The system includes a holder or holding area configured to hold a PCBA inserted into the system, a hot air gun, and at least one heat-resistant shield. The holder or holding area is configured to hold a PCBA inserted into the system; the hot air gun is positioned to align with a defective BGA chip on a first side of the PCBA when the PCBA is installed in the system; and the at least one heat-resistant shield is movable via a track so that the heat-resistant shield can be moved into position to protect adjacent BGA chips on the first side of the PCBA from heat emitted by the hot air gun.

[0016] The system also includes a cooling section having a cooling source that supplies cooling air toward the PCBA via a heat pipe. The heat pipe may be covered with a heat-resistant coating or cladding material along its length, leaving the end of the pipe exposed or uncovered to contact the BGA chip on the second side of the PCBA, opposite the defective chip. The cooling section also includes at least one heat dissipation element (e.g., a heat sink) located on one side of the heat pipe. This side of the heat pipe contacts the adjacent BGA chip on the second side of the PCBA via a heat dissipation medium (e.g., thermally conductive adhesive) on the surface of the at least one heat dissipation element.

[0017] Various objects, features, aspects, and advantages of the present subject matter will become more apparent from the following detailed description of preferred embodiments and the accompanying drawings, in which like reference numerals represent like components.

[0018] All publications cited herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. To the extent that a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0019] The following description includes information that may be useful in understanding the present invention. No admission is made that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication explicitly or implicitly referenced is prior art.

[0020] In certain embodiments, the numerals for describing and claiming the amount of the representation composition of a particular embodiment of the present invention, characteristic (such as concentration), reaction conditions, etc. should be understood to be modified by the term "about" in some cases. Therefore, in certain embodiments, the numerical parameters set forth in written description and the appended claims are approximate values, which can change according to the desired characteristics sought to be obtained in a particular embodiment. In certain embodiments, this numerical parameter should be interpreted according to the number of reported significant figures and by applying common rounding techniques. Although the numerical range and the parameters of the wide range of some embodiments of the present invention are approximate values, the numerical value set forth in a particular example is reported as accurately as possible. In certain embodiments of the present invention, the numerical value provided may contain some errors, and these errors are necessarily due to the standard deviation found in their respective test measurements causing.

[0021] Unless the context dictates otherwise, all ranges set forth herein should be interpreted as including their endpoints, and open ranges should be interpreted as including only commercially practical values. Similarly, unless the context dictates otherwise, all lists of values ​​should be interpreted as including intermediate values.

[0022] As used throughout the specification and claims herein, the meanings of "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Furthermore, as used throughout the specification herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0023] The range of values ​​listed here is only intended to be used as a shorthand method for individually referring to each individual value falling within the scope. Unless otherwise noted herein, each individual value is incorporated into this specification as if it were individually listed herein. Unless otherwise indicated herein or context otherwise clearly conflicts, all methods described herein can be performed in any suitable order. Using any and all examples or exemplary language (for example, "such as" provided about the specific embodiment of this paper) is only intended to better illustrate the present invention, and is not intended to limit the scope of the present invention to which protection is otherwise claimed. The language in the specification should not be interpreted as representing any unclaimed element that is essential to the practice of the present invention.

[0024] The group of the replacement element of the present invention disclosed herein or embodiment should not be construed as limiting.Each group member can be mentioned and claimed individually or in any combination with other members of the group or other elements found herein.For convenience and / or patentability reasons, one or more members of the group may be included in the group or deleted from the group.When any such inclusion or lack occurs, description is deemed to comprise the group modified at this, so as to meet the written description of all Markush (Markush) groups used in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of an isometric view of a system according to an embodiment of the inventive subject matter.

[0026] Figure 2 A detailed view of a shield body cover according to an embodiment of the inventive subject matter is shown.

[0027] Figure 3 and Figure 4 A top view and a front view of the elements arranged on the platform of the fixed section are shown respectively.

[0028] Figure 5 A perspective view of the system with a double-sided PCBA installed is shown, illustrating how the system works in operation. DETAILED DESCRIPTION

[0029] Throughout the following discussion, many references will be made to servers, services, interfaces, engines, modules, clients, peers, portals, platforms, or other systems formed from computing devices. It should be understood that the use of these terms is considered to mean one or more computing devices having at least one processor (e.g., ASIC, FPGA, DSP, x86, ARM, ColdFire, GPU, multi-core processor, etc.) programmed to execute software instructions stored on a computer-readable tangible non-transitory medium (e.g., hard drive, solid-state drive, RAM, flash memory, ROM, etc.). For example, a server may include one or more computers operating as a web server, database server, or other type of computer server in a manner that implements the described roles, responsibilities, or functions. It should be further understood that the disclosed computer-based algorithms, processes, methods, or other types of instruction sets may be implemented as a computer program product that includes a non-transitory, tangible computer-readable medium storing instructions that cause a processor to perform the disclosed steps. Different servers, systems, databases, or interfaces can use standardized protocols or algorithms to exchange data, perhaps based on HTTP, HTTPS, AES, public-private key exchange, web service APIs, known financial transaction protocols, or other electronic information exchange methods. Data exchange may occur over a packet-switched network, the Internet, a LAN, a WAN, a VPN, or other types of packet-switched networks.

[0030] The following discussion provides a number of exemplary embodiments of the present subject matter. Although each embodiment represents a single combination of inventive elements, the present subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment includes elements A, B, and C, and a second embodiment includes elements B and D, the present subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0031] Figure 1 A schematic diagram of an isometric view of a system 100 according to an embodiment of the inventive subject matter is provided.

[0032] System 100 may generally be considered to include a stationary section and a cooling section.

[0033] The fixing section includes a holder 210 and a hot air gun 240 that heats the area with the defective chips for removal. The holder 210 is generally considered to be where the double-sided PCBA is attached to the system and the mechanism that holds it in place during the processing discussed herein.

[0034] The holder 210 may include a clamp or other restraining device that can securely hold the double-sided PCBA when installed so that it does not move during the defective chip removal process. In an embodiment, the holder 210 may be a cavity shaped to receive the PCBA, so that the PCBA is placed into the cavity and the shape of the cavity holds the PCBA in place.

[0035] like Figure 1 As shown, the fixed section includes a pair of rails 220, the length of which surrounds the holder 210. In the embodiment shown here, the rails 220 are arranged so that they are close to both sides of the PCBA installed in the holder 210. The fixed section also includes at least one shield body cover 230 (a pair of shield body covers 230 are shown in the embodiment here), which is slidably disposed on the rails 220 so that its position relative to the installed PCBA can be adjusted.

[0036] The figures herein show a pair of rails 220. However, it should be understood that a system having a single rail is also contemplated.

[0037] Figure 2 A detailed view of a shield body cover 230 is shown in accordance with an embodiment of the inventive subject matter.

[0038] The shield body cover 230 is made of a heat-resistant material that protects the BGA chip underneath the shield body cover from the heat generated by the hot air gun 240 during the extraction process, as will be explained in more detail below. Figure 1 As shown, the shield body cover 230 is disposed on the track 220 so that the position of the shield body cover 230 can be adjusted opposite to the double-sided PCBA installed in the fixed section.

[0039] The shield body cover 230 includes a sliding cover 231, which is also made of a heat-resistant material (which can be the same or different material as the rest of the shield body cover 230). An example of a suitable heat-resistant material that can be used for the shield body cover 230 and the sliding cover 231 is mica, but other heat-resistant materials are also contemplated. The sliding cover 231 can slide upward into an open position and then slide downward into a closed position, such as Figure 2 In the open position, the sliding cover 231 provides sufficient clearance above the BGA of the PCBA so that the shield body cover 230 can be properly adjusted along the track 220. When the sliding cover 231 slides downward to the closed position, the sliding cover 231 shields the BGA behind it from the heat generated by the hot air gun 240.

[0040] return Figure 1, a hot air gun 240 includes a heat source 241 and a muzzle tube 242. The heat source 241 may include a heating element and a fan or other form of fluid conductor to push hot air downward through the muzzle tube 242 and out of the muzzle tube 242. The muzzle tube 242 is typically positioned centrally above the area where the double-sided PCBA is mounted within the fixed section, so that the defective BGA chip to be removed is aligned with the open end of the muzzle tube 242.

[0041] The sliding shield body cover 230 is used to shield the BGA chips adjacent to the defective BGA chip to be removed. The cooling section is used to protect the BGA chips on the second side of the double-sided PCBA, including the BGA chips on the second side that may be directly opposite the defective BGA chip.

[0042] It is contemplated that the rails 220 may extend further than depicted in the exemplary figures included herein to allow sufficient space for installing and removing PCBAs of varying lengths.

[0043] In embodiments of the present subject matter, other methods for adjusting the position of the shield body cover 230 may be used. For example, the track 220 may instead be a series of tabs (male members) or gaps (female members), wherein the shield body cover 230 has corresponding gaps (female members) or tabs (male members), respectively, such that the cover 230 can mate with the tabs / gaps of the track 220, such that the position of the shield body cover 230 can be adjusted opposite to the track 220.

[0044] The cooling section includes a cooling source 310, a heat dissipation pipe 320, at least one heat dissipation element 340 (two are shown herein), the heat dissipation pipe 320 is partially coated in a heat-resistant coating 330, and the at least one heat dissipation element 340 has a heat dissipation medium 350 disposed thereon. Figure 1 The heat dissipation medium 350 is depicted by the patterned surface. The heat dissipation element 340 can be a high heat dissipation alloy element made of a high heat dissipation alloy. Preferably, the heat dissipation element 340 dissipates heat faster than the heat pipe 320.

[0045] In an embodiment of the present subject matter, heat dissipation medium 350 may include thermally conductive paste.

[0046] The heat-resistant coating 330 may be a layer of glue or other heat-resistant material coating at least a portion of the tube 320. In an embodiment, the heat-resistant coating 330 may be a coating material of heat-resistant / insulating material wrapped around at least a portion of the tube 320. The end of the tube 320 that contacts the BGA chip is not coated, such as Figure 1 shown.

[0047] Cooling source 310 includes a cooling fan or other form of fluid conducting equipment and a cooling element (e.g., a refrigerant system or other cooling system known in the art). Cooling source is coupled to heat pipe 320 so that air can be cooled by the cooling element and pushed through heat pipe 320 by the fan.

[0048] The heat pipe 320 may be made of heat dissipation alloy or other heat dissipation materials.

[0049] like Figure 1 As shown, the heat pipe 320 extends into the fixed section so that it is aligned with the end of the muzzle tube 242. The heat pipe 320 is positioned so that when a double-sided PCBA board is installed, the BGA chip opposite to the defective BGA chip to be removed contacts the heat pipe 320. It should be noted that this section of the heat pipe 320 is not covered by the heat-resistant coating 330. The heat-resistant coating 330 (through Figure 1 The heat resistant coating 330 is shown on only one side (the top side) of the heat resistant pipe 320. However, it is contemplated that the heat resistant coating 330 may cover multiple sides of the section of the pipe 320 shown, including covering the pipe 320 on all sides.

[0050] Near the end of the heat pipe 320, there is an exposed surface that is not covered by the heat resistant coating 330. This section will be in contact with the BGA chip, which will be described in further detail below.

[0051] Heat dissipating elements 340 are disposed on either side of the end sections of heat pipe 320 such that each heat dissipating element 340 is aligned with one or more BGA chips on the second side of the PCBA that are adjacent to the BGA chip opposite the defective BGA chip.

[0052] The heat dissipation medium 350 is provided on one side of the heat dissipation member 340 facing the mounted PCBA so that the corresponding BGA chip (the BGA chip opposite to the defective BGA chip) contacts the heat dissipation medium 350 when the PCBA is mounted.

[0053] It should be noted that in the embodiments of the inventive subject matter discussed herein, heat dissipation element 340 does not contact heat pipe 320. This allows chips in contact with heat dissipation element 340 (via heat dissipation medium 350) to dissipate heat at a different rate than chips in contact with heat pipe 320. The heat dissipation rate of heat pipe 320 is lower than the heat dissipation rate of heat dissipation element 340 (e.g., a heat sink). This prevents chips opposite a defective chip from dissipating heat too quickly and thus interfering with the removal process by making it more difficult to properly heat the solder of the defective chip for removal.

[0054] In embodiments of the present subject matter, such as the one illustrated herein, heat dissipating element 340 comprises a heat sink. However, other heat dissipating structures, such as other heat dissipating alloy structures, are suitable for the heat transfer purposes discussed herein.

[0055] In an embodiment of the present subject matter, certain elements of system 100 may be disposed on platform 400, which may be considered part of the fixed segment. Figure 3 and Figure 4 The top and front views of these components arranged on platform 400 are shown, respectively. Platform 400 is typically made of a rigid material and provides support for the PCBA holder and rail 220. Preferably, platform 400 is made of a rigid material with low thermal conductivity. Suitable materials may include wood, plastic, cardboard, etc. Metal with rubber, plastic, or other components may also be used to prevent unnecessary heat dissipation.

[0056] exist Figure 3 In the view of FIG. 2 , the hot air gun 240 is not shown so that the assembly of the remaining components can be clearly seen.

[0057] Figure 3 The alignment of the various components is shown from a top view. This view shows that the track 220 has a sliding shield body cover 230 attached thereto, allowing the sliding shield body cover 230 to slide along the track 220 into a desired position. The top view also shows how the heat pipe 320 and the heat dissipating element 340 (with the heat dissipating medium 350 disposed on top) are aligned opposite the track 220.

[0058] In embodiments of the present subject matter utilizing platform 400 , certain elements of the system may be disposed within cavities within platform 400 . Figure 4 The front view of FIG shows how the heat pipe 320 and the heat dissipating element 340 are arranged in a cavity within the platform 400. The rail 220 is arranged on the surface of the platform 400. The cavity of the platform 400 containing the heat pipe 320 can be sized so that the open end of the heat pipe 320 extends into the environment. Figure 3 In the view shown, the heat pipe 320 will exhaust air in a direction "towards" the page.

[0059] In an embodiment, when the tubes 320 are disposed in their corresponding cavities within the platform 400 , the platform 400 may help isolate the portions of the heat pipes 320 that contact the platform 400 .

[0060] Figure 5 Shown Figure 1 A perspective view of the system 100 with the double-sided PCBA 500 installed shows how the system works in operation. The double-sided PCBA 500 has symmetrically arranged BGA chips on both sides. For clarity, Figure 5 Platform 400 is not shown in FIG. 1 , but it will be appreciated that platform 400 or other platforms may be used to support the system during operation.

[0061] Double-sided PCBA 500 has a first side 510 and a second side 520. The first side includes a defective BGA chip 511 and a series of non-defective BGA chips 512. The second side 520 includes a series of non-defective BGA chips, including a BGA chip 521 directly opposite the defective BGA chip 511 and another BGA chip 522 opposite the non-defective BGA chip 512 on the first side.

[0062] like Figure 5 As shown, a double-sided PCBA 500 is positioned on a holder 210 (not shown) within a fixed section so that a defective BGA chip 511 is aligned with the end of the muzzle tube 242 of the hot air gun 240. The shield body cover 230 (with the sliding cover 231 open) moves along the track 220 so that the shield body cover 230 covers the BGA chips 512a and 512b adjacent to the defective chip 511. In embodiments of the present subject matter (such as the one shown here), the cover 230 can cover more than just the adjacent chips 512a and 512b, thereby protecting more of the BGA chips 512 on the first side 510.

[0063] Figure 5 It also shows how the BGA chip 521 contacts the heat pipe 320, and how the adjacent chips 522a, 522b contact the heat dissipation medium 350 spread on the top surface of the heat dissipation element 340. Other BGA chips 522 besides the adjacent BGA chips 522a, 522b may also contact the heat dissipation medium 350. Figure 5 This is the case in the example.

[0064] The operation of the system 100 is as follows:

[0065] The hot air gun 240 blows hot air toward the defective BGA chip 511 through the muzzle tube 242, as shown by the arrow. The shield body cover 230 (with the sliding cover 231 closed) covers the adjacent BGA chips 512a and 512b to protect them from the heat of the hot air.

[0066] When this occurs, cooling source 310 cools the air and sends it down heat pipe 320. Heat-resistant coating 330 prevents any external heat from heating the cooling air as it travels down pipe 320. As the air cools the surface of pipe 320, the opposite, lower temperature of pipe 320, which is in contact with the opposite BGA chip 521, causes heat to escape from BGA 521 and transfer to pipe 320, where it can be dispersed through the open end of pipe 320, as indicated by the arrows. Furthermore, any heat received by adjacent BGA chips 522a, 522b is transferred via heat dissipation medium 350 and then dissipated via heat sink 340.

[0067] The hot air from the muzzle tube 242 heats the solder joints beneath the defective BGA chip 511 , causing them to soften into molten solder jelly, thereby allowing the defective BGA chip 511 to be easily removed from the double-sided PCBA 500 .

[0068] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (where two elements being coupled to each other are in contact with each other) and indirect coupling (where at least one additional element is located between the two elements). Thus, the terms "coupled to" and "coupled with" are used synonymously.

[0069] It will be clear to those skilled in the art that, without departing from the inventive concept herein, more modifications may be made in addition to those already described. Therefore, the subject matter of the present invention is not limited except in the spirit of the appended claims. Furthermore, when interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. Specifically, the terms "comprises" and "comprising" should be interpreted as referring to elements, parts or steps in a non-exclusive manner, indicating that the elements, parts or steps mentioned may exist, or be utilized, or be combined with other elements, parts or steps not explicitly mentioned. When the specification claims relate to at least one thing selected from the group consisting of A, B, C... and N, the text should be interpreted as requiring only one element from the group, rather than A plus N, or B plus N, etc.

Claims

1. A system for removing BGA chips for a double-sided PCBA having symmetrically arranged BGA chips on both a first side and a second side of the PCBA, the system comprising: A fixed section, the fixed section comprising: a holder configured to hold the double-sided PCBA in the fixing section; a hot air gun comprising a hot air source and a muzzle tube having an end arranged to align with the defective BGA on the first side of the double-sided PCBA; At least one heat-resistant shield body cover is movably arranged along the track so that the at least one heat-resistant shield body cover can move above the first side and along the long axis of the double-sided PCBA so that the at least one heat-resistant shield body cover positionable over a first adjacent BGA chip adjacent to the defective BGA chip; and A cooling section, comprising: Cooling source; a heat pipe fluidly coupled to a cooling fan at a first end and aligned with an end of the muzzle pipe at a second end such that the second end is aligned with a first opposite BGA chip disposed on the second side of the PCBA and opposite the defective BGA chip; at least one heat dissipating element disposed along the second side of the PCBA, the at least one heat dissipating element aligned with at least one second opposing BGA chip disposed on the second side of the PCBA, the at least one second opposing BGA chip positioned adjacent to the first opposing BGA chip on the second side of the PCBA; and A heat dissipation medium layer is provided on a side surface of the at least one heat dissipation element facing the second side surface of the PCBA.

2. The system according to claim 1, wherein: The at least one heat-resistant shield body cover further includes a sliding cover provided on a side of the at least one heat-resistant shield body cover facing the muzzle barrel.

3. The system of claim 1 , further comprising at least one second heat-resistant shield body cover, the second heat-resistant shield body cover being movably disposed along the track so that the at least one second heat-resistant shield body cover can be positioned over a second adjacent BGA chip adjacent to the defective BGA chip.

4. The system according to claim 1, wherein: The at least one heat-resistant shield body cover is made of a heat-resistant alloy.

5. The system according to claim 1, wherein The at least one heat dissipation element is made of a high heat dissipation alloy.

6. The system according to claim 1, wherein: The heat dissipation pipe is made of heat dissipation alloy.

7. The system according to claim 1, wherein: The holder and the at least one heat dissipation element are arranged such that the heat dissipation medium layer contacts the at least one second opposite BGA when the double-sided PCBA is coupled with the holder.

8. The system of claim 1, further comprising a heat resistant coating on at least a first side of the heat pipe.

9. The system according to claim 1, wherein: The at least one heat dissipating element includes at least one heat sink.

10. The system according to claim 1, wherein: The at least one heat-resistant shield body cover slides on the rail.

11. The system according to claim 1, wherein: The heat dissipation medium includes thermally conductive glue.

12. The system of claim 1, further comprising a platform, wherein The rail and the holder are disposed on a surface of the platform, the platform further comprising a cavity sized to receive the heat pipe and the at least one heat dissipating element.

13. The system of claim 1, wherein: The at least one resistant heat shield body cover is sized such that when the at least one resistant heat shield body cover is positioned over the first adjacent BGA chip, the at least one resistant heat shield body cover also covers at least one additional BGA chip.

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