A method and apparatus for reworking solder balls in BGA products

Abstract

This invention discloses a method and apparatus for reworking solder balls in BGA products. The method includes: attaching cutting adhesive tape to the bottom surface of a fixture and placing IC chips into the fixture; removing solder balls from the IC chips using a cutting machine; replacing the cutting adhesive tape on the fixture with high-temperature adhesive tape; placing the fixture into a ball-mounting machine to re-mount the IC chips; and performing reflow, cleaning, and drying on the re-mounted IC chips. This invention achieves automatic solder ball removal by combining a fixture and a cutting machine, avoiding defects such as insufficient solder removal, exposed copper, and rosin residue on IC chips, thus improving the success rate of IC chip rework. It also enables batch rework of IC chips and improves the rework efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method and apparatus for reworking solder balls in BGA products. Background Technology

[0002] Ball grid array (BGA) is a packaging method for integrated circuits. BGA offers advantages such as good coplanarity, a large number of I / Os, high assembly density, good electrical and thermal performance, and self-calibration during soldering, leading to its increasingly widespread use.

[0003] BGA chips have an array of solder balls arranged on their bottom surface. During the ball placement, transportation, and storage processes, some solder balls may be missing. Therefore, it is necessary to remove the solder from BGA chips with missing solder balls. There are two existing methods for removing solder, as shown below:

[0004] 1. Soldering iron desoldering method: The main process is as follows: heat the solder ball with a soldering iron. When the solder ball is in a molten state, use the soldering iron to remove the molten solder. Then clean and dry the BGA chip. Finally, use the manual stencil to remove the solder ball and re-replace the ball.

[0005] 2. Vacuum tube desoldering method: The main process is as follows: heat the solder ball with a hot air gun, and remove the solder ball with a vacuum suction pen while it is in a molten state.

[0006] The soldering iron method for removing solder balls has the following problems:

[0007] 1) Insufficient removal of solder balls results in uneven solder ball surfaces, which is not conducive to re-balling. Furthermore, re-balling can lead to problems such as solder balls being too large or too high.

[0008] 2) Using a soldering iron to remove molten solder can scratch the product and even damage the green solder mask, causing the copper to be exposed.

[0009] 3) During the desoldering process, soldering irons can easily cause rosin to carbonize and remain on the product, which is extremely difficult to remove;

[0010] 4) The repair speed is slow and cannot meet the requirements for batch repair.

[0011] However, the desoldering efficiency of the vacuum tube desoldering method is low and cannot meet the requirements of batch rework. Summary of the Invention

[0012] The purpose of this invention is to provide a method and apparatus for reworking solder balls in BGA products, aiming to solve the problems of low desoldering efficiency and inability to meet the requirements of batch rework in the existing technology.

[0013] This invention provides a method for reworking solder balls in BGA products, comprising:

[0014] Attach cutting adhesive paper to the bottom of the fixture and place the IC chip into the fixture;

[0015] The solder balls on the IC chips are removed using a cutting machine;

[0016] Replace the cutting adhesive paper on the fixture with high-temperature adhesive paper;

[0017] The fixture is placed into the ball-planting machine to plant the IC particles;

[0018] The IC chips after ball implantation undergo reflow, cleaning, and drying.

[0019] Furthermore, the step of applying cutting adhesive tape to the bottom surface of the fixture includes:

[0020] An isolation rod is provided inside the fixture to separate the IC particles, and cutting mark points are provided at intervals at both ends of the top surface of the fixture.

[0021] Furthermore, the provision of an isolation rod within the fixture to separate the IC particles includes:

[0022] A separation bar with a cutting width of 0.25±0.05mm is provided inside the fixture to separate the IC particles.

[0023] Furthermore, the step of setting cutting mark points at intervals at both ends of the fixture includes:

[0024] Cutting markers are set at intervals such that the width of the overlapping portion of the second cut and the first cut is 15%-25% of the width of the first cut.

[0025] Furthermore, the removal of solder balls from the IC particles using a cutting machine includes:

[0026] Adjust the height of the cutting machine to be on the same horizontal plane as the cutting surface of the fixture.

[0027] Furthermore, replacing the cutting adhesive tape on the fixture with high-temperature adhesive tape includes:

[0028] The cutting adhesive paper on the vacuum fixture is replaced with high-temperature adhesive paper.

[0029] Furthermore, the process of replacing the cutting adhesive paper on the fixture with high-temperature adhesive paper using a vacuum fixture includes:

[0030] The fixture is subjected to ultraviolet light to remove the stickiness of the cutting adhesive paper.

[0031] This invention also provides a BGA product solder ball rework device, including: a jig, cutting tape, a cutting machine, high-temperature tape, and a ball repositioning machine;

[0032] The fixture is used to install IC chips;

[0033] The cutting adhesive tape is used to fix the IC particles inside the fixture;

[0034] The cutting machine is used to remove solder balls from the IC particles;

[0035] The high-temperature adhesive tape is used to fix the IC particles inside the fixture;

[0036] The ball-planting machine is used to implant solder balls onto the IC chips.

[0037] Furthermore, it also includes a vacuum fixture for replacing the cutting adhesive paper with the high-temperature adhesive paper.

[0038] Furthermore, the cutting machine is a tape saw cutting machine.

[0039] This invention provides a method for reworking solder balls in BGA products, comprising: attaching cutting adhesive paper to the bottom surface of a fixture and placing IC chips into the fixture; removing solder balls from the IC chips using a cutting machine; replacing the cutting adhesive paper on the fixture with high-temperature adhesive paper; placing the fixture into a ball-mounting machine to remount the IC chips; and performing reflow, cleaning, and drying on the remounted IC chips. This invention achieves automatic solder ball removal by combining a fixture and a cutting machine, avoiding defects such as insufficient solder removal, exposed copper, and rosin residue on the IC chips, thus improving the success rate and efficiency of IC chip rework. Simultaneously, the use of fully automated ball-mounting equipment enables re-balling, transforming manual processes into automatic ones, and achieving batch rework of IC chips. This invention also provides a BGA product solder ball rework device, which has the same effects as the above method, and will not be described in detail here. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart illustrating the BGA product solder ball rework method of this embodiment;

[0042] Figure 2 This is a schematic diagram of the fixture structure;

[0043] Figure 3 Schematic diagram for setting up cutting marker points;

[0044] Figure 4 This is a schematic block diagram of the BGA product solder ball rework device in this embodiment; Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0047] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0048] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0049] Please see Figure 1 This invention provides a method for reworking solder balls in BGA products, comprising:

[0050] S101: Attach cutting adhesive paper to the bottom surface of the fixture and place the IC chip into the fixture;

[0051] Please see Figure 2 Before placing IC chips into the fixture, the fixture needs to be designed and manufactured. In this embodiment, multiple isolation rods 1 are set inside the fixture to form an IC chip chamber 2 for placing IC chips. The size of the IC chip chamber 2 is the same as that of the IC chips. Cutting marks 3 are set at intervals at both ends of the top surface of the fixture for cutting calibration. Then, the distance between the cutting marks 3 of the fixture is set according to the size of the IC chips, the distribution of solder balls 4 and the spacing of the solder balls 4. The thickness of the fixture is the same as the thickness of the IC chips to be reworked. This fixture can process multiple IC chips at the same time, realizing batch processing of IC chips.

[0052] In one embodiment, multiple isolation bars 1 with a cutting width of 0.25±0.05mm are arranged inside the fixture to form an IC particle chamber 2. Cutting marks 3 are set at intervals on both ends of the top surface of the fixture in such a way that the cutting width of the overlapping part of the second cut and the first cut is 15%-25% of the cutting width of the first cut, so as to ensure that the solder balls 4 can be removed sufficiently.

[0053] For details, please refer to Figure 3 The shaded area represents the overlapping portion of the first and second cuts. Here, L1 represents the cutting width of the shaded area; L2 represents the cutting width of the second cut; and L3 represents the cutting width of the first cut. The cutting marker 3 is set at intervals of 15%-25% of the L1 / L3 value. The L1 / L3 value can be represented by Overlap.

[0054] In a specific application scenario, the diameter (ball size) of solder ball 4 is 0.4mm, the spacing between solder balls 4 is 1mm, the cutting width of the cutting machine is 0.3mm, and the distance between the cutting mark points 3 is set to 0.24mm. That is, the cutting mark points 3 are set at intervals with an overlap of 20%. Each row of solder balls 4 on the fixture only needs to be set with two pairs of cutting mark points 3 to remove the solder balls 4.

[0055] After designing and manufacturing the fixture, cutting tape needs to be attached to the bottom surface of the fixture. The IC chip is then placed into the fixture with its top surface facing upwards. That is, the bottom surface of the IC chip is covered with cutting tape and fixed inside the fixture by the cutting tape. After fixing, the top surface of the IC chip and the top surface of the fixture are at the same level. The solder ball 4 on the top surface of the IC chip is higher than the top surface of the fixture. This design ensures that only the solder ball 4 can be cut during cutting, without damaging other components on the IC chip.

[0056] S102: Remove solder balls from the IC chips using a cutting machine;

[0057] Before using a cutting machine to remove the solder balls 4 from the IC chip, the height of the cutting machine needs to be adjusted to be on the same level as the cutting surface of the fixture. Then, the solder balls 4 on the IC chip are cut off according to the spacing of the cutting marks 3.

[0058] S103: Replace the cutting adhesive paper on the fixture with high-temperature adhesive paper;

[0059] After removing solder ball 4, the IC chip needs to be reflowed. Therefore, the cutting adhesive tape on the fixture needs to be replaced with high-temperature adhesive tape. In this embodiment, a vacuum fixture is used to replace the cutting adhesive tape on the fixture with high-temperature adhesive tape.

[0060] The replacement process is as follows: the IC chip is irradiated with ultraviolet light (i.e., UV irradiation) to remove the stickiness of the cutting adhesive tape, making it easier to switch between the cutting adhesive tape and the high-temperature adhesive tape. During replacement, the fixture and the vacuum fixture are aligned, and the suction force of the vacuum fixture is used to hold the IC chip. Then the cutting adhesive tape is peeled off and the high-temperature adhesive tape is reapplied.

[0061] In one specific scenario, the IC chip is irradiated with ultraviolet light for 60 seconds. Then, the fixture is aligned with the vacuum fixture, and the suction of the vacuum fixture is used to hold the IC chip. Then, the cutting adhesive tape is peeled off, and high-temperature adhesive tape is applied.

[0062] Among them, high-temperature adhesive tapes can be made of polyimide tape, Teflon tape, Teflon pure film tape, high-temperature double-sided imide tape, glass cloth double-sided tape, masking tape, composite red and white masking tape, etc.

[0063] S104: Place the fixture into the ball-planting machine to plant the IC particles;

[0064] S105: Performs reflow, cleaning, and drying processes on IC chips after ball loading.

[0065] This embodiment removes the solder balls 4 from IC chips by combining a cutting machine and a fixture. It can process multiple IC chips at the same time, realizing batch removal of IC chips. Moreover, the IC chips do not need to be treated at high temperature during the removal process, which reduces the defect rate. In this embodiment, desoldering, adhesive tape replacement, ball repositioning, reflow, cleaning and drying can all be completed automatically, improving rework efficiency and achieving cost reduction and efficiency improvement.

[0066] Please see Figure 4 This embodiment also provides a BGA product solder ball rework device 400, including: a jig 401, cutting adhesive tape 402, a cutting machine 403, high-temperature adhesive tape 405, and a ball-mounting machine 406.

[0067] Fixture 401 is used to install IC chips;

[0068] Cutting tape 402 is used to fix IC chips inside the fixture;

[0069] The 403 cutting machine is used to remove solder balls from IC chips;

[0070] High-temperature adhesive tape 405 is used to fix IC chips inside the fixture;

[0071] The 406 ball-planting machine is used to implant solder balls onto IC chips.

[0072] Furthermore, the fixture 401 is also used to set isolation bars to separate IC particles, and to set cutting points at intervals at both ends.

[0073] Furthermore, the fixture 401 is also used to set a separation bar with a cutting width of 0.25±0.05mm to separate IC particles.

[0074] Furthermore, the fixture 401 is also used to set cutting points at intervals such that the overlap between the cutting width of the second cut and the cutting width of the first cut accounts for 15%-25% of the cutting width of the first cut.

[0075] Furthermore, the cutting machine 403 is also used to adjust the height to be in the same horizontal plane as the cutting surface of the fixture 401.

[0076] Furthermore, it also includes: a vacuum fixture 404, used to replace the cutting adhesive tape 402 with high-temperature adhesive tape 405.

[0077] Furthermore, the fixture 401 is also used for ultraviolet irradiation to remove the stickiness of the cutting adhesive paper 402.

[0078] Furthermore, the cutting machine is a tape saw, which is a band saw used for mass production of small-sized products.

[0079] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

[0080] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusivity.

[0081] The term "comprises" implies 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. Unless otherwise specified, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for reworking solder balls in BGA products, characterized in that, include: Attach cutting adhesive paper to the bottom of the fixture and place the IC chip into the fixture; The solder balls on the IC chips are removed using a cutting machine; Replace the cutting adhesive paper on the fixture with high-temperature adhesive paper; The fixture is placed into the ball-planting machine to plant the IC particles; The IC chips after ball implantation undergo reflow, cleaning, and drying processes. Before applying the cutting adhesive tape to the bottom surface of the fixture, the following steps are included: An isolation rod is provided inside the fixture to separate the IC particles, and cutting mark points are provided at intervals at both ends of the top surface of the fixture; The step of setting a separation bar within the fixture to separate the IC particles includes: A separation bar with a cutting width of 0.25±0.05 mm is provided inside the fixture to separate the IC particles; The step of setting cutting mark points at intervals at both ends of the fixture includes: Cutting markers are set at intervals such that the width of the overlapping portion of the second cut and the first cut is 15%-25% of the width of the first cut; The thickness of the fixture is the same as the thickness of the IC chip that needs to be repaired; The IC chip is placed into the fixture with its top surface facing upwards. After fixing, the top surface of the IC chip and the top surface of the fixture are at the same horizontal level, and the solder balls on the top surface of the IC chip are higher than the top surface of the fixture.

2. The BGA product solder ball rework method according to claim 1, characterized in that, The process of removing solder balls from the IC chip using a cutting machine includes: Adjust the height of the cutting machine to be on the same horizontal plane as the cutting surface of the fixture.

3. The BGA product solder ball rework method according to claim 1, characterized in that, The step of replacing the cutting adhesive paper on the fixture with high-temperature adhesive paper includes: The cutting adhesive paper on the vacuum fixture is replaced with high-temperature adhesive paper.

4. The BGA product solder ball rework method according to claim 3, characterized in that, Before replacing the cutting adhesive paper on the vacuum fixture with high-temperature adhesive paper, the following steps are included: The fixture is subjected to ultraviolet light to remove the stickiness of the cutting adhesive paper.

5. A BGA product solder ball rework device, characterized in that, include: Fixtures, cutting tape, cutting machines, high-temperature tape, and ball-planting machines; The fixture is used to install IC chips; The cutting adhesive tape is used to fix the IC particles inside the fixture; The cutting machine is used to remove solder balls from the IC particles; The high-temperature adhesive tape is used to fix the IC particles inside the fixture; The ball-planting machine is used to implant solder balls onto the IC particles; The fixture is equipped with an isolation rod to separate the IC particles, and cutting marks are provided at intervals at both ends of the top surface of the fixture; The fixture is equipped with a separation bar with a cutting width of 0.25±0.05 mm to separate the IC particles; Cutting markers are set at intervals such that the width of the overlapping portion of the second cut and the first cut is 15%-25% of the width of the first cut; The thickness of the fixture is the same as the thickness of the IC chip that needs to be repaired; When the IC chip is placed into the fixture with its top surface facing upwards, after it is fixed, the top surface of the IC chip and the top surface of the fixture are at the same horizontal level, and the solder balls on the top surface of the IC chip are higher than the top surface of the fixture.

6. The BGA product solder ball rework device according to claim 5, characterized in that, Also includes: A vacuum fixture is used to replace the cutting adhesive paper with the high-temperature adhesive paper.

7. The BGA product solder ball rework device according to claim 5, characterized in that, The cutting machine is a tape saw cutting machine.

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