Back unsealing method of flip chip

Abstract

The invention relates to the technical field of chip packaging, in particular to a back unsealing method for a flip chip, and the method specifically comprises the following steps: S1, confirming the internal structure of the flip chip, and positioning a position where a cover needs to be opened by laser; s2, thinning treatment is conducted on the position where laser uncovering is needed; s3, removing the residual plastic package body material on the back surface of the flip chip after the thinning treatment; and S4, cleaning the flip chip after the residual plastic package body material is removed. According to the method for thinning the plastic package body by laser, the thinning depth can be accurately controlled, damage to the back surface of the chip caused by excessive thinning is prevented, meanwhile, the thinning progress is continuously monitored in the laser thinning process, and it can be ensured that the substrate is just exposed and cannot be further damaged.

Description

Technical Field

[0001] The invention relates to the technical field of chip packaging, in particular to a backside unsealing method for a flip chip. Background Art

[0002] In the field of electronic manufacturing, with the development of integrated circuit (IC) technology, chip packaging forms are becoming more and more diverse. Among them, flip chip (FC), as an advanced packaging method, has been widely used in high-density, high-performance electronic products.

[0003] However, during the production process, some chips may fail or have performance problems due to various reasons. In order to find out the causes of these problems and repair them, it is often necessary to unpack these chips to observe their internal structure and working status. Traditional unpacking methods mainly include chemical unpacking and flat grinding.

[0004] The chemical decapsulation method uses a specific chemical corrosive agent to dissolve the plastic encapsulation material on the surface of the chip at a certain temperature to expose the internal circuit. Although this method can effectively remove the plastic encapsulation layer, it is easy to damage the surrounding components due to the need for heating and the use of chemicals, and the operation is also relatively complicated.

[0005] In contrast, the flat grinding method is a physical unsealing method, which uses a grinder to grind the chip surface and gradually remove the plastic sealing layer. This method is relatively simple, but it is only applicable to the unsealing of a single IC product, and is not applicable to FC products soldered on PCB boards.

[0006] Therefore, in view of the above problems, the present invention proposes a new flip chip back side unsealing method, aiming to solve the deficiencies in the prior art and provide a safer, more efficient and more adaptable unsealing solution. Summary of the invention

[0007] The object of the present invention is to provide a backside unsealing method for a flip chip to solve the problems raised in the above background technology.

[0008] The technical solution of the present invention is: a back-side unsealing method for a flip chip, the back-side unsealing method specifically comprising the following steps:

[0009] S1: Confirm the internal structure of the flip chip and locate the position where laser cover needs to be opened;

[0010] S2: performing thinning processing on the position where the cover needs to be opened by laser;

[0011] S3: removing the residual plastic packaging material on the back of the flip chip after the thinning process;

[0012] S4: cleaning the flip chip after removing the residual plastic packaging material.

[0013] Furthermore, in the step S1, the internal structure of the flip chip is confirmed by X-ray detection or scanning acoustic microscopy technology.

[0014] Furthermore, in the step S1, the flip chip is positioned by using an X-ray positioning technology or a SAT positioning technology.

[0015] Furthermore, in step S2, the position where the laser cover needs to be opened is framed by a laser cover opening machine, and laser thinning is performed.

[0016] Furthermore, in step S3, the tools used to remove the residual plastic packaging material on the back of the flip chip after the thinning process include but are not limited to anti-static plastic tweezers and cotton swabs.

[0017] Furthermore, the laser energy and the number of laser irradiations are set according to the type of the flip chip and the material of the plastic package. At the same time, after each laser irradiation, the flip chip needs to be inspected to determine the thinning depth of the flip chip.

[0018] The present invention provides a back-side unsealing method for a flip chip by improvement, which has the following improvements and advantages compared with the prior art:

[0019] First, the laser thinning method of the present invention can accurately control the thinning depth to prevent damage to the back of the chip caused by excessive thinning. At the same time, the thinning progress is continuously monitored during the laser thinning process to ensure that the substrate is just exposed without further damage.

[0020] Second, the present invention combines X-ray positioning technology with SAT positioning technology to accurately determine the position and internal structure of the flip chip, thereby helping to improve the accuracy of the subsequent unsealing process. At the same time, non-contact X-ray scanning is used as the initial positioning to avoid chip damage that may be caused by physical contact. The more detailed internal structure information provided by SAT technology helps to more accurately control the unsealing process and reduce potential damage to the chip.

[0021] Thirdly, the present invention uses anti-static tweezers or cotton swabs for preliminary cleaning, and then uses ultrasonic cleaning, which can effectively remove residual plastic packaging materials without causing additional physical stress to the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 The present invention is a schematic flow chart of the back side unsealing method of the flip chip. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that, in the description of the present invention, the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0026] Furthermore, it should be understood that for the sake of ease of description, the sizes of the various components shown in the drawings are not drawn according to actual proportions. For example, the thickness or width of certain layers may be exaggerated relative to other layers.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined or described in one drawing, it will not require further detailed discussion and description in the description of the subsequent drawings.

[0028] refer to Figure 1 This embodiment provides a back-side unsealing method for a flip chip, which can completely preserve the chip structure and retain effective information, and plays an important role in determining a subsequent detection plan.

[0029] In this embodiment, the back side unsealing method of the flip chip specifically includes the following steps:

[0030] Step S1: Confirm the internal structure of the flip chip through X-ray detection or scanning acoustic microscopy technology, and locate the position where laser opening is required.

[0031] In this embodiment, the flip chip to be opened is positioned and marked to determine the required positioning picture. Specifically, in this embodiment, the flip chip to be opened is positioned by X-ray positioning technology or SAT positioning technology.

[0032] Furthermore, the flip chip to be opened is positioned by X-ray positioning technology, and a preliminary positioning picture is obtained. That is, an X-ray detector is prepared and adjusted to preset parameters, and the flip chip to be opened is placed in the X-ray detector, and the X-ray detector is started to scan the flip chip to be opened, so as to obtain a preliminary positioning picture by scanning. It is worth noting that the preliminary positioning picture can show the approximate position and internal structure of the flip chip to be opened.

[0033] At the same time, the preliminary positioning picture obtained above is compared with the preset positioning picture. When the difference between the preliminary positioning picture obtained above and the preset positioning picture is greater than the preset difference, the obtained preliminary positioning picture is further positioned. Otherwise, the preliminary positioning picture obtained above is the required positioning picture.

[0034] That is to say, the preliminary positioning picture obtained above is compared with the preset positioning picture. It is worth noting that the preset positioning picture here can be a previously known normal chip layout diagram or design drawing.

[0035] By comparing the obtained preliminary positioning picture with the preset positioning picture, the difference between the two is determined. When the difference between the two is less than the preset difference, the preliminary positioning picture is considered to be sufficiently accurate. Otherwise, the obtained preliminary positioning picture is further positioned.

[0036] Specifically, the flip chip to be opened is positioned by using the SAT positioning technology, and a secondary positioning picture is obtained, and the secondary positioning picture is the required positioning picture.

[0037] In this embodiment, when there is a large difference between the preliminary positioning picture and the preset positioning picture, it means that the X-ray positioning is not accurate enough, and the SAT positioning technology needs to be used for re-positioning.

[0038] Specifically, the flip chip to be unpacked is placed in the SAT device, and the device is started to scan the flip chip to be unpacked to obtain a secondary positioning image of the flip chip to be unpacked, and the secondary positioning image can provide more accurate chip position information.

[0039] It is worth noting that after comparing the secondary positioning picture with the preset positioning picture, when the difference between the secondary positioning picture and the preset positioning picture is less than the preset difference, the secondary positioning picture is considered to be the required positioning picture. Otherwise, the currently obtained secondary positioning picture still does not meet the requirements, and the SAT equipment parameters need to be readjusted to obtain the secondary positioning picture again.

[0040] Furthermore, after the required positioning picture is determined, marks are made around the flip chip according to the required positioning picture, and it is ensured that the marks are clearly visible and will not cause permanent damage to the circuit board.

[0041] Step S2: Thinning the plastic package shell of the flip chip by laser energy. In this embodiment, the plastic package shell of the flip chip is thinned by laser energy, and during the laser thinning process, the laser is irradiated until the substrate on the back of the flip chip is exposed.

[0042] It is worth noting that before laser treatment, the laser energy and the number of laser treatments must be set according to the type of flip chip and the material of the plastic package. At the same time, after each laser treatment, the flip chip must be inspected and confirmed under an optical microscope, and the thinning depth of the flip chip must be determined from the front and side of the flip chip. Specifically, once the substrate on the back of the flip chip is exposed, the laser treatment can be stopped.

[0043] Step S3: For the flip chip after laser irradiation in step S2, the remaining plastic package shell needs to be removed by tools until the back of the flip chip is completely exposed. It is worth noting that in the process of exposing the back of the flip chip, the back of the flip chip cannot be completely exposed. That is, the number of laser irradiations needs to be controlled to avoid excessive laser irradiations, which may cause ablation damage on the surface of the flip chip.

[0044] Specifically, the chip corresponding to the thinned plastic package shell is preliminarily cleaned by the tool. In this embodiment, the tool can be anti-static plastic tweezers or cotton swabs, etc., to preliminarily clean the chip, so as to facilitate subsequent cleaning.

[0045] Step S4: The chip after preliminary cleaning is subsequently cleaned by ultrasonic wave to remove resin, dirt or other tiny particles on the chip. This process can not only fully expose the back substrate of the chip, but also will not cause mechanical stress damage to the chip.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for opening the back side of a flip chip, characterized in that: The back opening method specifically includes the following steps: S1: Confirm the internal structure of the flip chip and locate the position where laser cover needs to be opened; S2: performing thinning processing on the position where the cover needs to be opened by laser; S3: removing the residual plastic packaging material on the back of the flip chip after the thinning process; S4: cleaning the flip chip after removing the residual plastic packaging material.

2. The back side opening method of a flip chip according to claim 1, characterized in that: In the step S1, the internal structure of the flip chip is confirmed by X-ray detection or scanning acoustic microscopy technology.

3. The back side opening method of a flip chip according to claim 1, characterized in that: In the step S1, the flip chip is positioned by using X-ray positioning technology or SAT positioning technology.

4. The back side opening method of a flip chip according to claim 1, characterized in that: In the step S2, the position where the cover needs to be opened by laser is framed by a laser opening machine, and laser thinning is performed.

5. The back side opening method of a flip chip according to claim 1, characterized in that: In the step S3, the tools used to remove the residual plastic packaging material on the back of the flip chip after the thinning process include but are not limited to anti-static plastic tweezers and cotton swabs.

6. The back side opening method of a flip chip according to claim 1, characterized in that: The laser energy and the number of laser irradiations are set according to the type of the flip chip and the material of the plastic package. At the same time, after each laser irradiation, the flip chip needs to be inspected to determine the thinning depth of the flip chip.

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