CN110587385A - Method for thinning flip chip on circuit board, grinding drill bit and fixed base - Google Patents

Abstract

The application relates to a method for thinning a flip chip on a circuit board, a grinding drill bit and a fixed base; the method comprises the steps that the circuit board is pasted on the fixed base in a mode that a flip chip to be thinned on the circuit board is far away from the fixed base; pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; get rid of and grind the membrane, and paste polishing cloth on the grinding end face that grinds the drill bit, treat the back of attenuate flip chip and polish, the thickness of treating attenuate flip chip reaches preset polishing thickness, realize the direct attenuate of the flip chip of welding on the circuit board, reduce the number of times that will the flip chip follow circuit board dismantlement in the conventional art, reduce many times high temperature welding technology to the thermal damage of flip chip, thereby guarantee that the performance of flip chip around the attenuate is not impaired, improve the test verification around the attenuate widely, the efficiency of radiation test.

Description

Method for thinning flip chip on circuit board, grinding drill bit and fixed base

Technical Field

The application relates to the technical field of integrated circuit testing, in particular to a method for thinning a flip chip on a circuit board, a grinding drill bit and a fixed base.

Background

With the rapid development of aerospace industry in China, semiconductor devices and integrated circuits with high performance, high reliability, high integration level, low power consumption, light weight and small size are more and more popular. Flip chip packaging facilitates high-density, high-performance, and miniaturized packaging of chips, and has become an optimal choice for multi-function and high-I/O (Input/Output) pin packaging in recent years, such as high-end devices such as CPUs (central processing units), DSPs (digital signal processing chips), FPGAs (Field Programmable Gate arrays), and the like, and has been widely used.

In a severe radiation environment of a space, three radiation sources of a galaxy, a sun and a capture zone exist, and single event effect generated by high-energy heavy ions and protons in a space electronics system can cause the change of device logic state, data loss, function interruption, even large current burning failure and the like, thereby seriously threatening the safe operation of the spacecraft. In order to evaluate the risk of the aerospace component in-orbit events in advance, a radiation resistance evaluation test based on the ground needs to be carried out.

However, when the single event effect radiation test is performed on the flip-chip integrated circuit, the front radiation test of the chip cannot be realized, and heavy ions can only enter from the back of the chip and reach the active region after penetrating through the substrate. Moreover, the ground accelerator has limited energy and range of heavy ions, and cannot penetrate through the packaging material outside the chip, so the substrate needs to be thinned to a certain thickness (generally 100 micrometers) before the test, and the current technology needs to repeatedly disassemble and assemble the flip-chip packaged integrated circuit soldered on the circuit board to complete the test, so in the implementation process, the inventor finds that at least the following problems exist in the conventional technology: the traditional technology can not directly thin the flip-chip packaged integrated circuit welded on the circuit board.

Disclosure of Invention

Therefore, it is necessary to provide a method for thinning a flip chip on a circuit board and a grinding drill for solving the problem that the conventional technology cannot directly thin the flip chip packaged integrated circuit soldered on the circuit board.

In order to achieve the above object, in one aspect, an embodiment of the present application provides a method for thinning a flip chip on a circuit board, including the following steps:

pasting the circuit board on the fixed base in a mode that the flip chip to be thinned on the circuit board is far away from the fixed base;

pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; the grinding drill bit is a grinding drill bit with the diameter of the grinding end face corresponding to the width of the flip chip to be thinned;

and removing the grinding film, sticking polishing cloth on the grinding end face of the grinding drill bit, and polishing the back surface of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches the preset polishing thickness.

In one embodiment, the step of adhering a grinding film on the grinding end face of the grinding drill bit, grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness comprises the following steps:

pasting a first-granularity grinding film on the grinding end face of the grinding drill bit, and performing coarse grinding on the back face of the flip chip to be thinned until the preset coarse grinding thickness is reached;

removing the first-granularity grinding film, sticking a second-granularity grinding film on the grinding end face of the grinding drill bit, and finely grinding the back face of the flip chip to be thinned until the preset grinding thickness is reached; the second grain size milled film has a grain size smaller than that of the first grain size milled film.

In one embodiment, the first particle size abrasive film is a 45 micron particle size abrasive film.

In one embodiment, the second particle size abrasive film is a 30 micron particle size abrasive film.

In one embodiment, the step of removing the grinding film, adhering polishing cloth to the grinding end face of the grinding drill, and polishing the back surface of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset polishing thickness comprises the following steps:

removing the grinding film, sticking a first polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned for a preset time under the first-granularity diamond suspension;

and removing the first polishing cloth, sticking a second polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned under the second-granularity diamond suspension until the preset polishing thickness is reached.

In one embodiment, the first polishing cloth is a Kempad type polishing cloth; the first particle size diamond suspension was a 6 micron particle size diamond suspension.

In one embodiment, the second polishing cloth is Red Final C-type flocked cloth; the second particle size diamond suspension is a 1 micron particle size diamond suspension.

In one embodiment, the predetermined time period is 60 seconds to 90 seconds.

On the other hand, the embodiment of the application also provides a grinding drill bit for realizing the method for thinning the flip chip on the circuit board, which comprises the following steps:

the side wall of the first cylindrical structure is provided with a rectangular groove;

the diameter of the second cylindrical structure is larger than that of the first cylindrical structure, the first end face of the second cylindrical structure is mechanically connected with the first cylindrical structure, and the second end face of the second cylindrical structure is a grinding end face.

In another aspect, an embodiment of the present application further provides a fixing base for implementing a method for thinning a flip chip on a circuit board, where the fixing base includes a rectangular plate made of aluminum; a plurality of through holes for installation and fixation are formed in the aluminum rectangular plate.

One of the above technical solutions has the following advantages and beneficial effects:

the method for thinning the flip chip on the circuit board provided by the embodiments of the application adopts the following steps: pasting the circuit board on the fixed base in a mode that the flip chip to be thinned on the circuit board is far away from the fixed base; pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; get rid of and grind the membrane, and paste polishing cloth on the grinding end face that grinds the drill bit, treat the back of attenuate flip chip and polish, the thickness of treating attenuate flip chip reaches preset polishing thickness, realize the direct attenuate of the flip chip of welding on the circuit board, reduce the number of times that will the flip chip follow circuit board dismantlement in the conventional art, reduce many times high temperature welding technology to the thermal damage of flip chip, thereby guarantee that the performance of flip chip around the attenuate is not impaired, improve the test verification around the attenuate widely, the efficiency of radiation test.

Drawings

FIG. 1 is a flow chart of steps in a method for thinning a flip chip on a circuit board according to one embodiment;

FIG. 2 is a flow chart of the steps of the grinding step in one embodiment;

FIG. 3 is a flowchart of the steps of the polishing step in one embodiment;

FIG. 4 is an elevation view of an abrasive drill bit according to one embodiment;

FIG. 5 is a left side view of an abrasive drill bit according to one embodiment;

FIG. 6 is a top view of a mounting base in one embodiment.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element and be integral therewith, or intervening elements may also be present. The terms "open," "first end," "second end," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In a specific application scenario of the method for thinning the flip chip on the circuit board of the application:

the conventional technology provides a thinning method, which comprises three steps of pretreatment, fixing and grinding. Fixing the flip-chip packaged integrated circuit on a fixture by using hot melt wax in a mode that the back surface of the flip-chip faces outwards; and in the grinding step, the clamp fixed with the chip is locked on the grinding mechanical arm, the back of the chip is in a downward state after the clamp is locked, and then the chip is descended to the surface of the chip to be in contact with the grinding turntable, and the grinding and thinning are carried out by applying force. When thinning, the surface of the chip is always kept in a downward state. During grinding, if the surface periphery of the flip chip is not provided with the patch capacitor, the technical scheme can be utilized to directly grind and thin. If the surface periphery of the flip chip is provided with the patch capacitors, the patch capacitors need to be detached in advance, and then the chip is ground and thinned.

However, the conventional techniques have at least the following drawbacks: first, in the above scheme, the diameter of the clamp during grinding is about 5 cm, the diameter of the grinding turntable is about 20 cm, although the fixing requirements of most single flip chips can be met, the length or width of a common printed circuit board is at least more than 20 cm to tens of cm, and the back of the printed circuit board is provided with pins, so that the sample cannot be fixed by using the clamp, and the subsequent operation of other grinding steps cannot be performed; secondly, the surface of the chip is downward when the scheme is thinned, the grinding turntable is limited by the size of the grinding turntable and the structure of the original machine table, and the circuit board does not have enough space for rotation, so the scheme cannot be applied to the flip-chip packaged integrated circuit welded on the circuit board; thirdly, if need dismantle flip-chip package integrated circuit from the circuit board and carry out the attenuate according to above-mentioned scheme again, then flip-chip need experience a plurality of high temperature welding processes, if there is the paster electric capacity chip periphery, will increase again and dismantle the high temperature process of electric capacity and installation electric capacity, will increase again the risk of thermal stress to the thermal damage of circuit after the attenuate.

In order to solve the problem that the traditional technology can not directly thin the flip-chip packaged integrated circuit welded on the circuit board, in one embodiment, as shown in fig. 1, a method for thinning a flip chip on the circuit board is provided, which comprises the following steps:

and step S110, pasting the circuit board on the fixed base in a mode that the flip chip to be thinned on the circuit board is far away from the fixed base.

It should be noted that the fixing base is redesigned according to the structure of the chip thinning platform in the conventional technology (the structure of the fixing base can refer to the conventional technology, which is not described in detail in this application) and the manner of fixedly mounting the conventional base. The fixing base in the application can meet the fixing requirement of the existing circuit board with the length and width size range (generally 10 cm-50 cm).

The circuit board fixing step is as follows: selecting two adjacent edges on the fixed base, wherein one edge is used as an X axis, and the other edge is used as a Y axis, and establishing a coordinate system; selecting any vertex angle of the flip chip to be thinned as a zero point on the circuit board, and selecting an edge closest to the vertex angle on the circuit board as a reference edge; adhering a foam double-sided adhesive tape on the fixed base, inserting a contact pin on the back of the circuit board into the foam double-sided adhesive tape, and enabling the reference edge to be parallel to the X axis; after the circuit board is pasted on the fixed base through the foam double-sided adhesive, the flip chip to be thinned deviates from the fixed base, and the back of the flip chip to be thinned faces the grinding drill bit, so that the flip chip to be thinned is convenient; with unable adjustment base installation chip attenuate platform, under chip attenuate platform drives, unable adjustment base drives the circuit board motion, for treating the motion that the attenuate flip chip attenuate provided the relative grinding drill bit. In one example, the fixing base drives the circuit board to reciprocate along the Y axis and then along the X axis.

In order to grasp the initial thickness of the flip chip to be thinned, the specifications of the grinding film and the polishing film used in the thinning process and the time required for each process are preferably selected, and in one example, before the step of pasting the circuit board on the fixing base in such a manner that the flip chip to be thinned on the circuit board is away from the fixing base, the method further comprises the steps of:

the initial thickness of the flip chip to be thinned on the circuit board (typically 700 to 900 microns) is measured using multi-point thickness measurement.

Step S120, pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; the grinding drill bit is a grinding drill bit with the diameter of the grinding end face corresponding to the width of the flip chip to be thinned.

It should be noted that, before thinning the flip chip to be thinned, a grinding drill needs to be selected, and the diameter of the grinding end face used for grinding by the grinding drill is adapted to the width of the flip chip to be thinned, that is, the diameter of the grinding end face is equal to or slightly smaller than the width of the flip chip to be thinned. Wherein the diameter of the abrasive end face is selectable from 1 mm to 30 mm.

After the circuit board is fixed, paste on the grinding terminal surface that grinds the drill bit and grind the membrane, the grinding terminal surface that will grind the drill bit is close to towards treating attenuate flip chip, and contact the grinding terminal surface of treating attenuate flip chip, treat attenuate flip chip relative grinding drill bit motion under the drive of chip attenuate platform, begin to treat attenuate flip chip and carry out the attenuate, will treat attenuate flip chip attenuate to predetermineeing grinding thickness, wherein predetermine grinding thickness can be 50 microns, or slightly be greater than 50 microns, or slightly be less than 50 microns.

Further, in the course of grinding, need will treat a few drops of water or silicon oxide suspension on the back of attenuate flip chip, increase the degree of lubrication in the course of grinding to can not lead to the fact extra influence to other components and parts etc. on the circuit board at flip-chip package integrated circuit place.

Specifically, as shown in fig. 2, paste the grinding membrane on the grinding terminal surface of grinding drill bit, treat the back of attenuate flip chip and grind, reach the step of predetermineeing the grinding thickness until the thickness of treating attenuate flip chip, include:

step S210, a first-granularity grinding film is pasted on the grinding end face of the grinding drill bit, and coarse grinding is carried out on the back face of the flip chip to be thinned until a preset coarse grinding thickness is reached.

It should be noted that the particle size of the first-particle-size ground film may be determined according to actual needs, and for example, the particle size of the first-particle-size ground film may be selected from a range of particle sizes of 40 to 50 μm. Specifically, in one example, the first particle size abrasive film is a 45 micron particle size abrasive film. In the rough grinding process, the flip chip to be thinned is thinned to a preset rough grinding thickness, wherein the preset rough grinding thickness can be 60 micrometers, or slightly larger than 60 micrometers, or slightly smaller than 60 micrometers.

Step S220, removing the first-granularity grinding film, pasting a second-granularity grinding film on the grinding end face of the grinding drill bit, and finely grinding the back face of the flip chip to be thinned until the preset grinding thickness is reached; the second grain size milled film has a grain size smaller than that of the first grain size milled film.

It should be noted that the particle size of the second-particle-size ground film may be determined according to actual needs, and for example, the particle size of the second-particle-size ground film may be selected from a range of particle sizes of 25 micrometers to 35 micrometers. Specifically, in one example, the second particle size abrasive film is a 30 micron particle size abrasive film. And in the fine grinding process, thinning the flip chip to be thinned to a preset grinding thickness.

And step S130, removing the grinding film, sticking polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches the preset polishing thickness.

It should be noted that, after finishing grinding the flip chip to be thinned, the grinding film is replaced by polishing cloth, the flip chip to be thinned is polished, the flip chip to be thinned is thinned to a preset polishing thickness, and the preset polishing thickness is the thickness to be thinned to the final requirement of the flip chip to be thinned.

Specifically, as shown in fig. 3, the grinding film is removed, polishing cloth is pasted on the grinding end face of the grinding drill, the back face of the flip chip to be thinned is polished, and the step of polishing the thickness of the flip chip to be thinned to a preset polishing thickness is performed, including:

and S310, removing the grinding film, pasting first polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned for a preset time under the first-granularity diamond suspension.

It is noted that the specification and type of the first polishing cloth may be determined according to actual requirements, and in one example, the first polishing cloth is a Kempad type polishing cloth. The first size diamond suspension may be sized according to actual requirements, and in one example, the first size diamond suspension is a 6 micron size diamond suspension. The polishing time period may be determined according to the polishing requirements, and in one example, the preset time period is 60 seconds to 90 seconds.

Step S320, removing the first polishing cloth, pasting a second polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned under the second-granularity diamond suspension until the preset polishing thickness is reached.

It should be noted that the specification and type of the first polishing cloth can be determined according to actual requirements, and in one example, the second polishing cloth is Red Final C-type flocked cloth. The first size diamond suspension may be sized according to actual requirements, and in one example, the second size diamond suspension is a 1 micron size diamond suspension.

In order to ensure the flatness of the flip chip to be thinned in the thinning process, in one example, the method for thinning the flip chip on the circuit board further comprises the following steps:

adopt the multiple spot thickness measurement method, monitor the thickness at the attenuate in-process of treating attenuate flip chip, if the thickness of treating attenuate flip chip one side is greater than the thickness of opposite side, then adjustment unable adjustment base's angle to lift the big one side of treating attenuate flip chip thickness, then continue to grind or polish, guarantee that the treat attenuate flip chip thickness after the attenuate is even, thereby, guarantee that the surfacing and the attenuate thickness of flip chip attenuate are controllable.

The radiation test needs the comparison of test data before and after the chip is thinned, and in the prior art, before the thinning, the flip chip is welded and installed on a circuit board through a high-temperature welding process of more than 200 ℃, and then radiation test data acquisition and test verification are carried out. And then, detaching the circuit from the circuit board at high temperature, thinning the back of the flip chip, welding and mounting the circuit board by a high-temperature welding process at the temperature of more than 200 ℃, and performing a radiation test after thinning the chip. And comparing the radiation test results before and after thinning to obtain the radiation resistance level of the circuit. The thickness of the thinned chip is generally 30-100 micrometers, and the chip may be damaged by the action of high temperature of more than 200 ℃ for many times. Moreover, when the flip-chip packaged integrated circuit is welded on the upper plate, multiple steps of high-temperature reflow soldering process and the like are needed, which is not realized by welding of a single electric soldering iron in a common laboratory, so that test verification on a thinned field is impossible, a thinned sample needs to be brought back and subjected to the processes of welding the upper plate and the like, the possibility of stress damage to a thin chip is increased, and the efficiency of a radiation test is greatly influenced.

Therefore, the method for thinning the flip chip on the circuit board provided by the embodiments of the present application adopts the following steps: pasting the circuit board on the fixed base in a mode that the flip chip to be thinned on the circuit board is far away from the fixed base; pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; get rid of and grind the membrane, and paste polishing cloth on the grinding end face that grinds the drill bit, treat the back of attenuate flip chip and polish, the thickness of treating attenuate flip chip reaches preset polishing thickness, realize the direct attenuate of the flip chip of welding on the circuit board, reduce the number of times that will the flip chip follow circuit board dismantlement in the traditional technology, reduce many times high temperature welding technology to the thermal damage of flip chip, thereby guarantee that the performance of flip chip around the attenuate is not impaired, improve the experimental verification before and after the attenuate widely, the efficiency of radiation test, and the problem of flip chip radiation resistance test validity difference on the circuit board has been solved.

Furthermore, the flip chip can be thinned, and meanwhile, pins of the circuit are ensured to be intact and not damaged, namely, the electrical property is good, the requirement of applying an electrical bias condition in a radiation test is met, and the effectiveness of the radiation test is also ensured.

It should be understood that although the various steps in the flow charts of fig. 1-3 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1-3 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performance of the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternating with other steps or at least some of the sub-steps or stages of other steps.

In one embodiment, as shown in fig. 4 and 5, there is also provided a grinding drill for implementing a flip chip thinning method on a circuit board, comprising:

a first cylindrical structure 41, wherein a rectangular groove 411 is formed on the side wall of the first cylindrical structure 41;

a second cylindrical structure 43, the diameter of the second cylindrical structure 43 being greater than the diameter of the first cylindrical structure 41, a first end face of the second cylindrical structure 43 being mechanically connected to the first cylindrical structure 41, and a second end face of the second cylindrical structure 43 being an abrasive end face 431.

In one example, the first cylindrical structure is an iron structure, and the second cylindrical structure is an iron structure.

The grinding drill bit that this application provided is designed for flip-chip attenuate method on this application circuit board specially, and it can directly carry out local attenuate to flip-chip on the circuit board and do not harm peripheral paster electric capacity, through the method that coarsely grinds, grinds finely, throws the multistep and combine together, can attenuate flip-chip as required to suitable thickness to satisfy the thickness requirement of circuit radiation ability aassessment.

In one embodiment, as shown in fig. 6, there is also provided a mounting base for implementing a flip-chip thinning method on a circuit board, characterized by comprising a rectangular plate made of aluminum; a plurality of through holes for installation and fixation are formed in the aluminum rectangular plate.

It should be noted that the through hole is used for fixedly mounting the fixing base on the chip thinning platform.

The fixing base is specially designed for the method for thinning the flip chip on the circuit board, and can meet the fixing requirements of the printed circuit boards with various length and width sizes.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A method for thinning a flip chip on a circuit board is characterized by comprising the following steps:

the circuit board is pasted on the fixed base in a mode that the flip chip to be thinned on the circuit board is far away from the fixed base;

pasting a grinding film on the grinding end face of the grinding drill bit, and grinding the back face of the flip chip to be thinned until the thickness of the flip chip to be thinned reaches a preset grinding thickness; the grinding drill bit is a grinding drill bit with the diameter of the grinding end face corresponding to the width of the flip chip to be thinned;

get rid of grind the membrane, and paste polishing cloth on the grinding end face of grinding drill bit, it is right treat that attenuate flip chip's the back polishes, until treat that attenuate flip chip's thickness reaches and predetermines polishing thickness.

2. The method of flip chip thinning on a circuit board of claim 1,

paste on the grinding terminal surface that grinds the drill bit and grind the membrane, it is right treat that the back of attenuate flip chip grinds, until treat that the thickness of attenuate flip chip reaches the step of predetermineeing grinding thickness, include:

adhering a first-granularity grinding film on the grinding end face of the grinding drill bit, and performing coarse grinding on the back face of the flip chip to be thinned until a preset coarse grinding thickness is reached;

removing the first-granularity grinding film, adhering a second-granularity grinding film on the grinding end face of the grinding drill bit, and finely grinding the back face of the flip chip to be thinned until the preset grinding thickness is reached; the second grain size milled film has a grain size smaller than the grain size of the first grain size milled film.

3. The method of flip chip thinning on a circuit board of claim 2, wherein the first grain size ground film is a 45 micron grain size ground film.

4. The method of flip chip thinning on a circuit board of claim 2, wherein the second grain size ground film is a 30 micron grain size ground film.

5. The method of flip chip thinning on circuit board according to any one of claims 1 to 4,

get rid of grind the membrane, and paste polishing cloth on the grinding end face of grinding drill bit, it is right treat that attenuate flip chip's the back polishes, until treat that attenuate flip chip's thickness reaches the step of presetting polishing thickness, include:

removing the grinding film, adhering first polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned for a preset time under a first-granularity diamond suspension;

and removing the first polishing cloth, pasting a second polishing cloth on the grinding end face of the grinding drill bit, and polishing the back face of the flip chip to be thinned under the second-granularity diamond suspension until the preset polishing thickness is reached.

6. The method of thinning a flip chip on a circuit board of claim 5, wherein the first polishing cloth is a Kempad type polishing cloth; the first particle size diamond suspension is a 6 micron particle size diamond suspension.

7. The method of thinning a flip chip on a circuit board according to claim 5, wherein the second polishing cloth is Red Final C-type flocked cloth; the second particle size diamond suspension is a 1 micron particle size diamond suspension.

8. The method of thinning a flip chip on a circuit board of claim 5, wherein the predetermined time period is 60 seconds to 90 seconds.

9. A grinding drill bit for realizing a method for thinning a flip chip on a circuit board is characterized by comprising the following steps:

the side wall of the first cylindrical structure is provided with a rectangular groove;

the diameter of the second cylindrical structure is larger than that of the first cylindrical structure, the first end face of the second cylindrical structure is mechanically connected with the first cylindrical structure, and the second end face of the second cylindrical structure is a grinding end face.

10. A fixed base for realizing a method for thinning a flip chip on a circuit board is characterized by comprising an aluminum rectangular plate; a plurality of through holes for installation and fixation are formed in the aluminum rectangular plate.