Metal radiating fin removal test method applied to flip component

Abstract

The invention discloses a metal radiating fin removal test method applied to a flip component, which comprises the following steps: confirming the position and structural characteristics of an internal chip through X-ray characterization in advance, and based on an X-ray characterization result, etching metal on the surface layer of a radiating fin in an area right above the chip by adopting laser. And removing the deep metal which is not etched by the laser in a mechanical fixed-point grinding mode to form a groove. And a specific chemical reagent is used, and a high-temperature heating corrosion and infiltration stripping mode is adopted, so that residual metal and adhesive are removed. And finally, stripping the residual area of the residual radiating fin by adopting a mechanical stripping mode to realize complete removal of the metal radiating fin of the flip chip. The method can effectively avoid damage of an internal chip caused by external stress in the process of removing the metal cooling fin of the flip component, guarantees the completeness of the functional performance after the metal cooling fin of the component is removed, facilitates the smooth proceeding of a subsequent reliability test, and provides powerful support for failure analysis, fault positioning and mechanism analysis of the flip component.

Description

Technical Field

[0001] The present invention relates to the technical field of reliability and failure analysis, and particularly to a method for removing a metal heat sink applied to flip-chip components. Background Art

[0002] With the rapid development of emerging fields such as 5G communication, artificial intelligence, and the Internet of Things, the demand for flip-chip components with metal heat sinks continues to grow. Consequently, the demand for reliability evaluation and failure analysis of flip-chip components has gradually increased, inevitably involving the technical method of removing the metal heat sink of flip-chip components.

[0003] The metal heat sink of flip-chip components is usually tightly connected to the chip by means of welding, adhesives, or mechanical fixation. For conventional physical removal methods of metal heat sinks, it is difficult to accurately control the force, and it is easy to cause chip cracking or internal connection damage due to excessive force. If directly removed by chemical corrosion, it is difficult for chemical reagents to penetrate into the tiny gaps between the heat sink and the chip or inside the encapsulation material, and excessive chemical reagents are extremely likely to spread to the substrate or encapsulation body, causing corrosion damage and unable to guarantee the integrity of the functional performance after the metal heat sink is removed.

[0004] Therefore, it is very necessary and crucial to invent a method for removing a metal heat sink that can effectively avoid damage to the internal chip caused by external stress during the removal of the metal heat sink of flip-chip components, ensure the integrity of the functional performance after the metal heat sink of the component is removed, and contribute to the smooth progress of subsequent reliability tests. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for removing a metal heat sink applied to flip-chip components to solve the problems in the background art.

[0006] To solve the above technical problems, the present invention provides a method for removing a metal heat sink applied to flip-chip components, including the following steps:

[0007] Step 1: Confirm the position and structural characteristics of the internal chip through X-ray characterization;

[0008] Step 2: Based on the characterization result of Step 1, use laser etching to remove the surface metal of the heat sink in the area directly above the chip;

[0009] Step 3: Remove part of the deep metal that has not been laser-etched by mechanical fixed-point grinding to form a groove;

[0010] Step 4: Use chemical reagents and adopt the methods of high-temperature heating corrosion and infiltration peeling to remove the remaining metal and adhesive;

[0011] Step 5: Adopt the method of mechanical peeling to peel the remaining heat sink residual area, so as to completely remove the flip-chip metal heat sink.

[0012] In one embodiment, in the said Step 1, the structural features are confirmed by X-ray characterization to identify the structural shape of the heat sink, estimate the thickness dimension of the heat sink, and understand the bonding state between the heat sink and the internal chip.

[0013] In one embodiment, in the said Step 1, the component is scanned in the X / Y / Z three axial directions by X-ray characterization, and the internal chip position area is magnified by a sufficient magnification to clearly detect and identify the boundary of the internal chip.

[0014] In one embodiment, in the said Step 2, the laser etching area should be located directly above the internal chip, and the etching area range should cover the entire boundary of the internal chip; when the surface metal is completely etched, the deep metal is completely exposed, and the laser etching stops when the effect is no longer obvious during the re-laser etching.

[0015] In one embodiment, in the said Step 2, the laser etching should use infrared light waves, and the wavelength range is required to be not less than 1064 nm.

[0016] In one embodiment, in the said Step 3, the mechanical fixed-point grinding is realized by using an electric grinding pen to polish the area, and the rotation speed is controlled between 5000 and 16000 r / min; the depth of the formed groove does not exceed 2 / 3 of the estimated heat sink thickness dimension.

[0017] In one embodiment, the said Step 4 includes the following sub-steps:

[0018] Sub-step one, use dilute nitric acid chemical reagent, after high-temperature heating, corrode and remove the remaining metal;

[0019] Sub-step two, use acetone chemical reagent, after infiltration cleaning, manually peel the bonding glue.

[0020] In one embodiment, in the said sub-step one, the mass fraction of the dilute nitric acid concentration of the chemical reagent is required to be between 55% and 65%, and the high-temperature heating temperature is required to be between 100°C and 150°C; the completely heated dilute nitric acid should be gradually dropped into the groove to corrode and remove the remaining metal.

[0021] In one embodiment, in the said sub-step two, the grade of the acetone chemical reagent is not less than UL grade 99.8%, and the infiltration cleaning time shall not be less than 2 hours; after infiltration cleaning, use a cotton swab or tweezers to manually and slowly peel the bonding glue.

[0022] In one embodiment, in step 5, an industrial scalpel is used to pry the heat sink by increasing the torsion angle step by step along the edge gaps at the four corners of the metal heat sink. The scalpel blade is twisted at a small angle multiple times, and force is applied slowly and gradually to gradually increase the torsion angle and pry the heat sink, and then the remaining main body of the heat sink is mechanically peeled off.

[0023] The present invention provides a method for removing a metal heat sink applied to a flip-chip component, and the beneficial effects are as follows:

[0024] (1) By using the method of pre-local laser opening and chemical etching to remove the metal heat sink directly above the chip inside the flip-chip component, the risk of substrate damage or chip breakage caused by mechanical removal can be effectively avoided;

[0025] (2) After manufacturing a groove with a certain depth by mechanical fixed-point grinding and then performing chemical etching, the corrosion damage to the substrate, internal chip, and solder balls caused by the acid flow can be effectively prevented;

[0026] (3) By heating dilute nitric acid, the metal corrosion efficiency can be effectively improved; at the same time, the thermal stress damage caused by directly heating the component itself can be effectively reduced;

[0027] (4) For the removal of the metal heat sink of the flip-chip component, the external overstress during the process is effectively controlled, which can ensure the integrity of the function and performance of the component after the metal heat sink is removed, and effectively support the smooth progress of the subsequent reliability test;

[0028] (5) By using X-ray for structural positioning and further using the methods of local etching and acid etching, it can be effectively applied to products of other package types to achieve fixed-point opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic cross-sectional structure diagram of a flip-chip component with a metal heat sink according to the present invention.

[0030] Figure 2 For It is a schematic flow diagram of a method for removing a metal heat sink applied to a flip-chip component proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following further describes in detail a method for removing a metal heat sink applied to a flip-chip component proposed by the present invention with reference to the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise scales, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0032] The present invention provides a method for removing a metal heat sink applied to a flip-chip component, which is applied to, for example Figure 1Removal of the metal heat sink of the typical structural component shown.

[0033] Figure 1 It is a cross-sectional structure of a flip-chip component with a metal heat sink, mainly including: metal heat sink 1, adhesive 2, internal chip 3, microbumps 4, substrate 5, solder balls 6.

[0034] The method flow of the present invention is as Figure 2 shown, mainly including the following steps:

[0035] Step 1: Through X-ray characterization, confirm the position and structural characteristics of the internal chip;

[0036] Step 2: Based on the characterization result of Step 1, use laser etching to remove the surface metal of the heat sink in the area directly above the chip;

[0037] Step 3: By means of mechanical fixed-point grinding, remove part of the deep metal that has not been laser-etched to form a groove similar to a container;

[0038] Step 4: Use a specific chemical reagent with a certain concentration, and adopt the methods of high-temperature heating corrosion and infiltration stripping to remove the remaining metal and adhesive;

[0039] Step 5: Adopt the method of mechanical stripping to strip the remaining heat sink residual area, realizing the complete removal of the metal heat sink of the flip chip.

[0040] In Step 1, the position area of the internal chip should be magnified by a sufficient magnification to clearly detect the boundary of the internal chip, providing a basis for the selection of the subsequent laser etching area.

[0041] In Step 2, the laser etching area should be located directly above the internal chip, and the etching area range should cover the entire boundary of the internal chip;

[0042] After part of the surface metal is etched, to avoid or reduce the impact of the laser on the internal chip, the laser energy level can be lowered and the etching can continue;

[0043] When the deep metal is completely exposed and the effect is not obvious when laser etching is performed again, the laser etching stops.

[0044] In Step 3, part of the deep metal is removed by means of mechanical fixed-point grinding to form a groove similar to a container, and the depth of the groove should not exceed 2 / 3 of the estimated heat sink thickness dimension; the purpose is to prevent the mechanical stress from damaging the internal chip due to the excessive depth of the groove.

[0045] In Step 4, dilute nitric acid with a mass fraction required to be between 55% and 65% is used and heated to 100°C to 150°C at high temperature;

[0046] Gradually drop the heated dilute nitric acid solution into the groove to corrode and remove the remaining metal. Note that the added amount should not overflow the groove formed in Step 3.

[0047] Specifically, observe the metal corrosion situation every 3 - 5 minutes. When the remaining metal in the groove is completely corroded or the inner chip boundary is completely exposed, stop the acid corrosion and wash it with deionized water.

[0048] After washing 2 - 3 times, use an acetone reagent with a chemical grade not lower than 99.8% of UL level to soak and wash for more than 2 hours.

[0049] After the bonding glue is softened enough, use a cotton swab or tweezers to manually and slowly peel off the bonding glue.

[0050] In Step 5, mechanically peel off the remaining heat sink body. Specifically, use a blade to cut into any side from the top corner of the device, and by twisting the blade surface at a small angle multiple times, apply force slowly and gradually, and gradually increase the twisting angle to pry the heat sink, so that the gap between the heat sink and the substrate becomes larger, and then perform the same operation on the other three sides in turn.

[0051] It should be particularly noted that during the operation process, do not forcibly twist or turn the blade surface, and the force should be applied gently and gradually. The separation degree between the heat sink and the substrate should be gradually increased by prying multiple times, and do not pry it open violently at one time, and do not pry it at one top corner or one side for a long time. Continuously repeat this process until the remaining main body of the heat sink completely falls off.

[0052] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure are within the protection scope of the claims.

Claims

1. A metal heat sink removal test method for flip-chip components, characterized in that: The following steps are involved: Step 1: Confirm the internal chip position and structural features through X-ray characterization; Step 2: Based on the characterization results of step 1, use laser to etch away the surface metal of the heat sink directly above the chip; Step 3: Remove some of the deep metal that has not been laser-etched by mechanical fixed-point grinding to form a groove; Step 4: Use chemical reagents to remove the remaining metal and adhesive by high temperature heating corrosion and immersion stripping; Step 5: Use mechanical peeling to peel off the remaining heat sink residue area to completely remove the flip chip metal heat sink.

2. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: In step 1, the structural features are confirmed by X-ray characterization, the structural shape of the heat sink is identified, the thickness of the heat sink is estimated, and the bonding state between the heat sink and the internal chip is understood.

3. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: In step 1, the components are scanned in three axes of X / Y / Z by X-ray characterization, and the internal chip position area is magnified sufficiently to clearly detect and identify the internal chip boundary.

4. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: In step 2, the laser etching area should be located directly above the internal chip, and the etching area should cover the entire boundary of the internal chip; when the surface metal is completely etched, the deep metal is completely exposed, and the effect of laser etching is no longer obvious when it is performed again, the laser etching is stopped.

5. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: In step 2, the laser etching should use infrared light waves, and the wavelength range is required to be no less than 1064nm.

6. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: In step 3, mechanical fixed-point grinding is achieved by regional grinding with an electric grinder, and the rotation speed is controlled between 5000 and 16000 r / min; the depth of the groove formed does not exceed 2 / 3 of the estimated heat sink thickness.

7. The metal heat sink removal test method for flip-chip components as claimed in claim 1, characterized in that: The step 4 includes the following sub-steps: Sub-step 1, using dilute nitric acid as a chemical reagent, heating at high temperature, and corroding and removing the remaining metal; Sub-step 2: Use acetone chemical reagent to soak and clean, and then manually peel off the adhesive.

8. The test method for removing the metal heat sink applied to flip-chip components according to claim 7 is characterized in that: In the sub-step 1, the concentration of the chemical reagent dilute nitric acid is required to be between 55% and 65%, and the high-temperature heating temperature is required to be between 100° C. and 150° C.; the completely heated dilute nitric acid should be gradually dripped into the groove to corrode and remove the remaining metal.

9. The test method for removing the metal heat sink applied to flip-chip components according to claim 7, characterized in that: In the sub-step 2, the grade of the acetone chemical reagent is not less than UL grade 99.8%, and the immersion cleaning time is not less than 2 hours; after the immersion cleaning, use a cotton swab or tweezers to manually and slowly peel off the adhesive.

10. The test method for removing the metal heat sink of flip-chip components according to claim 1, characterized in that: In step 5, an industrial scalpel is used to pry the heat sink along the gaps at the four corners of the metal heat sink by twisting the blade at a small angle multiple times, slowly and gradually applying force, gradually increasing the twisting angle, and mechanically peeling off the remaining heat sink body.

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