Flip chip dedicated solder mark inspection tool

Abstract

This application relates to a solder mark inspection tool specifically for flip-chip devices, comprising: a body and an adhesive material. The body has a central hole adapted to the outer contour of the chip to be inspected. The lower part of the body contacts the packaging substrate, and the outer contour of the lower part of the body is smaller than the outer contour of the packaging substrate. The adhesive material is used to uniformly adhere to the upper surfaces of the chip and the body, providing upward tension to the chip. This application inspects the solder assembly of the chip and packaging substrate after reflow soldering and before the encapsulation process. The solder mark inspection tool extends the bonding area of ​​the adhesive material, enhances the bonding strength, balances the force on the chip surface, and ensures that the chip will not break when pulled out. It is particularly suitable for use with small and thin chips, and can also prevent residual adhesive or foreign matter from mixing between the chip and the packaging substrate during the inspection process, affecting the inspection results.

Description

Technical Field

[0001] This application relates to the field of integrated circuit packaging technology, and in particular to a special tool for inspecting solder marks on flip-chips. Background Technology

[0002] Flip-chip (FC) packaging is a technology that interconnects a chip with its functional areas facing down, away from the packaging substrate, using solder bumps (or simply bumps). Flip-chip packaging typically uses planar processes to create lead-free solder joints at the input / output (I / O) terminals of the integrated circuit chip. These solder joints on the chip are then aligned and mounted with the pads on the packaging substrate. A solder reflow process is then used to form solder balls between the chip and the substrate pads. Finally, underfill adhesive is filled into the gaps between the chip and the substrate, ultimately achieving electrical, thermal, and mechanical connections between the chip and the packaging substrate.

[0003] After the underfill is completed, the assembled components usually need to be inspected non-destructively using equipment such as optical microscopes or X-ray inspection machines to detect defects such as solder joint bridging / open circuits, misalignment, poor solder joint wetting, solder joint voids / bubbles, solder joint cracks / brittleness, and chip breakage.

[0004] However, since traditional non-destructive inspection is usually carried out after the bottom filler adhesive is applied, once a defect is found during inspection, a large number of chips have already been scrapped. In order to prevent process deviation during manufacturing and cause poor product soldering, this application proposes an online inspection tool for soldering marks. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the prior art and propose a tool for inspecting solder marks on flip-chips, which can disassemble the flip-chip and the packaging substrate to observe the soldering condition.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] This application provides a special solder mark inspection tool for flip-chip. The tool includes a body and an adhesive material. The body has a central hole that matches the outer contour of the chip to be inspected. The lower part of the body is in contact with the packaging substrate, and the outer contour of the lower part of the body is smaller than the outer contour of the packaging substrate. The adhesive material is used to uniformly adhere to the chip and the upper surface of the body and to provide an upward pulling force to the chip.

[0008] The solder mark inspection tool of this application has a central hole for placing a chip. The main body of the tool surrounds the outside of the chip, which can increase the bonding area of ​​the adhesive, enhance the bonding strength, balance the stress on the chip (preventing chip breakage), prevent adhesive from mixing in, and make the solder mark inspection more accurate.

[0009] In one possible implementation, the upper part of the body has an adhesive surface for bonding adhesive material, the area of ​​which is greater than or equal to the area of ​​the chip in a ratio of 2:1.

[0010] In one possible implementation, the adhesive surface is 0.5-2 mm above the upper surface of the chip.

[0011] In one possible implementation, the adhesive surface is provided with a grid-like microgroove.

[0012] In one possible implementation, the main body is rectangular and includes four side walls that connect end to end.

[0013] In one possible implementation, the main body is made of steel.

[0014] In one possible implementation, the main body is 10-15mm long, 8-13mm wide, 0.5-2mm high, and 0.5-2mm thick.

[0015] In one possible implementation, the adhesive material is a flowable two-component adhesive material.

[0016] The welding mark inspection method used in this application includes:

[0017] In the installation process, the solder mark inspection tool is used to fix the chip to be tested, so that the chip part is inserted into the center hole of the main body, and the lower surface of the main body is in contact with the packaging substrate.

[0018] Apply adhesive: Apply adhesive to the bonding surface of the main body to ensure that the adhesive material is fully bonded and in contact with the main body and the upper surface of the chip.

[0019] The curing process cures the adhesive material.

[0020] In the separation process, the packaging substrate is fixed, and the adhesive material is peeled off, so that the adhesive material, together with the main body and the chip, is separated from the packaging substrate.

[0021] The inspection process involves using an optical microscope to inspect the bonding areas of the chip and / or packaging substrate for solder marks.

[0022] In one possible implementation, the weld trace inspection includes one or more of the following: whether there are foreign objects, whether there are incomplete welds, and whether there are air bubbles.

[0023] In one possible implementation, the inspection method involves inspecting the flip-chip after reflow soldering and before the encapsulation process begins.

[0024] The solder joint inspection tool of this application can periodically perform destructive inspections on reflow soldered chip assemblies, separating the chip and the packaging substrate to directly inspect the solder joints. This application can be applied to small-sized, thin-thick chips, avoiding situations where the adhesive bonding area is too small for the chip to be easily removed, uneven chip stress leading to breakage, or adhesive material mixed between the chip and the packaging substrate, making it impossible to accurately determine solder joint defects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a flip-chip structure;

[0026] Figure 2 This is a top view of the welding trace inspection tool of this application;

[0027] Figure 3 for Figure 2 Cross-sectional view along the middle AA.

[0028] The components are: 1. Underfill adhesive; 2. Bottom solder pad metal; 3. Chip; 4. Solder ball; 5. Passivation material; 6. Solder mask; 7. Packaging substrate; 8. Contact pad; 9. Body; 10. Adhesive material. Detailed Implementation

[0029] To illustrate the technical content, structural features, achieved objectives, and effects of this application in detail, the technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. In the following description, for illustrative purposes, numerous specific details are set forth to provide a detailed description of various exemplary embodiments or implementations of the invention. However, various exemplary embodiments may also be implemented independently without these specific details or in one or more equivalent arrangements. Furthermore, the various exemplary embodiments may differ, but are not necessarily exclusive. For example, the specific shape, structure, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0030] Figure 1 This is a schematic diagram of a flip chip structure, including a chip 3, a packaging substrate 7, and several solder balls 4 connecting the chip 3 and the packaging substrate 7. The chip 3 has several bottom solder pads 2 on its electrical connection surface, and the packaging substrate 7 has several contact pads 8 on its upper surface. The chip 3 is flip-chip connected to the packaging substrate 7 via solder balls.

[0031] The flip-chip soldering trace inspection tool of this application is used to inspect the soldering assembly of the chip and the packaging substrate after reflow soldering and before the encapsulation process.

[0032] See Figure 2-3 A tool for inspecting solder marks on flip-chip devices includes a body 9 and an adhesive material 10. The body 9 has a central hole that matches the outer contour of the chip 3 to be inspected. Typically, this central hole is square or rectangular. The central hole is designed to be slightly larger than the chip, and the gap between the central hole and the chip is less than or equal to 30µm ± 5µm.

[0033] When the solder joint inspection tool is in operation, the lower part of the main body 9 contacts the packaging substrate 7, and the outer contour of the main body 9 is smaller than the outer contour of the flip-chip packaging substrate 7. Therefore, when performing solder joint inspection, as long as the flip-chip packaging substrate 7 is fixed, a vertically upward force is applied to the main body 9 and the chip 3, the chip 3 and the packaging substrate 7 can be separated, thereby allowing inspection of the solder joint.

[0034] In one embodiment, the main body 9 is made of steel.

[0035] In one embodiment, the main body 9 is rectangular, comprising four end-to-end sidewalls. The main body is 13mm long, 11.5mm wide, 1mm high, and 1mm thick.

[0036] The function of the adhesive material 10 is to uniformly adhere to the upper surfaces of the chip 3 and the main body 9, and to provide the chip 3 with a pulling force away from the packaging substrate 7. In one embodiment of this application, the adhesive material 10 is a flowable adhesive (such as AB glue, using a commercially available two-component adhesive). When using it, the adhesive material is evenly spread on the upper surfaces of the main body and the chip to ensure that the force is evenly distributed on each part. After the adhesive material is spread, it is cured by means of static placement, light exposure, or heating. Then, force is applied to the adhesive material to separate the chip from the packaging substrate.

[0037] To improve adhesion, the upper part of the main body 9 has an adhesive surface for bonding the adhesive material 10, and the area of ​​the adhesive surface is in a 2:1 ratio to the area of ​​the chip.

[0038] In one embodiment, the adhesive surface may be 0.5-2 mm higher than the upper surface of the chip, which ensures that the chip separates from the packaging substrate when the main body is separated from the packaging substrate.

[0039] In one embodiment, the adhesive surface is further provided with a grid-like microgroove, the depth of which is 3-5 μm. The grid microgroove structure can optimize the stress distribution of the adhesive material, avoid chip damage, and improve the adhesion.

[0040] When inspecting flip-chips for solder marks using the aforementioned inspection tools, the following steps are included:

[0041] In the installation process, the solder mark inspection tool is used to fix the chip to be tested, so that the chip 3 is stuck in the center hole of the body 9 and the lower surface of the body 9 is in contact with the packaging substrate 7.

[0042] Apply the adhesive material evenly to the adhesive surface of the main body 9 and the upper surface of the chip 3, ensuring that the adhesive material is fully bonded and in contact with the main body 9 and the upper surface of the chip 3, without any air bubbles or omissions.

[0043] Allow the adhesive to cure for 15-30 minutes, until the adhesive reaches its optimal adhesion strength.

[0044] In the separation process, the packaging substrate 7 is fixed and the adhesive material is peeled off vertically upward at a constant speed, so that the adhesive material, together with the main body 9 and the chip 3, is separated from the packaging substrate 7.

[0045] The inspection process involves using an optical microscope or other inspection instruments to check for solder marks at the junction of chip 3 and / or packaging substrate 7. The inspection tool can be laid out according to the packaging substrate to inspect multiple chips sequentially.

[0046] The inspection of soldering marks includes checking for foreign objects between the chip and the packaging substrate, whether there are poor solder joints, and whether there are air bubbles, etc.

[0047] When inspecting solder joints, directly using adhesive to bond and separate chips can lead to problems, especially with small and thin chips. These issues include insufficient adhesive area resulting in weak bonding strength, uneven chip stress causing breakage, and adhesive residue becoming trapped between the chip and the packaging substrate, making the results unreliable. The solder joint inspection tool of this application extends the adhesive area, enhancing bonding strength and balancing the force on the chip surface, ensuring the chip won't break when pulled out. This makes it particularly suitable for small and thin chips. Furthermore, because the tool's main body surrounds the chip, it prevents adhesive or other foreign matter from becoming trapped between the chip and the packaging substrate, thus preventing solder joint marks from being covered and unreliable, and ultimately affecting the inspection results.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope of the invention. The scope of protection claimed by this application is defined by the appended claims, specification, and their equivalents.

Claims

1. A flip chip dedicated solder mark inspection tool characterized by, The tool includes a body and an adhesive material. The body has a central hole that matches the outer contour of the chip to be tested. The lower part of the body is in contact with the packaging substrate, and the outer contour of the lower part of the body is smaller than the outer contour of the packaging substrate. The adhesive material is used to evenly adhere to the chip and the upper surface of the body and to provide an upward pulling force to the chip.

2. The flip chip dedicated solder joint inspection tool of claim 1, wherein, The upper part of the main body has an adhesive surface for bonding adhesive material, and the area of ​​the adhesive surface is greater than or equal to the area of ​​the chip by a ratio of 2:

1.

3. The flip chip dedicated solder mark inspection tool of claim 2, wherein, The adhesive surface is 0.5-2mm higher than the upper surface of the chip.

4. The flip chip dedicated land inspection tool of claim 2, wherein: The adhesive surface is provided with a grid-like microgroove.

5. The flip chip dedicated land inspection tool of claim 1, wherein: The main body is rectangular and includes four side walls that connect end to end.

6. The flip chip dedicated land inspection tool of claim 1, wherein: The main body is made of steel.

7. The flip chip dedicated solder mark inspection tool of claim 1, wherein: The main body is 10-15mm long, 8-13mm wide, 0.5-2mm high, and 0.5-2mm thick.

8. The flip chip dedicated land inspection tool of claim 1, wherein: The adhesive material is a free-flowing two-component adhesive material.

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