Method for detecting silver paste coverage of post-plastic packaging product

Abstract

The present application relates to a kind of detection methods for the silver paste coverage of plastic package product, comprising the following steps: through high-temperature baking product, the adhesive between chip and cap is softened, then the product is opened by mechanical tool;Stereo microscope is used to take a photo of the chip after opening cap;According to the original product wiring diagram, combined with the photo of chip, the silver paste coverage is preliminarily judged by naked eye;Open AutoCAD software, copy the chip photo to the interface of AutoCAD, and calculate the total area S of chip and the area S1 of the part covered by silver paste, S1 divided by S obtains accurate silver paste coverage Q.The present application can accurately detect the silver paste coverage of product, eliminate the misjudgment of product as unqualified product, reduce the loss of company and waste of resources.

Description

TECHNICAL FIELD

[0001] The present application relates to silver paste coverage detection, in particular to a kind of detection method of silver paste coverage of product after plastic packaging. BACKGROUND

[0002] In the process of integrated circuit or separate device packaging, silver paste coverage is an important index of packaging die, and the silver paste coverage of the die of the general integrated circuit must reach more than 75%, and the silver paste coverage of the die of the integrated circuit or separate device with high conductivity requirement needs to meet the requirement of 90%, that is, the coverage requirement of 75% at least three edges is glued, and the four edges are glued. The principle process is that silver paste can cover the chip with sufficient area after solidification, so that the chip and the frame are combined firmly, higher thrust, better conductive path and better heat dissipation are formed.

[0003] In the die mounting process, since the silver paste is in liquid state when mounting the die, the silver paste still exists the phenomenon of climbing and overflowing in the subsequent solidification process. In the conventional case, when the glue is obviously covered to meet the requirement during die mounting, it is concluded without doubt that the requirement is met. However, since the silver paste is in a dynamic state during die mounting, especially when there are small air bubbles in the glue and the diameter of the glue needle gradually decreases over time, the silver paste glueing occurs in a critical state of coverage during die mounting. Therefore, it is impossible to measure the correct silver paste coverage by only detecting the un-solidified chip and glue after die mounting.

[0004] At present, X-ray is used to observe the silver paste coverage of the solidified product, but X-ray has a requirement for the thickness of the silver paste layer. When the thickness of the silver paste layer is thin, X-ray is easy to misjudge and determine the qualified product as unqualified product. Therefore, in order to improve the detection accuracy, chemical corrosion method is used to detect the silver paste coverage of the solidified product. After the product is corroded by chemical agent, the silver paste coverage of the product is observed by opening the cap. However, since the chemical corrosion agent has a corrosion effect on the solidified silver paste thin layer, the observed silver paste coverage is not the real result. Therefore, there is an urgent need for a method to accurately evaluate the silver paste coverage. SUMMARY

[0005] In order to overcome the above defects, the present application provides a kind of detection method of silver paste coverage of product after plastic packaging, which can accurately detect the silver paste coverage of product, prevent the product from being misjudged as unqualified product, and reduce the loss and waste of resources of company.

[0006] The technical scheme adopted by the present application to solve its technical problems is:

[0007] A kind of detection method of silver paste coverage of product after plastic packaging, comprising the following steps:

[0008] Step 1: take out the product, which includes the chip and the cap, the chip surface is covered with silver paste, the chip and the cap are bonded together by the adhesive, bake the product at high temperature of 420-450℃ for 3-10min, so that the adhesive between the chip and the cap softens, then use mechanical tools to clamp and destroy the product, so that the cap and the chip are separated;

[0009] Step 2: take a photo of the opened cap chip using a stereomicroscope to get an enlarged chip photo;

[0010] Step 3: according to the original product wiring diagram, combined with the chip photo, the silver paste coverage is preliminarily judged by the naked eye, if the silver paste covers the whole chip, it can be judged that the product is qualified, if there is an area of silver paste not covering the chip, go to step 4;

[0011] Step 4: open AutoCAD software, copy the chip photo into the AutoCAD interface, and calculate the total area S of the chip and the area S1 of the part covered by silver paste, S1 divided by S gets the accurate silver paste coverage Q.

[0012] Preferably, in step 1, the product is baked using a constant temperature heating table, the baking conditions are: baking temperature 425±5℃, baking time 6±1min, the cap of the baked product is clamped and shaken multiple times using pliers, so that the weak area of the combination of silver paste and adhesive in the product is separated, and the chip and the cap are separated from each other.

[0013] Preferably, in step 2, the magnification of the stereomicroscope is 50-60 times.

[0014] Preferably, step 4 includes the following steps:

[0015] (1) open AutoCAD software, copy the chip photo into the AutoCAD software interface;

[0016] (2) select the area measurement tool in AutoCAD software;

[0017] (3) select the entire surface of the chip according to the operation requirements, and get the total area of the chip, denoted as S;

[0018] (4) select the area of the silver paste covered region in the chip according to the operation requirements, and get the area of the part covered by silver paste in the chip, denoted as S1;

[0019] (5) divide S1 by S and multiply by 100%, get the silver paste coverage, denoted as Q;

[0020] (6) according to the Q value and combined with the product silver paste coverage index, to judge whether the product is qualified.

[0021] The beneficial effects of the present application are:

[0022] 1) The present application opens the product by high-temperature cap opening, that is, the adhesive between the chip and the cap is softened by high-temperature baking, and then a mechanical tool is used to clamp and destroy the product, so that the cap is separated from the chip, that is, the product is opened by a physical method, so that the silver paste layer on the chip is not damaged, which lays a foundation for accurate determination of the silver paste coverage rate;

[0023] 2) The present application first introduces AutoCAD to calculate the silver paste coverage rate, and the obtained silver paste coverage rate is very accurate, which overcomes the error of the silver paste coverage rate obtained by the previous method, and the result is more reliable and self-evident;

[0024] 3) The present application is simple to operate, and the obtained silver paste coverage rate is high, and the present application is particularly suitable for the case where there is a thin layer of silver paste in the chip, which overcomes the misjudgment of the silver paste coverage rate of the thin layer of silver paste product by X-ray alone, and avoids the corrosion misjudgment caused by the chemical corrosion cap opening method; By using the method combined with the X-ray detection method, the silver paste coverage of the product can be quickly determined, and the silver paste coverage rate of the product can be accurately detected, which eliminates the misjudgment of the product caused by the thin silver paste layer and reduces the loss and waste of resources of the company. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] A detection method for the silver paste coverage rate of a plastic encapsulated product, comprising the following steps:

[0027] Step 1: Take out the product, the product comprising a chip and a cap, the chip surface being covered with silver paste, the chip and the cap being bonded together by an adhesive, and placing the product in a high temperature of 420-450℃ for baking for 3-10min to soften the adhesive between the chip and the cap, and then clamping and destroying the product by a mechanical tool to separate the cap from the chip;

[0028] Step 2: Taking a photograph of the opened chip by a stereomicroscope to obtain an enlarged chip photo;

[0029] Step 3: According to the original product wiring diagram, combined with the chip photo, the silver paste coverage is preliminarily judged by naked eye, if the silver paste covers the chip completely, the product is judged as qualified product, if there is an area of the chip not covered by silver paste, step 4 is entered;

[0030] Step 4: Open AutoCAD software, copy the chip photo to the interface of AutoCAD, and calculate the total area S of the chip and the area S1 of the part of the chip covered by silver paste, and then S1 / S gives the accurate silver paste coverage Q.

[0031] In the present application, the method of high-temperature mechanical cap opening is used to open the chip with silver paste, and then the product is photographed by using a stereomicroscope, and the silver paste coverage is preliminarily confirmed by using the enlarged chip photo and combining the product wiring diagram by naked eye, if the chip is completely covered by silver paste, the product is judged as qualified product, if there is an area of the chip not covered by silver paste, AutoCAD software is used to accurately calculate the silver paste coverage of the chip. The present application is simple to operate, and the obtained silver paste coverage has high precision, the present application is particularly suitable for the case that there is a thin layer of silver paste in the chip, and the misjudgment of the silver paste coverage of the product caused by X-ray is overcome, and the corrosion misjudgment caused by the corrosion cap opening method is also avoided; the AutoCAD is introduced in the present application to calculate the silver paste coverage, the obtained silver paste coverage is very accurate, the error of the silver paste coverage obtained by the previous method is overcome, and the result is more reliable and self-evident. A large number of products determined as unqualified products by the conventional method exist in the chip production enterprise, a large number of products determined as unqualified products by X-ray exist in the company, and the qualified rate of the products after testing by the present application reaches more than 99%, thereby the economic loss of the company is recovered, the waste of resources is reduced, and the present application has very strong practicability.

[0032] In step 1, the product is baked by using a constant temperature heating table, the baking condition is that the baking temperature is 425±5℃, the baking time is 6±1min, the cap of the baked product is clamped by using a forceps and shaken for multiple times, so that the weak area of the silver paste combined with the adhesive is separated, and the chip and the cap are separated from each other. The principle of high-temperature mechanical cap opening is as follows: the chip is bonded to the cap by the adhesive, the adhesive is epoxy resin, the epoxy resin is an organic matter, and the epoxy resin will soften in a high-temperature state, so the bonding force of the epoxy resin will be weakened, and then the cap is clamped by using a forceps, so that the cap is separated from the chip, that is, the product is opened by using a physical method in the present application, and the silver paste layer on the chip is not damaged, which lays a foundation for accurately determining the silver paste coverage.

[0033] In step 2, the magnification of the stereomicroscope is 50-60 times. The enlarged chip photo obtained by using the microscope is beneficial to naked eye observation and accurate area calculation by using AutoCAD software.

[0034] Wherein, step 4 comprises the following steps:

[0035] (1) open AutoCAD software, copy the chip photo to the interface of AutoCAD software;

[0036] (2) select the area measurement tool in AutoCAD software;

[0037] (3) select the entire surface of the chip according to the operation requirement, and obtain the total area of the chip, denoted as S;

[0038] (4) select the area covered by silver paste in the chip according to the operation requirement, and obtain the area of the part covered by silver paste in the chip, denoted as S1;

[0039] (5) divide S1 by S and multiply by 100%, to obtain the silver paste coverage, denoted as Q;

[0040] (6) according to the Q value and combined with the index of product silver paste coverage, to judge whether the product is qualified. When the product is an integrated circuit or a separate device with high conductivity requirement, the silver paste coverage needs to reach more than 90%, if the silver paste coverage Q value obtained by the detection method is greater than 90%, the product is a qualified product, otherwise it is an unqualified product; when the product is a general integrated circuit, the silver paste coverage needs to reach more than 75%, if the silver paste coverage Q value obtained by the detection method is greater than 75%, the product is a qualified product, otherwise it is an unqualified product. Specific embodiments:

[0042] Step 1: take out the chip product, which has been tested by X-ray and the silver paste coverage is about 75%, place the product in high temperature of 420℃ for 5min, then use pliers to clamp and damage the product, so that the cap and the chip are separated;

[0043] Step 2: use 50 times stereoscopic microscope to take a photo of the chip after opening the cap, to obtain the enlarged chip photo;

[0044] Step 3: according to the original chip wiring diagram, combined with the chip photo, the naked eye preliminarily judges that there is a silver paste uncovered area in the chip;

[0045] Step 4: use AutoCAD software to accurately calculate the silver paste coverage

[0046] (1) open AutoCAD software, copy the chip photo to the section of AutoCAD software;

[0047] (2) select the area measurement tool in AutoCAD software;

[0048] (3) According to the operation requirement, the whole surface of the chip is selected, and the total area S of the chip is obtained, S is 49.4332;

[0049] (4) According to the operation requirement, the area of the chip covered by the silver paste is selected, and the area S1 of the chip covered by the silver paste is obtained, S1 is 49.2712;

[0050] (5) S1 is divided by S and multiplied by 100%, and the silver paste coverage rate Q is obtained as 99.67%;

[0051] (6) The index of the silver paste coverage rate of the product is greater than 90%, and the actual silver paste coverage rate of the product obtained is 99.67%, so the product is a qualified product.

[0052] Through the method, the products determined as unqualified by X-ray examination are observed, and such products are caused by misjudgment due to too thin silver paste coverage, so X-ray cannot truly show the silver paste coverage of the product. Therefore, the silver paste coverage area of the product can be quickly detected by X-ray, when the X-ray detection method determines that the product is qualified, it is determined that the product is qualified, if the product is determined as unqualified by the X-ray detection method, similar products are detected by the method, and the silver paste coverage rate of the product is accurately detected, if the method determines that the product is qualified, it is determined that the product is finally qualified, if the method determines that the product is unqualified, it is determined that the product is finally unqualified. Therefore, by using the method combined with the X-ray detection method, the silver paste coverage of the product can be quickly determined, and the silver paste coverage rate of the product can be accurately detected, so that the misjudgment of the product caused by the thin silver paste layer is avoided, and the loss and resource waste of the company are reduced.

[0053] It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for detecting the silver paste coverage of a product after molding, characterized in that: It comprises the following steps: Step 1: take out the product, which comprises a chip and a cap, the surface of the chip is covered with silver paste, the chip and the cap are bonded together by an adhesive, and the product is baked at a high temperature of 420-450 DEG C for 3-10 min, so that the adhesive between the chip and the cap is softened, and then the product is clamped and destroyed by a mechanical tool, so that the cap is separated from the chip; Step 2: take a photo of the chip after opening the cap by using a stereomicroscope, and obtain an enlarged chip photo; Step 3: according to the original product wiring diagram, combined with the chip photo, the silver paste coverage condition is preliminarily judged by naked eye, if the silver paste covers the whole chip, it can be judged that the product is qualified, if there is an area of the chip not covered by silver paste, it enters step 4; Step 4: open AutoCAD software, copy the chip photo into the interface of AutoCAD, and calculate the total area S of the chip and the area S1 of the part of the chip covered by silver paste, S1 divided by S obtains the accurate silver paste coverage rate Q; In step 1, the cap of the baked product is clamped by a pair of pliers and shaken several times, so that the weak area of the combination of silver paste and adhesive in the product is separated, and the chip and the cap are separated from each other; Step 4 comprises the following steps: (1) open AutoCAD software, copy the chip photo into the interface of AutoCAD software; (2) select the area measurement tool in AutoCAD software; (3) select the entire surface of the chip according to the operation requirement, and obtain the total area of the chip, denoted as S; (4) select the area of the silver paste covered region in the chip according to the operation requirement, and obtain the area of the part of the chip covered by silver paste, denoted as S1; (5) divide S1 by S and multiply by 100%, to obtain the silver paste coverage rate, denoted as Q; (6) according to the Q value and combined with the product silver paste coverage rate index, to judge whether the product is qualified.

2. The method of claim 1, wherein the method is characterized by: In step 1, the product is baked by using a constant temperature heating table, and the baking conditions are as follows: baking temperature 425±5 DEG C, baking time 6±1 min.

3. The method of claim 1, wherein the method is characterized by: In step 2, the magnification of the stereomicroscope is 50-60 times.