Stress measurement method

Abstract

The application provides a stress measurement method for measuring warping stress of a package, the package comprising a bonding surface and a warping surface, the warping surface being arranged opposite to the bonding surface, characterized in that the stress measurement method comprises: placing the package on a horizontal surface, a gap being formed between the bonding surface and the horizontal surface; placing a counterweight at the center of the warping surface of the package, so that the bonding surface moves towards the horizontal surface; judging whether the bonding surface of the package is bonded to the horizontal surface; and when judging that the bonding surface of the package is bonded to the horizontal surface, obtaining the warping stress according to the weight of the counterweight. The application indirectly obtains the warping stress of the package by measuring the pressure applied on the package by using the relationship between the acting force and the counteracting force, and the measurement method is simple and can obtain the specific value of the warping stress without using special equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor packaging, and in particular to a stress measurement method. BACKGROUND

[0002] In the process of packaging a chip, multiple reflow soldering and cooling are required. Due to the mismatch of the coefficient of thermal expansion (CTE) of the packaging material, the package will experience inconsistent expansion and contraction after experiencing temperature changes, resulting in warpage stress and causing the package to warp. The size of the warpage stress will directly affect the subsequent process handling and reliability of the package. When it exceeds a certain limit, the subsequent process cannot be performed. The existing warpage stress measurement method requires the use of special equipment for measurement, which is relatively complex and costly. Alternatively, it relies on indirect measurement of the warpage height of the package. This method cannot accurately determine the size of the warpage stress and is not precise enough. SUMMARY

[0003] Therefore, it is necessary to provide a stress measurement method that can simply and accurately measure the warpage stress of a package.

[0004] The present application provides a stress measurement method for measuring the warpage stress of a package. The package includes a bonding surface and a warpage surface. The warpage surface is arranged opposite to the bonding surface. The stress measurement method includes: placing the package on a horizontal surface, forming a gap between the bonding surface and the horizontal surface; placing a counterweight at the center of the warpage surface of the package to move the bonding surface towards the horizontal surface; determining whether the bonding surface of the package is in contact with the horizontal surface; and when it is determined that the bonding surface of the package is in contact with the horizontal surface, obtaining the warpage stress according to the weight of the counterweight.

[0005] Optionally, the counterweight includes a plurality of counterweight pieces. The step of placing a counterweight at the center of the warpage surface of the package to move the bonding surface towards the horizontal surface includes: placing the counterweight pieces in order from large to small according to their weights, so that the bonding surface of the package is in contact with the horizontal surface.

[0006] Optionally, the step of judging whether the fitting surface of the packaging piece fits the horizontal plane comprises: measuring the size of the gap between the fitting surface of the packaging piece and the horizontal plane by using a measuring piece; judging whether the gap is less than or equal to a target value; when judging that the gap is less than or equal to the target value, judging that the packaging piece fits the horizontal plane; and when judging that the gap is greater than the target value, judging that the packaging piece does not fit the horizontal plane, and continuing to perform the step of placing a counterweight at the center of the warped surface of the packaging piece to move the fitting surface towards the horizontal plane.

[0007] Optionally, the measuring piece is a plug gauge, and whether the fitting surface of the packaging piece fits the horizontal plane is judged by inserting the plug gauge into the gap between the packaging piece and the horizontal plane.

[0008] Optionally, the size of the plug gauge is adjusted according to the required measurement accuracy of the warping stress.

[0009] Optionally, the measuring piece is a light measuring device, and whether the packaging piece fits the horizontal plane is judged by irradiating test light from one side of the packaging piece into the gap, receiving the test light on the other side by using the light measuring device, and judging the size of the light flux of the test light received by the light measuring device.

[0010] Optionally, the packaging piece comprises a first layer and a second layer, the second layer is connected to the first layer, the fitting surface is arranged on the first layer, and the warped surface is arranged on the second layer; or the fitting surface is arranged on the second layer, and the warped surface is arranged on the first layer.

[0011] Optionally, the first layer and the second layer are materials with different thermal expansion coefficients.

[0012] Optionally, the first layer is an encapsulating material, and the second layer is a substrate.

[0013] Optionally, the counterweight is a weight.

[0014] Compared with the prior art, the present application has at least the following beneficial effects: by using the relationship between action force and reaction force, the warping stress of the packaging piece is indirectly obtained by measuring the pressure applied on the packaging piece. This measurement method is simple, and the specific value of the warping stress can be accurately obtained without using special equipment. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The flowchart of the stress measurement method in an embodiment of the present application.

[0016] Figure 2This is a schematic diagram of the package and the horizontal plane in one embodiment of this application.

[0017] Figure 3 This is another schematic diagram of the package and the horizontal plane in one embodiment of this application.

[0018] Figure 4 In order to be in Figure 3 A schematic diagram showing the addition of counterweights to the surface of the intermediate package component.

[0019] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application.

[0020] Explanation of main component symbols

[0021] Package 100

[0022] First floor 110

[0023] Second floor 120

[0024] 130 bonding surface

[0025] Warped surface 140

[0026] 200 counterweights

[0027] Horizontal plane 300 Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] Please see Figure 1 and Figure 2 The embodiments disclosed in this application provide a stress measurement method for measuring the stress of a package 100. In this embodiment, the stress mainly refers to the warpage stress of the package 100. Please refer to the following: Figure 2 The encapsulation 100 includes a first layer 110 and a second layer 120 connected to the first layer 110, wherein the first layer 110 and the second layer 120 are made of materials with different coefficients of thermal expansion.

[0030] Specifically, the first layer 110 can be an encapsulation material, such as epoxy molding compound (EMC), used to encapsulate the chip. The second layer 120 can be a substrate, used to place the chip to be encapsulated.

[0031] It is understood that the first layer 110 and the second layer 120 can also be two other materials having different thermal expansion coefficients. For example, in some embodiments, the first layer 110 is an encapsulation material, and the second layer 120 is a lead frame. In other embodiments, the first layer 110 is a chip, and the second layer 120 is a substrate or a lead frame. In other embodiments, the first layer 110 and the second layer 120 can also be two substrates made of materials having different thermal expansion coefficients.

[0032] Referring again to Figure 1 , the stress measurement method includes the following steps:

[0033] At step S11, the package 100 is placed on a horizontal surface 300, and a gap is formed between the adhering surface 130 and the horizontal surface 300.

[0034] It is understood that, due to the different thermal expansion coefficients of the first layer 110 and the second layer 120, the package 100 will warp. The warping directions of the first layer 110 and the second layer 120 can be different due to the difference in thermal expansion coefficients, and thus affect the placement direction of the package 100 on the horizontal surface 300.

[0035] Referring again to Figure 2 , specifically, when the two ends of the package 100 warp toward the second layer 120, the side of the package 100 close to the second layer 120 is placed on the horizontal surface 300. The surface of the package 100 close to the horizontal surface 300 forms the adhering surface 130. The surface of the package 100 away from the horizontal surface 300 forms the warping surface 140. The two ends of the adhering surface 130 are in contact with the horizontal surface 300, and the part between the two ends is spaced apart from the horizontal surface 300. In this case, the adhering surface 130 is formed on the second layer 120, and the warping surface 140 is formed on the first layer 110.

[0036] Referring again to Figure 3 , likewise, when the two ends of the package 100 warp toward the first layer 110, the side of the package 100 close to the first layer 110 is placed on the horizontal surface 300. The surface of the package 100 close to the horizontal surface 300 forms the adhering surface 130. The surface of the package 100 away from the horizontal surface 300 forms the warping surface 140. The two ends of the adhering surface 130 are in contact with the horizontal surface 300, and the part between the two ends is spaced apart from the horizontal surface 300. In this case, the adhering surface 130 is formed on the first layer 110, and the warping surface 140 is formed on the second layer 120.

[0037] Obviously, by placing the side of the package 100 away from the warping direction towards the horizontal surface 300, the protruding part of the package 100 can be placed upwards, facilitating the placement of the counterweight 200 (see Figure 4 ) onto the package 100.

[0038] Step S12, placing the counterweight 200 at the center of the warping surface 140 of the package 100, so that the fitting surface 130 of the package 100 moves towards the horizontal surface 300.

[0039] In the present embodiment, the counterweight 200 comprises a plurality of counterweight pieces with different weights. The counterweight 200 or the counterweight pieces are objects with standard weights, for example, can be weights.

[0040] It can be understood that in the step S12, a plurality of counterweight pieces can be placed in order from large to small according to the weights of the counterweight pieces contained in the counterweight 200, until the fitting surface 130 of the package 100 fits the horizontal surface 300.

[0041] For example, the counterweight piece with larger weight is placed at the center of the warping surface 140 of the package 100 first. If the package 100 directly and closely fits the horizontal surface 300, it indicates that the warping stress of the package 100 is obviously smaller than the counterweight piece with larger weight, and the counterweight piece with smaller weight needs to be replaced. Such a cycle is repeated until a plurality of counterweight pieces are placed at the center of the warping surface 140 of the package 100, and then a gap exists between the package 100 and the horizontal surface 300. At this time, the size of the gap is observed or measured to determine whether the fitting surface 130 of the package 100 fits the horizontal surface 300.

[0042] By setting counterweight pieces with different weight specifications and placing them in order from large to small on the package 100, the size of the warping stress can be measured more accurately.

[0043] Step S13, determining whether the fitting surface 130 of the package 100 fits the horizontal surface 300.

[0044] It can be understood that if the gap between the fitting surface 130 of the package 100 and the horizontal surface 300 is small enough (for example, less than or equal to a certain target value), it can be determined that the package 100 has been fitted to the horizontal surface 300. If the gap is still large (for example, greater than a certain target value), it is determined that the package 100 has not yet been fitted to the horizontal surface 300, and the weight of the counterweight 200 needs to be changed, for example, by adding a counterweight with a smaller weight and / or adjusting the existing counterweight, until the package 100 has been fitted to the horizontal surface 300. The weight of the counterweight 200 can be stopped from being changed and step S14 can be performed.

[0045] It can be understood that there are many ways to measure the size of the gap between the package 100 and the horizontal surface 300. For example, in some embodiments, a plug gauge can be used to measure the size of the gap. Specifically, in the present embodiment, step S13 further comprises:

[0046] After placing the counterweight 200 in the center of the warping surface 140 of the package 100 each time, a plug gauge is inserted into the gap between the package 100 and the horizontal surface 300. It is determined whether the package 100 is fitted to the horizontal surface 300 according to whether the plug gauge can be inserted into the gap. If it cannot be inserted, it is determined that the package 100 is fitted to the horizontal surface 300, and step S14 is performed. If it can be inserted, it is determined that the package 100 is not fitted to the horizontal surface 300, and step S12 is continued, i.e., the weight of the counterweight 200 is changed and placed in the center of the warping surface 140 of the package 100, so that the fitting surface 130 of the package 100 gradually fits the horizontal surface 300.

[0047] It can be understood that the plug gauge has many size specifications, and when the measurement accuracy of the stress requirement is high, a smaller size can be selected. When the measurement accuracy of the stress requirement is low, a larger size can be selected. By using plug gauges of different specifications, the size of the gap between the package 100 and the horizontal surface 300 can be more accurately measured, and the size of the warping stress can be more accurately measured.

[0048] In some other embodiments, the size of the gap between the package 100 and the horizontal surface 300 can also be measured using a light measurement method. Specifically, step S13 comprises:

[0049] After each time the counterweight 200 is placed in the center of the warping surface 140 of the packaging 100, a control test light is emitted from one side of the packaging 100 into the gap between the packaging 100 and the horizontal plane 300, and the test light is received by a light measuring device (not shown) on the other side. In this way, whether the packaging 100 is attached to the horizontal plane 300 can be determined according to the amount of light flux of the test light received by the light measuring device. If the light flux is less than or equal to a target value, it is determined that the packaging 100 is attached to the horizontal plane 300, and step S14 is executed. If the light flux is greater than the target value, it is determined that the packaging 100 is not attached to the horizontal plane 300, and step S12 is continued, i.e., the weight of the counterweight 200 is changed and placed in the center of the warping surface 140 of the packaging 100, so that the attachment surface 130 of the packaging 100 gradually attaches to the horizontal plane 300.

[0050] It can be understood that only a part of the test light can pass through the gap, and the other part is blocked by the packaging 100. The light measuring device can receive the light passing through the gap on the other side of the packaging 100 and obtain the light flux of the part of the light. The size of the gap can be indirectly obtained according to the light flux. When the light flux is large, it indicates that the gap is large, and the weight of the counterweight 200 needs to be changed. When the light flux is small, it indicates that the gap is small. When the light flux is less than a target value, it indicates that the packaging 100 is attached to the horizontal plane 300, and the weight of the counterweight 200 can be stopped from being changed.

[0051] In step S14, when it is determined that the attachment surface 130 of the packaging 100 is attached to the horizontal plane 300, the stress is obtained according to the weight of the counterweight 200.

[0052] According to the principle that forces act on each other, only when the pressure applied by the counterweight 200 on the packaging 100 is equivalent to the warping stress, the packaging 100 can be close to the horizontal plane 300. Therefore, the weight of the counterweight 200 is approximately equal to the size of the warping stress. If the counterweight 200 includes a plurality of counterweight members, the size of the warping stress can be obtained by adding up the weights of all the counterweight members.

[0053] The present application uses the relationship between the acting force and the reaction force, indirectly obtains the warping stress of the packaging 100 by measuring the pressure applied on the packaging 100. The measurement method is simple, and the specific value of the warping stress can be accurately obtained without using special equipment, so that the adjustment and improvement of the packaging process parameters can be realized according to the measurement results of the warping stress.

[0054] Those skilled in the art will realize that the embodiments described herein are merely illustrative and are not intended to limit the scope of the application. Changes and modifications can be made to the embodiments without departing from the spirit and scope of the application.

Claims

1. A stress measurement method for measuring the warpage stress of a package, the package including a bonding surface and a warpage surface, the warpage surface being disposed opposite to the bonding surface, characterized in that, The stress measurement method includes: The package is placed on a horizontal surface, with a gap formed between the mating surface and the horizontal surface; A counterweight is placed at the center of the warped surface of the package to move the mating surface toward the horizontal plane, wherein the counterweight comprises multiple counterweights of different weights; Determine whether the bonding surface of the package is in contact with the horizontal plane; and When it is determined that the bonding surface of the package is in contact with the horizontal plane, the warping stress is obtained based on the weight of the counterweight.

2. The method as described in claim 1, characterized in that, The step of placing a counterweight at the center of the warped surface of the package to move the mating surface toward the horizontal plane includes: The counterweights are placed in descending order of weight so that the contact surface of the package is in contact with the horizontal plane.

3. The method as described in claim 1, characterized in that, The step of determining whether the bonding surface of the package is in contact with the horizontal surface includes: The size of the gap between the mating surface of the package and the horizontal plane is measured using a measuring instrument; Determine whether the gap is less than or equal to the target value; When it is determined that the gap is less than or equal to the target value, it is determined that the package is in contact with the horizontal plane; and When it is determined that the gap is greater than the target value, it is determined that the package is not in contact with the horizontal plane, and the step of placing a counterweight at the center of the warped surface of the package to make the contact surface move toward the horizontal plane continues.

4. The method as described in claim 3, characterized in that, The measuring component is a feeler gauge. The feeler gauge is inserted into the gap between the package and the horizontal surface, and the fit of the package is determined based on whether the feeler gauge can be inserted into the gap.

5. The method as described in claim 4, characterized in that, The size of the feeler gauge is adjusted according to the required measurement accuracy of the warping stress.

6. The method as described in claim 3, characterized in that, The measuring device is a light measuring device. By illuminating the gap from one side of the package with test light, the light measuring device receives the test light on the other side, and determines whether the package is in contact with the horizontal plane based on the magnitude of the luminous flux of the test light received by the light measuring device.

7. The method as described in claim 1, characterized in that, The encapsulation includes a first layer and a second layer, the second layer being connected to the first layer, the bonding surface being disposed on the first layer, and the warped surface being disposed on the second layer; or the bonding surface being disposed on the second layer, and the warped surface being disposed on the first layer.

8. The method as described in claim 7, characterized in that, The first layer and the second layer are made of materials with different coefficients of thermal expansion.

9. The method as described in claim 7, characterized in that, The first layer is an encapsulating material, and the second layer is a substrate.

10. The method as described in claim 1, characterized in that, The counterweight is a weight.

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