Die bonding method to prevent die warpage

Abstract

To provide a die bonding method that prevents warping of a die 30.SOLUTION: A method includes contacting a die bonding device 50 with a glass carrier plate 32, heating a substrate 10 with a heating tray 20 at a temperature lower than the melting point of the solder balls 40 between a wiring layer 31 and the substrate 10, and heating the glass carrier plate with the die bonding device at a temperature lower than the melting point of the solder balls, making one of the substrate and the glass carrier plate with a first material and the other of the substrate and the glass carrier plate with a second material. The thermal expansion coefficient of the first material is smaller than that of the second material, and the temperature of the first material is higher than that of the second material. Thus, the length L1 of the substrate and the length L2 of the glass carrier plate are maintained equal during the heating. The method further includes heating the solder balls with a light source to a temperature above the melting point of the solder balls, and fixing the wiring layer to the substrate after the liquid solder is hardened. The length of the substrate and the length of the glass carrier plate are maintained equal during the cooling process to room temperature.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a die bonding method, and more particularly to a die bonding method for preventing warping of a die.

Background Art

[0002] The die bonding process is an extremely important part in the packaging of semiconductor post-processes. Die bonding by heating and pressurization is one of the die bonding means.

[0003] In a known die bonding method, a substrate is placed on a heating tray, a die is installed on the substrate, there are a plurality of solder balls between the wiring layer of the die and the substrate, a die bonding apparatus contacts the glass carrier plate of the die, the heating tray heats the substrate, and the substrate transfers its heat quantity to the plurality of solder balls Transmit and the heating temperature of the heating tray exceeds the melting point of the plurality of solder balls, the die bonding apparatus pressurizes and heats the glass carrier plate, and the glass carrier plate transfers its heat quantity to the plurality of solder balls through the wiring layer Transmit and the heating temperature of the die bonding apparatus exceeds the melting point of the plurality of solder balls, the plurality of solder balls melt into liquid solder and penetrate onto the substrate, and after the liquid solder hardens, the wiring layer is completely fixed to the substrate.

[0004] However, since the thermal expansion coefficients of the substrate and the glass carrier plate are different, and both the heating temperature of the heating tray and the heating temperature of the die bonding apparatus exceed the melting point of the plurality of solder balls, under the same temperature change conditions, the one with a larger thermal expansion coefficient has a longer length, and the one with a smaller thermal expansion coefficient has a shorter length between the substrate and the glass carrier plate. Moreover, as the temperature rises or falls, the difference in the change of the lengths of the substrate and the glass carrier plate becomes more significant, and finally the die warps.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The main object of the present invention is to provide a die bonding method for preventing die warpage, which achieves the purpose of preventing die warpage by controlling the temperatures of a substrate and a glass carrier plate according to the difference in coefficient of thermal expansion.

Means for Solving the Problems

[0006] In order to achieve the above object, the present invention provides a die bonding method for preventing die warpage, which includes the following steps.

[0007] A substrate is placed on a heating tray, a die is placed on the substrate, a plurality of solder balls are provided between a wiring layer of the die and the substrate, a die bonding apparatus contacts a glass carrier plate of the die, both the die bonding apparatus and the glass carrier plate can transmit light, and the length of the substrate and the length of the glass carrier plate are equal at room temperature.

[0008] The heating tray heats the substrate, and the substrate transfers its heat quantity to the plurality of solder balls Transmit and the heating temperature of the heating tray is lower than the melting point of the plurality of solder balls; the die bonding apparatus pressurizes and heats the glass carrier plate, and the glass carrier plate transfers heat quantity to the plurality of solder balls through the wiring layer Transmit and the heating temperature of the die bonding apparatus is lower than the melting point of the plurality of solder balls; and one of the substrate and the glass carrier plate is made of a first material, the other of the substrate and the glass carrier plate is made of a second material, the coefficient of thermal expansion of the first material is smaller than that of the second material, and the temperature of the first material is higher than that of the second material, so that the lengths of the substrate and the glass carrier plate are maintained equal during temperature rise.

[0009] Light projected from a light source passes through the die bonding apparatus and the glass carrier plate to heat the wiring layer, and the wiring layer transfers its heat quantity to the plurality of solder balls TransmitMoreover, since the heating temperature of the light source exceeds the melting point of the plurality of solder balls, the plurality of solder balls melt into liquid solder and penetrate onto the substrate.

[0010] By stopping the heating of the wiring layer by the projection of light from the light source, the After the liquid solder hardens, the wiring layer is completely fixed to the substrate, and By controlling the temperatures of the substrate and the glass carrier plate according to the difference in the coefficients of thermal expansion, the lengths of the substrate and the glass carrier plate are maintained equal during the process of cooling down to room temperature.

[0011] In some embodiments, the light source includes a quartz lamp, and the infrared rays projected from the quartz lamp pass through the die bonding device and the glass carrier plate to heat the wiring layer.

[0012] In some embodiments, the light source further includes a reflective cover, and the quartz lamp is installed inside the reflective cover to project infrared rays to the opening of the reflective cover.

[0013] In some embodiments, the light source further includes a convex lens, and the convex lens is disposed between the quartz lamp and the die bonding device. The quartz lamp projects infrared rays to the convex lens, and the convex lens converges the infrared rays.

[0014] In some embodiments, the light source further includes a laser module, and the laser beam projected from the laser module passes through the die bonding device and the glass carrier plate to heat the wiring layer.

[0015] In some embodiments, the heating temperature of the die bonding device is between 140°C and 270°C, and the heating temperature of the heating tray is between 140°C and 270°C.

[0016] In some embodiments, the size of the die bonding device is larger than the size of the die.

Advantages of the Invention

[0017] According to the present invention, in the process of preheating the solder ball, by controlling the temperatures of the first material and the second material according to the difference in the coefficient of thermal expansion, the substrate and the glass carrier plate can always maintain the same length under different temperature change conditions, regardless of whether the temperature is rising or falling, and warping of the die and residual internal stress can be avoided.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and reference numerals.

[0020] FIG. 1 is a flowchart of a die bonding method for preventing warping of a die according to the present invention. FIG. 2 is a schematic diagram of step S10 of the die bonding method for preventing warping of a die according to the present invention. FIG. 3 is a schematic diagram of step S20 of the die bonding method for preventing warping of a die according to the present invention. FIG. 4 is a schematic diagram of step S30 of the first embodiment of the die bonding method for preventing warping of a die according to the present invention. FIG. 5 is a schematic diagram of step S40 of the die bonding method for preventing warping of a die according to the present invention. FIG. 6 is a thermal expansion coefficient graph of the first material and the second material of the die bonding method for preventing warping of a die according to the present invention. The present invention provides a die bonding method for preventing warping of a die including the following steps.

[0021] In step S10, as shown in FIGS. 1, 2 and 6, the substrate 10 is placed on the heating tray 20, the die 30 is placed on the substrate 10, there are a plurality of solder balls 40 between the wiring layer 31 of the die 30 and the substrate 10, the die bonding device 50 contacts the glass carrier plate 32 of the die 30, both the die bonding device 50 and the glass carrier plate 32 can transmit light, and at room temperature, the length L1 of the substrate 10 is equal to the length L2 of the glass carrier plate 32.

[0022] In step S20, as shown in FIGS. 1 and 3, the heating tray 20 heats the substrate 10, and the substrate 10 transfers its heat to the plurality of solder balls 40 Transmit , and the heating temperature of the heating tray 20 is lower than the melting point of the plurality of solder balls 40; as shown in FIGS. 1 and 3, the die bonding device 50 pressurizes and heats the glass carrier plate 32, and the glass carrier plate 32 transfers heat to the plurality of solder balls 40 through the wiring layer 31 Transmit , and the heating temperature of the die bonding device 50 is lower than the melting point of the plurality of solder balls 40; and, as shown in FIGS. 1, 3 and 6, one of the substrate 10 and the glass carrier plate 32 is made of a first material, the other of the substrate 10 and the glass carrier plate 32 is made of a second material, the thermal expansion coefficient of the first material is smaller than the thermal expansion coefficient of the second material, and the temperature T1 of the first material is higher than the temperature of the second material T2, so that the length L1A of the substrate 10 and the length L2A of the glass carrier plate 32 are maintained equal during heating.

[0023] In step S30, as shown in FIGS. 1 and 4, the light projected from the light source 60 passes through the die bonding device 50 and the glass carrier plate 32 to heat the wiring layer 31, and the wiring layer 31 transfers its heat to the plurality of solder balls 40 Transmit Since the heating temperature of the light source 60 exceeds the melting point of the plurality of solder balls 40, the plurality of solder balls 40 melt into liquid solder and penetrate onto the substrate 10.

[0024] In step S40, as shown in FIGS. 1 and 5, By stopping the heating of the wiring layer 31 by the projection of light from the light source 60, After the liquid solder hardens, the wiring layer 31 is completely fixed to the substrate 10, and By controlling the temperatures of the substrate 10 and the glass carrier plate 32 according to the difference in the coefficients of thermal expansion, the length L1 of the substrate 10 and the length L2 of the glass carrier plate 32 are maintained equal during the process of cooling down to room temperature.

[0025] Thus, in the present invention, in the process of preheating the solder balls 40, by controlling the temperatures of the first material and the second material according to the difference in the coefficient of thermal expansion, the substrate 10 and the glass carrier plate 32 can have their lengths always maintained equal under different temperature change conditions, regardless of whether it is heating up or cooling down. Therefore, warping of the die 30 and residual internal stress can be avoided.

[0026] In the first embodiment, the heating temperature of the die bonding apparatus 50 is between 140°C and 270°C, and the heating temperature of the heating tray 20 is between 140°C and 270°C. More specifically, the melting point of the solder ball 40 varies depending on its content. Since the melting point of the solder ball 40 with the content used during die bonding usually exceeds 270°C, the heating temperatures of the die bonding apparatus 50 and the heating tray 20 need to be below 270°C, thereby avoiding the melting of the solder ball 40 into liquid solder. If the heating temperature is less than 140°C, the preheating temperature of the solder ball 40 becomes too low, and the heating time of the light source 60 for melting the solder ball 40 into liquid solder becomes longer, reducing the welding efficiency. Therefore, the method according to the present invention can sufficiently ensure the preheating temperature of the solder ball 40 by controlling the heating temperature between 140°C and 270°C, or can prevent the solder ball 40 from melting into liquid solder and improve the welding efficiency.

[0027] In the first embodiment, the size of the die bonding apparatus 50 is larger than the size of the die 30. Therefore, the die bonding apparatus 50 can pressurize and heat the die 30 at a uniform pressure and temperature, preventing warping of the die 30.

[0028] Preferably, in step S30, the light source 60 includes a quartz lamp 61, and further includes that the infrared rays projected from the quartz lamp 61 pass through the die bonding apparatus 50 and the glass carrier plate 32 to heat the wiring layer 31.

[0029] FIG. 7 is a schematic diagram of step S30 of the second embodiment of the die bonding method for preventing warping of the die according to the present invention. As shown in FIG. 7, the difference between the second embodiment and the first embodiment is that in step S30, the light source 60A further includes a reflection cover 62, and the quartz lamp 61 is installed in the reflection cover 62 to project infrared rays to the opening of the reflection cover 62.

[0030] FIG. 8 is a schematic diagram of step S30 of a third embodiment of a die bonding method for preventing warping of a die according to the present invention. As shown in FIG. 8, the difference between the third embodiment and the first embodiment is that in step S30, the light source 60B further includes a convex lens 63, the convex lens 63 is disposed between the quartz lamp 61 and the die bonding apparatus 50, and the quartz lamp 61 projects infrared rays onto the convex lens 63, and the convex lens 63 converges the infrared rays.

[0031] FIG. 9 is a schematic diagram of step S30 of a fourth embodiment of a die bonding method for preventing warping of a die according to the present invention. As shown in FIG. 9, the difference between the fourth embodiment and the first embodiment is that in step S30, the light source 60C is a laser module 64, and the laser beam projected from the laser module 64 passes through the die bonding apparatus 50 and the glass carrier plate 32 to heat the wiring layer 31.

[0032] The above are only preferred embodiments for explaining the present invention and are not intended to limit the present invention. Therefore, any modification or change made to the present invention without departing from the gist of the present invention also shall fall within the protection scope of the present invention.

Explanation of Reference Numerals

[0033] 10 Substrate 20 Heating Tray 30 Die 31 Wiring Layer 32 Glass Carrier Plate 40 Solder Ball 50 Die Bonding Apparatus 60, 60A, 60B, 60C Light Source 61 Quartz Lamp 62 Reflection Cover 63 Convex Lens 64 Laser Module L1, L1A, L2, L2A Length S10~S40 Steps T1, T2 Temperature

Claims

1. A die bonding method for preventing warping of a die, comprising: a substrate is placed on a heating tray, a die is placed on the substrate, a plurality of solder balls are provided between the wiring layer of the die and the substrate, a die bonding apparatus contacts the glass carrier plate of the die, both the die bonding apparatus and the glass carrier plate are capable of transmitting light, and the length of the substrate is equal to the length of the glass carrier plate at room temperature; the heating tray heats the substrate, the heat of the substrate is transmitted to the plurality of solder balls, and the heating temperature of the heating tray is lower than the melting point of the plurality of solder balls; the die bonding apparatus pressurizes and heats the glass carrier plate, the heat of the glass carrier plate is transmitted to the plurality of solder balls through the wiring layer, and the heating temperature of the die bonding apparatus is lower than the melting point of the plurality of solder balls; and one of the substrate and the glass carrier plate is made of a first material, the other of the substrate and the glass carrier plate is made of a second material, the coefficient of thermal expansion of the first material is smaller than the coefficient of thermal expansion of the second material, and the temperature of the first material is higher than the temperature of the second material, so that the lengths of the substrate and the glass carrier plate are maintained equal during heating; light projected from a light source passes through the die bonding apparatus and the glass carrier plate to heat the wiring layer, the heat of the wiring layer is transmitted to the plurality of solder balls, and the heating temperature of the light source exceeds the melting point of the plurality of solder balls, so that the plurality of solder balls melt into liquid solder and penetrate onto the substrate; after the liquid solder hardens, the wiring layer is completely fixed to the substrate, and the lengths of the substrate and the glass carrier plate are maintained equal during the process of cooling to room temperature; A die bonding method for preventing warping of a die, characterized by comprising the above.

2. The light source includes a quartz lamp, The die bonding method for preventing warping of a die according to claim 1, characterized in that infrared rays projected from the quartz lamp pass through the die bonding apparatus and the glass carrier plate to heat the wiring layer.

3. The light source further includes a reflective cover, The die warpage prevention die bonding method according to claim 2, wherein the quartz lamp is installed inside the reflection cover and projects infrared rays to the opening of the reflection cover.

4. The light source further includes a convex lens, The convex lens is disposed between the quartz lamp and the die bonding apparatus, The die warpage prevention die bonding method according to claim 2, wherein the quartz lamp projects infrared rays to the convex lens, and the convex lens converges the infrared rays.

5. The light source further includes a laser module, The die warpage prevention die bonding method according to claim 1, wherein the laser beam projected from the laser module passes through the die bonding apparatus and the glass carrier plate to heat the wiring layer.

6. The heating temperature of the die bonding apparatus is between 140°C and 270°C, The die warpage prevention die bonding method according to claim 1, wherein the heating temperature of the heating tray is between 140°C and 270°C.

7. The die warpage prevention die bonding method according to claim 1, wherein the size of the die bonding apparatus is larger than the size of the die.

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