A filling process method for a large-area arrayed mercury cadmium telluride infrared detector

Abstract

The application discloses a lower filling process method for a super-large surface array mercury cadmium telluride infrared detector, which comprises the following steps: cleaning a mercury cadmium telluride infrared focal plane and a readout circuit; applying glue to the edge of the mercury cadmium telluride infrared focal plane connected with the readout circuit; placing the focal plane with the applied glue on an exhaust table to perform vacuum pumping, and keeping vacuum for a period of time after pumping to the limit vacuum; quickly releasing the vacuum of the exhaust table after waiting for the glue flow on the fourth edge to be uniform, and making the lower filling glue flow fill the gap between the device and the readout circuit by using the pressure difference; and finally, observing under a microscope, sucking away the excess filling glue on the mercury cadmium telluride infrared detector focal plane, and placing the mercury cadmium telluride infrared detector focal plane in a drying cabinet to wait for solidification to be completed. The lower filling time of the application is shortened to one fourth of the original time, the efficiency is greatly improved, and the application is not affected by effective flow time and edge effect and the like, and the probability of "void phenomenon" can be greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of infrared detectors, and particularly relates to a lower filling process method of a super-large array mercury cadmium telluride infrared detector. BACKGROUND

[0002] With the rapid development and gradual maturity of the third generation of infrared detectors, the demand for super-large array mercury cadmium telluride infrared detectors in the fields of space-based remote sensing, meteorology, and earth observation is increasing, and the research and manufacturing of super-large array mercury cadmium telluride infrared detectors have become a new research hotspot in the field of infrared technology.

[0003] Since the application field of super-large array mercury cadmium telluride infrared detectors requires high reliability, a lower filling process is performed after flip-chip interconnection to improve the reliability of the interconnection. The lower filling process often uses epoxy resin glue to fill the gap between the mercury cadmium telluride device and the readout circuit. The glue is coated on one side of the chip, and the glue fills the entire gap through capillary action. First, since the array is large, the flow requires a long time, and the effective flow time of the epoxy resin glue after configuration is limited. After this time, the viscosity of the glue increases, and the flow rate slows down. The filling glue cannot flow through the entire gap within this time, and the lower filling of the large array cannot be completed. Second, the glue flow is affected by the edge effect during the capillary flow process. The glue flow rate at the edge is fast, and the glue flow rate at the center is slow, which eventually leads to the inability to discharge air in the center area of the large array, and the glue cannot flow. This also causes the "void phenomenon". The "void phenomenon" in the lower filling process can seriously affect the performance of the device, and can cause "bulging" and large-area cracking during subsequent use. The "void phenomenon" can also seriously affect the reliability of the flip-chip interconnection. Currently, there are three lower filling methods: traditional lower filling, non-flowing lower filling, and pressure injection lower filling. The non-flowing lower filling method is prone to air bubbles around the indium column, and the pressure injection lower filling method generates air bubbles during the glue flow process due to the fast glue flow rate. The devices obtained by using these two methods have poor reliability. Therefore, there is currently no lower filling method that can solve the above problems without affecting the performance of the device. SUMMARY

[0004] In order to solve the above problems, a lower filling process method of a super-large array mercury cadmium telluride infrared detector is provided by combining the traditional lower filling and pressure injection lower filling methods. This method not only solves the "void phenomenon" in the lower filling process, but also does not affect the performance of the device. In addition, it can greatly improve the efficiency and quality of the lower filling of the super-large array mercury cadmium telluride infrared detector.

[0005] The specific steps of the lower filling process method of the super-large array mercury cadmium telluride infrared detector are as follows:

[0006] Step (1), prepare the underfill adhesive with epoxy resin as the main component, prepare an exhaust station and a microscope;

[0007] Step (2), clean the focal plane of the mercury cadmium telluride infrared detector, and clean the periphery of the readout circuit to ensure that there is no foreign matter around;

[0008] Step (3), glue, glue the edge of the device connected with the readout circuit, and glue the edge of the three edges, and glue only on both sides of the other edge, and do not glue the middle part;

[0009] Step (4), place the mercury cadmium telluride infrared detector focal plane completed in step (3) on the exhaust station to perform vacuum pumping, and maintain vacuum for a period of time after pumping to the limit vacuum, and then flow uniformly on the fourth edge, and then proceed to the next step;

[0010] Step (5), after completing step (4), quickly release the vacuum of the exhaust station, and utilize the pressure difference to make the underfill adhesive flow into the gap between the device and the readout circuit;

[0011] Step (6), after completing step (5), observe under the microscope, and suck the excess underfill adhesive on the mercury cadmium telluride infrared detector focal plane;

[0012] Step (7), place the mercury cadmium telluride infrared detector focal plane completed in step (6) into a drying cabinet for curing.

[0013] Further, the time of pumping to the limit vacuum in step (4) is less than the edge wrapping time, and the edge wrapping time is calculated as follows: first, repeat steps (1), (2) and (3) by using a test piece, stop timing after observing under the microscope after completing step (3), and stop timing after observing that the glue on the fourth edge flows full, to obtain the edge wrapping time. In addition, the edge wrapping time is also related to the glue width on both sides of the fourth edge, and the wider the width, the shorter the edge wrapping time. After pumping to the limit vacuum, a period of time is needed to make the underfill adhesive on the fourth edge flow uniformly, otherwise, after releasing the vacuum, voids will appear.

[0014] The beneficial effects of the present application include:

[0015] The underfill process is a common way to improve the reliability of interconnection. Since the area of the super large array mercury cadmium telluride infrared detector is large, the underfill flow is difficult, and the conventional method takes 4-5 hours to complete the underfill of one super large array mercury cadmium telluride infrared detector, and there are factors such as effective flow time of the filling glue and edge effect of the glue flow, so the probability of the occurrence of the cavity after the underfill is large. The underfill process of the super large array mercury cadmium telluride infrared detector is carried out by using the application, and the time required for completing the underfill process of one large array detector can be shortened to 40-50 minutes, which is one fourth of the original time, greatly improving the efficiency, and being not affected by the effective flow time and edge effect, etc., so that the probability of the occurrence of the "cavity phenomenon" can be greatly reduced. Therefore, the application can greatly improve the efficiency and quality of the underfill of the mercury cadmium telluride infrared detector focal plane. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a top view of the mercury cadmium telluride infrared detector focal plane, wherein 1 is a detector device, and 2 is a readout circuit.

[0017] Figure 2 It is a schematic diagram of the glue coating area, wherein 1 is a detector device, 2 is a readout circuit, and 3 is filling glue.

[0018] Figure 3 It is a schematic diagram of the flow of the glue after the vacuum is released.

[0019] Figure 4 It is a response signal diagram of the 4096x4096 array, center distance of 15μm mercury cadmium telluride infrared detector focal plane. (I) is an abnormal response signal diagram caused by the cavity, and the black circle area in the diagram is caused by the underfill cavity; (II) is a signal response diagram after the underfill process is completed by using the application. DETAILED DESCRIPTION

[0020] As shown in the drawings, a large array mercury cadmium telluride infrared detector with a 4096x4096 array and a center distance of 15μm is taken as an example for the underfill process, and the specific embodiments of the application are further described in detail: Figures 1-4 1. The underfill glue is prepared by mixing the curing agent and the epoxy resin, and the underfill glue can be obtained after uniform stirring;

[0021] 2. The mercury cadmium telluride infrared detector focal plane is cleaned, especially the edge of the device connected to the readout circuit, to ensure that the filling glue flows smoothly;

[0022]

[0023] ​3. Gluing, glueing the edge of the device and the readout circuit, glueing the edge of the three edges, glueing the fourth edge on both sides, the width of the glueing is one third of the length of the fourth edge, the middle third is not glued.

[0024] 4. Placing the HgCdTe infrared detector focal plane on the exhaust table to perform vacuum pumping, the vacuum value reaches 3x10 -5 Torr after 15 minutes, and maintaining the vacuum for 20 minutes;

[0025] 5. Releasing the vacuum, and using the pressure difference to make the lower filling glue flow through the gap between the device and the readout circuit;

[0026] 6. Observing under a microscope, and sucking the excess glue around;

[0027] 7. Placing the HgCdTe infrared detector focal plane in a drying cabinet to solidify.

[0028] When the width of the glueing on the fourth edge is different, the edge wrapping time is also different, when the width of the glueing on both sides of the fourth edge is one third of the length of the edge, through experiments, it can be determined that the edge wrapping time is 25 minutes, the time required in the fourth step is about 35 minutes, which is greater than the edge wrapping time, and is sufficient to ensure that the glue on the fourth edge flows uniformly, so the time for completing the lower filling process is about 45 minutes.

[0029] The appearance of the cavity in the application is also related to the limit vacuum during vacuum pumping, the smaller the limit vacuum value, the smaller the probability of the cavity appearing, for the 4096x4096 array, the center distance of the HgCdTe infrared detector is 15um, through experiments, it is found that the probability of the cavity appearing is extremely small when the vacuum value reaches 5x10 -5 Torr after 15 minutes, and it is also found that the larger the size of the HgCdTe infrared detector, the smaller the required vacuum value.

Claims

1. A process for filling under a large array of tellurium cadmium mercury infrared detector, characterized in that, The method comprises the following steps: Step (1), preparing an epoxy resin underfill adhesive, a vacuum table and a microscope; Step (2), cleaning the focal plane of a mercury cadmium telluride infrared detector and a readout circuit; Step (3), applying adhesive to the edge of the focal plane of the mercury cadmium telluride infrared detector connected to the readout circuit, wherein the three edges connected are fully coated with adhesive, and the other edge is only coated with adhesive on both sides without the middle part; Step (4), placing the mercury cadmium telluride infrared detector focal plane completed in step (3) on the vacuum table to perform vacuum pumping, and maintaining vacuum for a period of time after pumping to the limit vacuum, so that the adhesive on the other edge flows uniformly before the next step; Step (5), after completing step (4), quickly release the vacuum of the vacuum table, and use the pressure difference to make the underfill adhesive flow into the gap between the device and the readout circuit; Step (6), after completing step (5), observe under the microscope and suck off the excess underfill adhesive on the mercury cadmium telluride infrared detector focal plane; Step (7), placing the mercury cadmium telluride infrared detector focal plane completed in step (6) into a drying cabinet for curing.

2. The process of claim 1, wherein, The time for pumping to the limit vacuum in step (4) is less than the edge coating time, and the edge coating time is calculated as follows: First, repeat steps (1), (2) and (3) using test pieces, and start timing after completing step (3), and observe under the microscope, and stop timing when the adhesive on the fourth edge flows full, to obtain the edge coating time.

3. The process method according to claim 2, characterized in that: The time for maintaining vacuum after pumping to the limit vacuum in step (4) is used to make the underfill adhesive on the fourth edge flow uniformly to prevent voids after releasing the vacuum.

4. The process method according to any one of claims 1-3, characterized in that: The super-large array mercury cadmium telluride infrared detector array is 4096x4096 with a center distance of 15μm.

5. The process method according to claim 4, characterized in that: The value of the ultimate vacuum is 3 x 10 -5 Torr.

6. The process method according to claim 5, characterized in that: The time for maintaining vacuum after pumping to the limit vacuum is 20min.

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