Hemispherical lens coupling method of terahertz photoelectric chip

Abstract

The invention discloses a hemispherical lens coupling method for a terahertz photoelectric chip, and the method comprises the steps: carrying out the ultrasonic cleaning of a printed circuit board and a hemispherical lens, buckling the plane side of the hemispherical lens on the back surface of the printed circuit board, dropping ultraviolet glue into the connection part, carrying out the solidification through an ultraviolet lamp, fixing the printed circuit board and the hemispherical lens on a pedestal, and carrying out the ultrasonic cleaning. The center hole of the terahertz photoelectric chip is aligned with the circle center of the hemispherical lens by using a two-dimensional imager, and finally the terahertz photoelectric chip and the hemispherical lens are coupled by using a chip mounter. The method can be used for the manufacturing process of the transmitting or receiving chip, and the coupling method is high in standardization degree, good in compatibility and good in repeatability and can be used for large-scale production and manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz optoelectronic chips, and in particular relates to a packaging manufacturing method for coupling a hemispherical lens with a chip. Background Art

[0002] The terahertz band generally refers to electromagnetic waves with a frequency range of 0.1 to 10 THz. Terahertz waves are widely used in communications, military, astronomy and other fields.

[0003] In the field of communications, terahertz space communications have the advantages of both laser communications and microwave communications. Compared with laser communications, terahertz communications have wider beams, are easier to align at the receiving end, and have lower quantum noise; compared with microwave bands, antenna systems can be miniaturized and planarized. Terahertz communications are more suitable for satellite space communications because of the certain channel attenuation in the atmosphere, and can be used to build broadband mobile high-speed information networks between satellites, between satellites and the ground, and local area networks.

[0004] In the military field, terahertz waves can penetrate the "black barrier". For high-speed near-space vehicles and vehicles re-entering the atmosphere (such as missiles, spacecraft, etc.), plasma with a frequency of tens of GHz will be generated around the aircraft, forming a "black barrier" communication blind spot, causing the radio telemetry signal to rapidly attenuate and interrupt. Terahertz wave communication is the only communication tool that can penetrate plasma.

[0005] In the field of astronomical detection, the radiation power in the terahertz band accounts for more than 50% of the Milky Way. Therefore, terahertz space detection is of great value in inferring the evolution of stars and the composition and state of nebula gases. The types of devices that generate terahertz waves include photoconductive type and photodiode type. For photoconductive type, commonly used substrates include GaAs in the 800nm ​​band and InGaAs in the 1550nm band.

[0006] Since the refractive index difference between the common optoelectronic chip substrate and the air is too large, most of the terahertz waves in the substrate cannot be emitted into the air due to total reflection. By coupling a hemispherical lens with a suitable refractive index to the optoelectronic chip, the efficiency of terahertz wave emission or reception can be greatly improved, thereby improving device performance. Summary of the invention

[0007] In order to increase the intensity of terahertz signals transmitted or received by a terahertz optoelectronic chip, the present invention proposes a method of coupling a hemispherical lens to a terahertz optoelectronic chip.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a hemispherical lens coupling method for a terahertz optoelectronic chip, the steps are as follows: a) Open hollow parts in the center and edge of the printed circuit board to place the terahertz optoelectronic chip and the edge of the hemispherical lens. Place the printed circuit board and the hemispherical lens in acetone and isopropanol solution in turn, clean them with ultrasound for 10 minutes, and then blow dry the surface with a nitrogen gun; b) Place the printed circuit board with the front side facing downwards, buckle the flat side of the hemispherical lens on the back of the printed circuit board, align it with the positioning silk-screen ring, drip a proper amount of UV glue at the connection between the hemispherical lens and the printed circuit board, and use a UV lamp to irradiate for 3 to 5 minutes to fully cure it; c) Place the printed circuit board with the front side facing upwards and the hemispherical lens with the spherical surface facing downwards in a customized base and fix it, and then place it under the imager; d) Use a two-dimensional imager to find the edge of the hemispherical lens located at the hollow part of the printed circuit board, determine the center position of the hemispherical lens by the three-point method, align the center hole of the terahertz optoelectronic chip with the center of the circle, and place it so that the center of the chip pattern is aligned with the center of the hemispherical lens; e) Align the chip head with the terahertz optoelectronic chip under the chip mounter, apply constant pressure to the terahertz optoelectronic chip for a period of time, and drip a proper amount of ultraviolet glue into the junction of the terahertz optoelectronic chip and the hemispherical lens during the pressure application process, and use ultraviolet light to irradiate for 3 to 5 minutes to fully cure it. After the glue is cured, remove the pressure; f), and finally, the sample was placed in a hot air oven and baked at 50°C for 12 hours to perform aging treatment on the UV glue, thereby completing the coupling of the terahertz optoelectronic chip and the hemispherical lens. The main structure after coupling includes a printed circuit board, a terahertz optoelectronic chip and a hemispherical lens.

[0009] The hemispherical lens coupling method for a terahertz optoelectronic chip, step a) also includes opening a fixing hole on the outside of the printed circuit board for fixing to the base.

[0010] In the hemispherical lens coupling method for a terahertz optoelectronic chip, the pressure in step e) is a pressure corresponding to 8 to 10 atmospheric pressures.

[0011] In the hemispherical lens coupling method of a terahertz optoelectronic chip, the shape of the hemispherical lens is a standard hemisphere, a super hemisphere or a sub-hemisphere, and no additional boss design is required.

[0012] In the hemispherical lens coupling method of a terahertz optoelectronic chip, the hemispherical lens material is high-resistance silicon, HDPE or TPX.

[0013] In the hemispherical lens coupling method of a terahertz optoelectronic chip, the substrate material of the terahertz optoelectronic chip is GaAs or InP / InGaAs.

[0014] The beneficial effect of the present invention is that the present invention forms a complete terahertz transmitting or receiving device by pasting a hemispherical lens on the back of a printed circuit board, and using a chip placement head of a chip placement machine to couple the chips placed on the lens with constant pressure, and using ultraviolet glue to adhere them, thereby greatly enhancing the efficiency of the chip in emitting or absorbing terahertz waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the three-dimensional structure of the device used in the method of the present invention; Figure 2 is a schematic side view of the device during coupling; Figure 3 A top view of the device after coupling is completed; Figure 4 is a side view of the device after coupling is completed; Figure 5 It is based on the change of terahertz electric field intensity over time tested by terahertz time-domain spectrometer; Figure 6 It is the frequency spectrum obtained based on fast Fourier transform.

[0016] The reference numerals are: 1—terahertz optoelectronic chip, 2—base, 3—hollow portion, 4—fixing hole, 5—hemispherical lens, 6—printed circuit board. DETAILED DESCRIPTION

[0017] The following is a further detailed, clear and complete description of how the present invention is implemented in conjunction with specific embodiments and drawings.

[0018] The present invention discloses a hemispherical lens coupling method for a terahertz optoelectronic chip, and a device for implementing the coupling method includes a printed circuit board 6 with a hollow portion 3 and a fixing hole 4, a customized base 2, a hemispherical lens 5, a terahertz optoelectronic chip 1, and a chip mounter, etc. The steps are as follows.

[0019] a) A hollow portion 3 is opened at the center and edge of the printed circuit board 6 to place the terahertz optoelectronic chip 1 and the edge of the hemispherical lens 5. The printed circuit board 6 and the hemispherical lens 5 are placed in acetone and isopropanol solutions in turn, and ultrasonic cleaning is used for 10 minutes, and then the surface is blown dry with a nitrogen gun.

[0020] In this step, the hollow portion 3 is mainly used to observe the edge of the hemispherical lens 5, and the center of the circle can be found by using three points on the circular edge. The advantage of this design is that the center of the terahertz optoelectronic chip 1 can be easily aligned with the center of the hemispherical lens 5 without the need for a customized positioning fixture. In this step, a fixing hole 4 is also opened on the outside of the printed circuit board 6 for fixing with the base 2.

[0021] The shape of the hemispherical lens 5 is a standard hemispherical, super hemispherical or sub-hemispherical, and no additional boss design is required. The material of the hemispherical lens 5 is high-resistance silicon, HDPE or TPX. The substrate material of the terahertz optoelectronic chip 1 is GaAs or InP / InGaAs.

[0022] b) Place the printed circuit board 6 with the front side facing downwards, buckle the flat side of the hemispherical lens 5 on the back side of the printed circuit board 6, align it with the positioning silk-screen ring, drip a proper amount of UV glue at the connection between the hemispherical lens 5 and the printed circuit board 6, and use a UV lamp to irradiate for 3 to 5 minutes to completely cure it; UV glue can cure quickly under ultraviolet light and has a low shrinkage rate.

[0023] The UV glue in this step is generally a relatively viscous transparent liquid, which will solidify when exposed to UV light of sufficient intensity. The advantage of using UV glue as an adhesive is that the glue has good fluidity, small shrinkage, strong adhesion to materials such as plastic and glass, and is suitable for bonding small-sized chips.

[0024] In this step, the hemispherical lens 5 is fixed to the back of the printed circuit board 6 by ultraviolet glue. The advantage of this design is that this method is compatible with most types of hemispherical lenses.

[0025] c) Place the printed circuit board 6 with the front side facing upward and the hemispherical lens 5 with the spherical surface facing downward in the customized base 2 and fix it, and then place it under the imager.

[0026] d) Use a two-dimensional imager to find the edge of the hemispherical lens 5 located at the hollow portion 3 of the printed circuit board 6, determine the center position of the hemispherical lens 5 by the three-point method, align the center hole of the terahertz optoelectronic chip 1 with the center of the circle, and place it so that the center of the chip pattern is aligned with the center of the hemispherical lens 5.

[0027] e) Align the chip head with the terahertz optoelectronic chip 1 under the chip mounter, apply a constant pressure (usually a pressure corresponding to 8 to 10 atmospheres) to the terahertz optoelectronic chip 1 for a period of time, and drip a proper amount of ultraviolet glue into the junction of the terahertz optoelectronic chip 1 and the hemispherical lens 5 during the pressure application process, and use an ultraviolet lamp to irradiate for 3 to 5 minutes to completely cure it, and remove the pressure after the glue is cured.

[0028] The placement machine in this step can apply a constant amount of pressure in the vertical direction downward and maintain it for a certain period of time. The advantage of using a placement machine for coupling is that a certain amount of pressure can be applied. The benefits are twofold. One is that the process stability and repeatability can be guaranteed. The other is that different amounts of pressure can be applied to chips of different sizes to achieve a close coupling effect.

[0029] f), finally, the sample is placed in a hot air oven and baked at 50°C for 12 hours to perform an aging treatment on the UV glue, thereby completing the coupling of the terahertz optoelectronic chip 1 and the hemispherical lens 5. The coupled main structure includes a printed circuit board 6, a terahertz optoelectronic chip 1 and a hemispherical lens 5, as shown in FIG. Figure 1 and Figure 2 As shown, the hemispherical lens 5 is fixed on the printed circuit board 6, and the terahertz optoelectronic chip 1 is fixed on the hemispherical lens 5. Figure 3 and Figure 4 shown.

[0030] The focusing effect of the hemispherical lens can effectively gather terahertz waves, so that the emission power or responsiveness of the terahertz waves is greatly improved. The coupling method of the present invention first uses an imager to perform center positioning, and then uses the characteristic of the chip mounter that can apply constant pressure to press the optoelectronic chip onto the hemispherical lens to minimize the interface gap. The device prepared by this process is obtained after performance characterization by the following equipment.

[0031] The light source used in the experiment is a mode-locked femtosecond laser developed by Daheng New Era Company, with a central wavelength of 800nm, a pulse width of less than 50fs, a repetition frequency of 80MHz, and a maximum output power of 400mW. The laser is first split into pump light and probe light. The pump light is converged onto the terahertz optoelectronic chip through variable optical attenuation and focusing lenses. The terahertz pulses radiated by the terahertz optoelectronic chip are focused onto the ZnTe crystal through two off-axis parabolic mirrors. The probe light is also converged onto the ZnTe crystal through an optical delay stage. The ZnTe crystal changes the polarization state of the pulsed laser under the modulation of the terahertz wave, and is detected by a balanced detector through a Wollaston prism. The phase-locked amplifier amplifies and records the voltage signal output by the balanced detector, and outputs a sinusoidal voltage signal of the same frequency, which is amplified and applied to both ends of the electrodes of the terahertz optoelectronic chip. The phase-locked frequency is set to 8.337kHz, the integration time is 30ms, and the tests are all carried out in an atmospheric environment.

[0032] The performance of the terahertz optoelectronic chip device coupled with a hemispherical lens prepared by the above method is reflected in Figure 5 and Figure 6 In: Figure 5 The dashed line is the terahertz radiation intensity of the sample without coupling the hemispherical lens, and the solid line is the terahertz radiation intensity of the sample coupled with the hemispherical lens using this method; Figure 6 The dotted line in the middle is the terahertz radiation intensity of the sample without coupling the hemispherical lens, and the solid line is the terahertz radiation intensity of the sample coupled with the hemispherical lens using this method. Its terahertz radiation intensity is increased by about 5 times under the same laser power and bias voltage.

[0033] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A hemispherical lens coupling method for a terahertz optoelectronic chip, characterized in that: Here are the steps: a), respectively opening hollow portions (3) at the center and edge of the printed circuit board (6), placing the printed circuit board (6) and the hemispherical lens (5) in acetone and isopropanol solutions in turn, using ultrasonic cleaning, and then blowing the surface dry with a nitrogen gun; b) With the front side of the printed circuit board (6) facing downward, the flat side of the hemispherical lens (5) is buckled onto the back side of the printed circuit board (6), ultraviolet glue is dripped into the connection between the hemispherical lens (5) and the printed circuit board (6), and ultraviolet light is used to irradiate it to completely cure it; c) placing the printed circuit board (6) with the front side facing upward and the hemispherical lens (5) with the spherical surface facing downward in the base (2) and fixing them, and then placing them under the imager; d) using a two-dimensional imager to find the edge of the hemispherical lens (5) located at the hollow portion (3), determining the center position of the hemispherical lens (5) by a three-point method, and aligning the center hole of the terahertz optoelectronic chip (1) with the center of the circle; e) aligning the chip mounting head with the terahertz optoelectronic chip (1) under the chip mounting machine, applying a constant pressure to the terahertz optoelectronic chip (1), and simultaneously dripping ultraviolet glue into the junction between the terahertz optoelectronic chip (1) and the hemispherical lens (5), and irradiating with an ultraviolet lamp to completely cure the glue; f), placing it in a hot air oven for aging treatment to complete the coupling between the terahertz optoelectronic chip (1) and the hemispherical lens (5).

2. A hemispherical lens coupling method for a terahertz optoelectronic chip according to claim 1, characterized in that: The step a) also includes opening a fixing hole (4) on the outside of the printed circuit board (6) for fixing to the base (2).

3. The hemispherical lens coupling method of a terahertz optoelectronic chip according to claim 2, characterized in that: The pressure in step e) is a pressure corresponding to 8 to 10 atmospheric pressures.

4. A hemispherical lens coupling method for a terahertz optoelectronic chip according to claim 1, 2 or 3, characterized in that: The hemispherical lens (5) is a standard hemispherical lens, a super hemispherical lens or a sub-hemisphere lens.

5. A hemispherical lens coupling method for a terahertz optoelectronic chip according to claim 1, 2 or 3, characterized in that: The material of the hemispherical lens (5) is high-resistance silicon, HDPE or TPX.

6. A hemispherical lens coupling method for a terahertz optoelectronic chip according to claim 1, 2 or 3, characterized in that: The substrate material of the terahertz optoelectronic chip (1) is GaAs or InP / InGaAs.

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