A hemispherical lens coupling method for terahertz optoelectronic chip

Abstract

The present invention discloses a method for coupling a terahertz optoelectronic chip with a hemispherical lens. The method includes ultrasonic cleaning of a printed circuit board (PCB) and a hemispherical lens. The flat side of the hemispherical lens is then buckled onto the back of the PCB. Ultraviolet glue is dripped into the joint and cured with a UV lamp. The PCB and hemispherical lens are then fixed to a base. A two-dimensional imager is used to align the center hole of the terahertz optoelectronic chip with the center of the hemispherical lens. Finally, a chip placement machine is used to couple the terahertz optoelectronic chip and the hemispherical lens. This method can be used in the production process of transmitting or receiving chips. The coupling method has a high degree of standardization, good compatibility, and good repeatability, making it suitable for large-scale production.

Description

Technical Field

[0001] The present 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 have a wide range of applications in communications, military, astronomy and other fields.

[0003] In the communications field, terahertz space communications combine the advantages of both laser and microwave communications. Compared to laser communications, terahertz communications offer wider beams, easier receiver alignment, and lower quantum noise. Compared to microwave bands, terahertz antenna systems can be miniaturized and planarized. Due to the limited channel attenuation experienced in the atmosphere, terahertz communications are more suitable for satellite space communications. They can be used to build broadband, mobile, high-speed information networks between satellites, between satellites and the ground, and within local area networks.

[0004] In the military, terahertz waves can penetrate "black barriers." High-speed near-space vehicles and those re-entering the atmosphere (such as missiles and spacecraft) generate plasma with frequencies of tens of GHz around them, creating a "black barrier" communication blind spot, causing radio telemetry signals to rapidly decay and be interrupted. Terahertz wave communication is the only communication tool that can penetrate plasma.

[0005] In the field of astronomical exploration, terahertz radiation accounts for over 50% of the Milky Way's galaxy's radiation power. Therefore, terahertz space exploration is crucial for inferring stellar evolution and the composition and state of nebular gases. Devices that generate terahertz waves include photoconductive and photodiode types. For photoconductive devices, commonly used substrates include GaAs in the 800nm ​​band and InGaAs in the 1550nm band.

[0006] Due to the significant difference in refractive index between common optoelectronic chip substrates and air, most terahertz waves in the substrate are unable to escape into the air due to total internal 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 significantly improved, thereby enhancing 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 the 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 of which are as follows:

[0009] a) Create hollow sections in the center and edge of the printed circuit board to accommodate the terahertz optoelectronic chip and the edge of the observation hemispherical lens. Place the printed circuit board and hemispherical lens in acetone and isopropyl alcohol solutions, respectively. Clean them ultrasonically for 10 minutes, and then dry them with a nitrogen gun.

[0010] b) Place the printed circuit board face down, and buckle the flat side of the hemispherical lens on the back of the printed circuit board, aligning it with the positioning silk-screen ring. Add an appropriate amount of UV glue to 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.

[0011] c) Place the printed circuit board with the front side facing upwards and the hemispherical lens with the spherical surface facing downwards in the custom base and fix it under the imager;

[0012] d) Use a two-dimensional imager to find the edge of the hemispherical lens located in the hollowed-out portion of the printed circuit board. Use the three-point method to determine the center of the hemispherical lens. Align the center hole of the terahertz optoelectronic chip with the center of the circle, placing it so that the center of the chip pattern aligns with the center of the hemispherical lens.

[0013] e) Align the chip head with the terahertz optoelectronic chip under the chip placement machine, apply constant pressure to the terahertz optoelectronic chip for a period of time, and simultaneously drip an appropriate amount of UV glue into the junction of the terahertz optoelectronic chip and the hemispherical lens during the pressure application process. Use a UV lamp to irradiate for 3 to 5 minutes to completely cure it. After the glue is cured, remove the pressure;

[0014] f) Finally, the sample was placed in a hot air oven and baked at 50°C for 12 hours to age the UV glue, 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.

[0015] The hemispherical lens coupling method for a terahertz optoelectronic chip, step a) further comprises opening a fixing hole on the outside of the printed circuit board for fixing to the base.

[0016] In the hemispherical lens coupling method for a terahertz optoelectronic chip, the pressure in step e) is a pressure corresponding to 8 to 10 atmospheres.

[0017] In the hemispherical lens coupling method for a terahertz optoelectronic chip, the hemispherical lens has a shape of a standard hemisphere, a super hemisphere, or a sub-hemisphere, and does not require an additional boss design.

[0018] In the hemispherical lens coupling method for a terahertz optoelectronic chip, the hemispherical lens material is high-resistance silicon, HDPE or TPX.

[0019] In the hemispherical lens coupling method for a terahertz optoelectronic chip, the substrate material of the terahertz optoelectronic chip is GaAs or InP / InGaAs.

[0020] The beneficial effect of the present invention is that the present invention forms a complete terahertz transmitting or receiving device by adhering a hemispherical lens to the back of a printed circuit board, and using the chip head of a chip placement machine to couple the chips placed on the lens with constant pressure, and then uses ultraviolet glue to bond them together, thereby greatly enhancing the efficiency of the chip in transmitting or absorbing terahertz waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the three-dimensional structure of the device used in the method of the present invention;

[0022] Figure 2 is a side view schematic diagram of the device during coupling;

[0023] Figure 3 It is a top view of the device after coupling is completed;

[0024] Figure 4 is a side view of the device after coupling is completed;

[0025] Figure 5 It is based on the change of terahertz electric field intensity over time tested by terahertz time-domain spectrometer;

[0026] Figure 6 It is the frequency spectrum obtained based on fast Fourier transform.

[0027] 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

[0028] The following is a further detailed, clear and complete description of how the present invention is implemented in conjunction with specific embodiments and drawings.

[0029] The present invention discloses a hemispherical lens coupling method for a terahertz optoelectronic chip. The device for implementing this coupling method includes a printed circuit board 6 with a hollow portion 3 and fixing holes 4, a custom base 2, a hemispherical lens 5, a terahertz optoelectronic chip 1, and a chip placement machine. The steps are as follows.

[0030] a) Hollow portions 3 were created in the center and at the edge of the printed circuit board 6 to accommodate the terahertz optoelectronic chip 1 and the edge of the observation hemispherical lens 5. The printed circuit board 6 and hemispherical lens 5 were placed in acetone and isopropyl alcohol solutions, respectively, and ultrasonically cleaned for 10 minutes. The surfaces were then dried using a nitrogen gun.

[0031] In this step, the hollow portion 3 is primarily used to observe the edge of the hemispherical lens 5. Using three points on the circular edge, the center of the circle can be found. This design facilitates alignment of the center of the terahertz optoelectronic chip 1 with the center of the hemispherical lens 5, eliminating the need for a custom positioning fixture. This step also includes fixing holes 4 on the outside of the printed circuit board 6 for securing it to the base 2.

[0032] The hemispherical lens 5 has a standard hemispherical, super-hemispherical, or sub-hemispherical shape and does not require an additional boss design. The hemispherical lens 5 is made of high-resistance silicon, HDPE, or TPX. The substrate material of the terahertz optoelectronic chip 1 is GaAs or InP / InGaAs.

[0033] b) Place the printed circuit board 6 with the front side facing downwards, and buckle the flat side of the hemispherical lens 5 onto the back side of the printed circuit board 6, aligning it with the positioning silk-screen ring. Drip an appropriate amount of UV glue into the connection between the hemispherical lens 5 and the printed circuit board 6, and use a UV lamp to irradiate it for 3 to 5 minutes to completely cure it; UV glue can cure quickly under ultraviolet light and has a low shrinkage rate.

[0034] The UV glue used in this step is generally a relatively viscous, transparent liquid that solidifies when exposed to UV light of sufficient intensity. The advantages of using UV glue as an adhesive are that it has good fluidity, low shrinkage, and strong adhesion to materials such as plastic and glass, making it suitable for bonding small-sized chips.

[0035] 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.

[0036] 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.

[0037] 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 using the three-point method, and align the center hole of the terahertz optoelectronic chip 1 with the center of the circle so that the center of the chip pattern is aligned with the center of the hemispherical lens 5.

[0038] e) Align the chip head with the terahertz optoelectronic chip 1 under the chip placement machine, apply constant pressure (usually a pressure corresponding to 8 to 10 atmospheres) to the terahertz optoelectronic chip 1 for a period of time. During the pressure application process, drip an appropriate amount of ultraviolet glue into the junction of the terahertz optoelectronic chip 1 and the hemispherical lens 5, and use an ultraviolet lamp to irradiate it for 3 to 5 minutes to completely cure it. After the glue is cured, remove the pressure.

[0039] The placement machine in this step applies a constant amount of pressure in the vertical direction and maintains it for a certain period of time. The advantage of using a placement machine for coupling is that it can apply a fixed amount of pressure. This benefit is twofold: first, it ensures process stability and repeatability; second, it can apply different amounts of pressure to chips of different sizes to achieve a close coupling effect.

[0040] f), finally, the sample is placed in a hot air oven and baked at 50°C for 12 hours to perform UV glue aging treatment, completing the coupling of the terahertz optoelectronic chip 1 and the hemispherical lens 5. The main structure after coupling 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.

[0041] The focusing effect of a hemispherical lens effectively concentrates terahertz waves, significantly improving their transmission power and responsivity. The coupling method of this invention first uses an imager for centering. Then, leveraging the constant pressure applied by a chip mounter, the optoelectronic chip is pressed onto the hemispherical lens, minimizing the interface gap. The devices produced using this process were characterized using the following equipment.

[0042] The light source used in the experiment was a mode-locked femtosecond laser developed by Daheng New Era, featuring a central wavelength of 800nm, a pulse width of less than 50fs, a repetition rate of 80MHz, and a maximum output power of 400mW. The laser was first split into pump and probe beams. The pump beam was converged onto the terahertz optoelectronic chip using a variable attenuation and focusing lens. The terahertz pulses emitted by the terahertz optoelectronic chip were focused onto a ZnTe crystal via two off-axis parabolic mirrors. The probe beam was similarly converged onto the ZnTe crystal via an optical delay stage. The ZnTe crystal modulated by the terahertz wave altered the polarization state of the pulsed laser, which was then detected by a balanced detector via a Wollaston prism. A phase-locked amplifier amplified and recorded the voltage signal output by the balanced detector, generating a sinusoidal voltage signal of the same frequency. This amplified signal was then applied to the electrodes of the terahertz optoelectronic chip. The phase-locked frequency was set to 8.337kHz, with an integration time of 30ms. All tests were conducted in atmospheric air.

[0043] 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 middle: 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 6The dotted line in the middle is the terahertz radiation intensity of the sample without a coupled hemispherical lens, and the solid line is the terahertz radiation intensity of the sample coupled with a hemispherical lens using this method. Its terahertz radiation intensity is increased by about 5 times under the same laser power and bias voltage.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some embodiments of its application. A person skilled in the art may make several modifications and improvements without departing from the inventive concept of the present invention, and all of these modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A hemispherical lens coupling method for a terahertz optoelectronic chip, characterized in that: Here are the steps: a) Opening hollow portions (3) in the center and edge of the printed circuit board (6), placing the printed circuit board (6) and the hemispherical lens (5) in acetone and isopropyl alcohol solutions, and then using ultrasonic cleaning to dry the surface with a nitrogen gun; b) Place the printed circuit board (6) with its front side facing downwards, buckle the flat side of the hemispherical lens (5) onto the back of the printed circuit board (6), drip UV glue into the joint between the hemispherical lens (5) and the printed circuit board (6), and irradiate with UV light to completely cure it; 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 base (2) and fix it, and then place it 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 head with the terahertz optoelectronic chip (1) under the chip placement machine, applying 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 it with an ultraviolet lamp to completely cure it; f), placing it in a hot air box for aging treatment to complete the coupling between the terahertz optoelectronic chip (1) and the hemispherical lens (5).

2. The hemispherical lens coupling method for a terahertz optoelectronic chip according to claim 1, characterized in that: The step a) further comprises providing 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 for a terahertz optoelectronic chip according to claim 2, characterized in that: The pressure in step e) is a pressure corresponding to 8 to 10 atmospheres.

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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