Surface nano-structured treatment process of optical module blank material

Abstract

The invention discloses a surface nano-structured treatment process for an optical module blank material, which belongs to the technical field of optical module manufacturing and comprises the following steps: substrate pretreatment: electrolytic polishing is performed on the surface of the optical module blank material, and the blank material adopts aluminum; preparing a multi-scale hole array: generating array holes in the surface of the optical module blank material by adopting laser interference; fractal reaming: applying gradient pulse voltage to the optical module; a gradient contraction neck with the diameter smaller than that of the array hole is formed at the hole opening of the array hole through the confinement corrosion effect of the reverse pulse, and a forked dendritic structure is generated on the inner wall of the array hole; and structure stabilization treatment: coating an Al2O3 layer through atomic layer deposition, and filling grain boundary defects at branch nodes of the forked dendritic structure. According to the process, the surface energy and the thermal stability of the optical module blank can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical module manufacturing, and in particular relates to a surface nanostructuring process for an optical module blank. Background Art

[0002] Optical modules, as core components of modern optical communication systems, are widely used in data centers, 5G networks, fiber-to-the-home (FTTH), and long-haul backbone transmission. Their core function is to achieve efficient conversion and transmission of optical and electrical signals. These modules involve multiple key components, including lasers (LDs), photodetectors (PDs), optical lenses, and waveguide structures. The surface properties of optical module blanks (typically metal or ceramic substrates), the carrier of these optical components, directly impact optical coupling efficiency, heat dissipation, and long-term reliability. In high-speed optical communications, the transmission rate of optical modules has increased from the early 10 Gbps to 800 Gbps and even 1.6 Tbps, placing higher demands on the material's surface precision and thermal management capabilities. Currently, aluminum (Al) and aluminum nitride (AlN) are the mainstream blank substrates due to their high thermal conductivity (Al: 237 W / mK, AlN: 320 W / mK) and low cost. However, their raw surface properties struggle to meet these requirements. Summary of the Invention

[0003] In view of this, an object of the present invention is to provide a surface nanostructuring treatment process for an optical module blank, which can improve the surface energy and thermal stability of the optical module blank.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The surface nanostructuring treatment process of the optical module blank disclosed in the present invention comprises the following steps:

[0006] Substrate pretreatment: electrolytic polishing of the surface of the optical module blank, wherein the blank is made of aluminum;

[0007] Multi-scale hole array preparation: Laser interferometry is used to generate array holes on the surface of the optical module blank;

[0008] Fractal hole expansion: A gradient pulse voltage is applied to the optical module. Through the confined erosion effect of the reverse pulse, a gradient contraction neck with a smaller hole diameter than the array hole is formed at the hole mouth, generating a bifurcated dendritic structure on the inner wall of the array hole.

[0009] Structural stabilization treatment: Atomic layer deposition is used to coat the Al2O3 layer to fill the grain boundary defects at the branch nodes of the bifurcated dendritic structure.

[0010] Furthermore, the aperture D of the array holes ranges from 80 to 120 nm, the pitch between two adjacent array holes is from 1.5D to 3D, and the hole depth is from 3D to 10D.

[0011] Furthermore, under atomic force microscopy, the curvature radius of the gradient contraction neck is controlled by adjusting the ratio of the reverse voltage to the electrolyte viscosity, and the relationship is as follows:

[0012]

[0013] in is the curvature radius of the gradient shrinkage neck, is the viscosity of the electrolyte, V is the reverse voltage, K is 0.25 mPa·V⁻¹·M⁻¹, and H+ is the hydrogen ion concentration in the electrolyte.

[0014] Furthermore, the aperture change is detected in real time by an optical interferometer, and the size of the aperture diameter is controlled in real time by controlling the time and temperature of the reverse pulse.

[0015] Furthermore, branch holes are formed on the surface of the optical module blank. After laser interference generates a main hole array on the surface, nano-scale pits are created at the edges of the holes, which serve as nucleation points for the branch holes. Pulse voltage-induced corrosion expands directionally from the main holes to the pits, forming a branch network through channel connection.

[0016] Furthermore, the inner wall surfaces of the branch holes and the channels are coated with an Al2O3 layer.

[0017] The beneficial effects of the present invention are:

[0018] The laser interference-generated array of holes in this invention, combined with electrochemical fractal hole expansion, forms a multi-level interconnected network, significantly increasing the surface area and significantly improving the heat dissipation efficiency of the optical module. After the gradient constriction neck and fractal branching structure are coated with Al2O3 via ALD, the rate of pore size change during high-temperature thermal cycling is minimized. This is due to the passivation effect of Al2O3 on grain boundary defects, which increases grain boundary migration energy. The process of this invention can improve the surface energy and thermal stability of the optical module.

[0019] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention provides the following drawings for illustration:

[0021] Figure 1 is a flow chart of the treatment process of the present invention;

[0022] Figure 2Schematic diagram of the structure of the main hole and branch holes of the present invention;

[0023] Figure 3 Schematic diagram of the bifurcated dendritic structure. DETAILED DESCRIPTION

[0024] like Figures 1 to 3 As shown, the surface nanostructuring treatment process of the optical module blank disclosed in the present invention includes the following steps:

[0025] Substrate pretreatment: The surface of the optical module blank, made of aluminum, is electropolished using a phosphoric acid-ethanol solution at a voltage of 20V for 3 minutes to achieve a mirror-like surface roughness Ra < 5nm. This electropolishing method achieves a surface roughness Ra < 5nm for the aluminum substrate, providing an atomically flat substrate for subsequent nanostructure growth and preventing uneven energy distribution caused by light scattering during laser interference. This pretreatment reduces fluctuations in the laser ablation threshold and improves the consistency of the main hole diameter.

[0026] Multi-scale hole array preparation: femtosecond laser dual-beam spatial interference was used, with a laser wavelength of 1030 nm, a pulse width of 500 fs, and an energy density of 1.5 J / cm 2 , laser interference is used to generate array holes on the surface of the optical module blank;

[0027] Fractal hole expansion: In a 0.3M oxalic acid electrolyte, a gradient pulse voltage is applied to the optical module. The pulse voltage adopts a forward direction of 40V and a reverse direction of 10V, a duty cycle of 1:4, and a frequency of 10Hz. Through the confined corrosion effect of the reverse pulse, a gradient contraction neck with a hole diameter smaller than the array hole diameter is formed at the hole mouth of the array hole, and a bifurcated dendritic structure is generated on the inner wall of the array hole.

[0028] The formation principle of the gradient shrinkage neck is as follows: in the reverse voltage stage, the curvature enhancement effect at the pore mouth leads to the concentration of current density, which preferentially corrodes the edge of the pore mouth. The oxalic acid electrolyte forms a local acidic zone at the pore mouth, which can also accelerate the dissolution of the metal. Due to the electric field concentration effect, the metal ions in the high curvature area (such as the edge corners) are preferentially dissolved, resulting in the inhibition of lateral corrosion (radial expansion). The corrosion product Al(OH)3 accumulates rapidly at the pore mouth to form a passivation layer, which limits lateral etching. The low curvature area is mainly longitudinally corroded (along the depth direction of the pore). Inside the pore, the diffusion is limited, resulting in Al 3+ When the concentration is saturated, the corrosion rate decreases, forming a self-inhibition effect.

[0029] Table 1 shows the influence of various parameters on the curvature radius and pore size. The curvature radius gradient generated by the gradient contraction neck can form a stepped capillary pressure.

[0030] Table 1

[0031] Control parameters Effect of curvature radius Aperture influence Optimize Window Reverse voltage Each +1V→rc↓15nm Each +1V→d↓8nm -5V~-15V Pulse frequency Gradient disappears when >20Hz Every +1Hz→d↑3nm 5-15Hz Electrolyte pH When pH < 1.5, rc fluctuation increases pH -0.5 → d↓10nm 1.2-2.0 temperature Every +10℃→rc↑20nm Every +10℃→d↑12nm 20-40℃

[0032] The pressure gradient Where γ represents the surface tension of the liquid (water, γ = 72 mN / m), and r1 and r2 represent the radii at two different hole depths. The resulting stepped capillary pressure drives directional flow of the liquid / molten phase, acting on the solder during soldering, enabling self-aligned filling at high temperatures, meeting practical requirements. Furthermore, the gradient curvature acts as an elastic transition zone, reducing stress concentration caused by thermal expansion coefficient mismatch.

[0033] Structural stabilization treatment: A 2nm thick Al2O3 layer is deposited via atomic layer deposition (ALD) to fill the grain boundary defects at the branch nodes of the bifurcated dendritic structure. The Al2O3 layer coating allows for more uniform growth of the surface oxide layer.

[0034] Thermal atomic layer deposition was used, using trimethylaluminum and water as the precursor. A single cycle consisted of a TMA pulse (0.1s) → a purge (5s) → a H₂O pulse (0.1s) → a purge (5s). During the Al₂O₃ layer deposition process, the TMA to H₂O pulse time ratio was 1:1, and the purge gas flow rate was ≥200 sccm.

[0035] The laser interference-generated array holes and electrochemical fractal hole expansion in this invention form a multi-level interconnected network, significantly increasing the surface area and significantly improving the heat dissipation efficiency of the optical module. After the gradient constriction neck and fractal branching structure are coated with Al2O3 via ALD, the pore size change rate under 800°C high-temperature thermal cycling is reduced. This is due to the passivation effect of Al2O3 on grain boundary defects, which improves grain boundary migration energy. Using this process, the gradient capillary pressure generated by the fractal channel forms an internal stress field. Raman spectroscopy stress mapping verifies that this partially offsets thermal stress at high temperatures, thereby improving the surface energy and thermal stability of the optical module.

[0036] In this embodiment, the aperture D of the array holes ranges from 80 to 120 nm, and the pitch between two adjacent array holes is 1.5D to 3D, which can avoid signal crosstalk caused by optical coupling of adjacent holes. The hole depth is 3D to 10D, and a high aspect ratio structure is used to increase the capillary pressure, drive the coolant penetration rate to increase, and ensure the mechanical strength of the structure.

[0037] In this embodiment, under the observation of atomic force microscopy, the curvature radius of the gradient contraction neck is controlled by adjusting the ratio of the reverse voltage to the viscosity of the electrolyte, and the relationship is as follows:

[0038] ,

[0039] in is the curvature radius of the gradient shrinkage neck, is the viscosity of the electrolyte, V is the reverse voltage, K is 0.25 mPa·V⁻¹·M⁻¹, and H+ is the hydrogen ion concentration in the electrolyte. Viscosity is introduced into the formula The coupling term with H+ can compensate for the performance fluctuation caused by electrolyte aging.

[0040] In this embodiment, the aperture change is monitored in real time by an optical interferometer, and the size of the aperture diameter is controlled in real time by controlling the time and temperature of the reverse pulse. The aperture change is detected in real time and the reverse pulse time is adjusted by feedback so that the final aperture deviation is <±3nm, where the traditional process is ±20nm. For example, when an aperture deviation of +5nm is detected, the system automatically extends the reverse pulse time by 0.1s and compensates by additional Al(OH)3 deposition. Measured by an infrared thermal imager, local cooling can suppress the expansion of the heat-affected zone, making the temperature gradient in a 500nm deep hole <5℃ / μm, thereby avoiding the fracture of the branch structure due to thermal deformation.

[0041] In this embodiment, the optical module blank also has branch holes formed on its surface. Laser interference generates a main hole array on the surface, then creates nanoscale pits at the hole edges, which serve as nucleation points for the branch holes. Pulsed voltage-induced corrosion then directionally expands from the main hole toward the pits, connecting them through channels to form a branch network. Specifically, the main beam forms the main hole, and an additional vortex phase plate generates three equiangular satellite spots around each main focus, which then form the branch holes.

[0042] In this embodiment, the inner surfaces of both the branch holes and the channels are coated with an Al2O3 layer. Scratch testing shows that the Al2O3 layer improves the adhesion of the inner walls of the branch channels, preventing fluid erosion and structural peeling. The coating also reduces the corrosion rate of the channels in an acidic environment with a pH of 3 from 10 nm / min to 0.2 nm / min.

[0043] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. The surface nanostructuring process of the optical module blank is characterized by: The following steps are involved: Substrate pretreatment: electrolytic polishing of the surface of the optical module blank, wherein the blank is made of aluminum; Multi-scale hole array preparation: Laser interferometry is used to generate array holes on the surface of the optical module blank; Fractal hole expansion: A gradient pulse voltage is applied to the optical module. Through the confined erosion effect of the reverse pulse, a gradient contraction neck with a smaller hole diameter than the array hole is formed at the hole mouth, generating a bifurcated dendritic structure on the inner wall of the array hole. Structural stabilization treatment: Atomic layer deposition is used to coat the Al2O3 layer to fill the grain boundary defects at the branch nodes of the bifurcated dendritic structure.

2. The process for surface nanostructuring of an optical module blank according to claim 1, wherein: The aperture D of the array holes ranges from 80 to 120 nm, the distance between two adjacent array holes is from 1.5D to 3D, and the hole depth is from 3D to 10D.

3. The surface nanostructuring treatment process for an optical module blank according to claim 2, characterized in that: Under atomic force microscopy, the curvature radius of the gradient contraction neck is controlled by adjusting the ratio of reverse voltage to electrolyte viscosity, and the relationship is as follows: ,in is the curvature radius of the gradient shrinkage neck, is the electrolyte viscosity, Reverse voltage ，K Take 0.25 mPa·V⁻¹·M⁻¹, H + is the hydrogen ion concentration in the electrolyte.

4. The process for surface nanostructuring of an optical module blank according to claim 3, wherein: The aperture change is detected in real time by an optical interferometer, and the aperture diameter is controlled in real time by controlling the time and temperature of the reverse pulse.

5. The process for surface nanostructuring of an optical module blank according to any one of claims 1 to 4, characterized in that: Branch holes are also formed on the surface of the optical module blank. After laser interference generates a main hole array on the surface, nano-scale pits are created at the edges of the holes to serve as nucleation points for the branch holes. Pulse voltage-induced corrosion directionally expands from the main holes to the pits, forming a branch network through channel connection.

6. The process for surface nanostructuring of an optical module blank according to claim 5, characterized in that: The inner wall surfaces of the branch holes and channels are coated with Al2O3 layers.

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