RU2568341C1 - Method of forming channel for transmitting optical signal between components of electronic module - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method includes using a material, which is selected based on the wavelength of the optical radiation used, to make an optical component which is an optical radiation waveguide made in the form of two mirror symmetric diffraction gratings and a straight portion in between; using a crystal, which is a VCSEL radiation source, and a crystal which is a PD radiation detector, and attaching said crystals to a substrate; depositing an insulating layer or insulating layers up to the top plane of the crystals; using a known method to form current-conducting interconnections from the contact pads of the crystals; opening insulating layers over the emitting and receiving areas of the corresponding crystals and mounting the optical component with calculated accuracy on the corresponding place; fixing the component with a polymer layer around the periphery or with a thin photoresist layer, which is deposited on contact surfaces before mounting the optical component, and depositing insulating layers.

EFFECT: easier formation of a channel for transmitting an optical signal between components of an electronic module, improved performance of said channel.

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Description

The invention relates to electronics. It proposes a new channelization method for transmitting an optical signal between components of an electronic module.

What caused the transition to optics? The fact is that at high frequencies (transfer speeds) of several gigabits per second, strong distortion of the signals occurs in the copper conductors (tracks) of the printed circuit board, both due to an increase in the resistance of the conductors themselves and due to resonance phenomena.

The solution is sought in the use of an optical connection, when the initial electrical signal is converted into an optical signal using a microlaser, then the optical signal is transmitted through a fiber (polymer optical waveguide), the optical signal is received by a microphotodetector, and the optical signal is converted into the original electric signal.

In this case, the optical signal must be transmitted with the least loss, since the microlaser power is very small, and the radiation tends to be scattered to a large extent.

“Connections to light sources and detectors associated with electronic chips provide a variety of configuration options for optical interconnects that are sealed with flexible, durable films. <...>:

- waveguides attached to the surface of the board to connect the edge of the board with the chip or between the chips. <...>;

- a flexible jumper is used to connect to the upper surface of the chip. This configuration provides a variety of connections, such as end contact to the chip, chip to chip, or chip to clamp multiple optical fibers outside the board;

- a jumper outside the base from the end contact to the chip and between the chips;

- hybrid variants containing bonds either on or off the base to a mirror and a set of lenses to provide connections to the underside of the base or to the optical layer between the bases;

“A multi-tiered film waveguide provides a set of interconnects between the backplane, daughter and daughter boards” (http://www.circuitry.ru/jornal/article/2254).

To transmit an optical signal between the components of the electronic module, lasers and receivers made in the form of corresponding crystals are used. Features of the technology for producing these elements determine their design features: the emitting and receiving areas of the elements can be directed either up (the crystal is mounted on a substrate "face up") or down (the crystal is mounted on a substrate "face down"). Therefore, in order to transmit an optical signal, there is a problem of beam rotation.

In (http://chromisfiber.com/pdf/YSSon_OSAribbonPOF_OEFeb2011.pdf) to solve these problems it is proposed to use a flexible fiber optic tape, as well as focusing lenses and prisms 45 °. This reduces the "number of individual components to facilitate passive matching for mass production."

It should be noted, however, that flexible fiber optic connectors have poor performance.

In the dissertation (Karppinen M. High bit-rate optical interconnects on printed wiring board. Micro-optics and hybrid integration, Edita prima Oy, Helsinki, 2008, p. 71-72), microlenses and mirrors are used to turn the beam. However, lenses and mirrors require careful alignment, and in mass production this turns out to be a bottleneck.

In (Takahara, N. Optoelectronic Packaging Trends in Japan. Stanford University, US-Asia TMC, May 2003, p. 6), the beam sequentially from the laser passes through a transparent polymer, a microlens, air, again a microlens, a polymer, a mirror, an optical waveguide, again a mirror , polymer, microlens, air, again microlens, the polymer also enters the microphotodetector. It also requires careful installation of microlenses and mirrors.

Known diffraction of laser radiation by diffraction gratings (http: //mr.jinr.rii/fein/pdf/Optics_lab5.pdf).

Known diffraction gratings that operate only on reflection with a reflection angle of 90 °. A theoretical justification for this effect is contained in the papers presented in (http://ipes.creol.ucf.edu/Publications.aspx) and is illustrated in (S. Lardenois et al., Opt. Lett. 28, 1150 (2003)) .

This effect can be used to form a channel for transmitting an optical signal between the components of the electronic module. For this (see Fig. 1-5):

1. An optical component is made (Fig. 1), which is a waveguide of optical radiation made in the form of two mirror-symmetric diffraction gratings and a rectilinear section between them. A part is made with dimensions that take into account its location and the required tolerances for the linear dimensions and radii of curvature of the gratings (protrusions) of the grating, as well as the specified roughness parameters (see GOST 2789-73) of all surfaces of the part. The grating period is calculated based on the wavelength of the used optical radiation. The radii of curvature for each grating line are calculated from the focusing conditions of optical radiation in order to reduce the divergence of radiation from the radiation source and to maximize the illumination of the sensitive area of the radiation receiver. The material of the optical part is also selected based on the wavelength of the optical radiation. So, use Si (for a wavelength of 1.55 μm); photopolymer EpoCore 10, Micro Resist Technology (for a wavelength of 0.85 microns); photopolymer EpoCore 20, Micro Resist Technology (for a wavelength of 0.85 microns); Photopolymer SU-85 MicroChem Corporation (for a wavelength of 0.85 microns).

2. Take crystals 1 and 2 (VCSEL radiation source and radiation detector PD, respectively) and adhere to the substrate 3, which is made, for example, of silicon, silicon oxide or silicon nitride (Fig. 2).

3. Apply an insulating layer or insulating layers 4 to the upper plane of the crystals (Fig. 3).

4. In a known manner, conductive interconnects 5 are formed from the contact pads of the crystals, the insulating layers are opened above the emitting and receiving pads of the crystals 6, and the optical part 7 is installed with the calculated accuracy (Fig. 4).

5. The optical part 7 is fixed with a polymer layer around the perimeter or with a thin layer of photoresist deposited on contact surfaces before installation. Insulating layers 8 are applied (FIG. 5).

The advantage of using the invention for serial and mass production of electronic modules containing optical interconnects: there is no need for laborious adjustment of micromirrors and microlenses; the role of micromirrors and microlenses is played by diffraction gratings made in advance in the form of a single optical path - a single optical part.

The technical result of the invention: a significant simplification in the formation of the channel for transmitting the optical signal between the components of the electronic module with multiple repeatability and a significant improvement in the operational characteristics of this channel.

Claims (1)

The method of forming a channel for transmitting an optical signal between the components of the electronic module, which consists in the fact that from a material that is selected based on the wavelength of the used optical radiation, an optical part is made, which is an optical radiation waveguide made in the form of two mirror-symmetric diffraction gratings and a straight portion between them, this part being made taking into account its placement, wavelength and focusing conditions of the used optical radiation I with the desired tolerances in the linear dimensions of the radii of curvature of grooves (protrusions) of the lattice, and the specified parameters of roughness of the workpiece surface; take the crystal, which is the source of the VCSEL radiation, and the crystal, which is the receiver of the PD radiation, and glue them onto the substrate, apply the insulating layer or insulating layers to the upper plane of the crystals, form conductive interconnects from the contact pads of the crystals in a known manner, open the insulating layers above the emitting and receiving pads crystals and set the optical part with calculated accuracy in the appropriate place, fix it with a polymer layer around the perimeter or a thin layer we use photoresist, which is applied to the contact surfaces before installing the optical part, and the insulating layers are applied.

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