RU2561202C2 - Formation method of channel for transmission of optic signal between components of electronic module - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to communication equipment and can be used in optic systems. A prism is made from optically transparent material and it has a trapezoid at its bottom, the angles of which are equal to 45, 135, 135, 45°, and the lower side shall have the length of not more than 200 mm; with that, the prism is made with the required allowances for linear and angular dimensions, as well as allowable roughness; all the prism faces, except for the lower one, are coated by aluminium by means of a sputtering process; a crystal being a radiation source and a crystal being a radiation receiver is taken, and they are bonded to a substrate; an insulating layer or insulating layers are applied up to the upper plane of crystals; current-conducting interconnections are formed in a known manner from contact platforms of crystals and the insulating layers are opened above the radiating and receiving platforms of the corresponding crystals. In case it is required to reduce aperture of a light beam, microlenses formed after opening of insulating layers are installed in the cavity above the radiating and receiving platforms.

EFFECT: easier formation of an optic channel.

2 cl, 5 dwg

Description

The invention relates to electronics. It proposes a new method of forming a channel 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 sealed with flexible, durable films <...>:

- waveguides are 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/journal/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 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 solve the beam to solve these problems. However, lenses and mirrors require careful alignment and this is a bottleneck in mass production.

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

In (http://chromisfiber.com/pdf/YSSon_OSAribbonPOF_OEFeb2011.pdf) 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.

This method of forming a channel for transmitting an optical signal is taken as a prototype.

We propose to use one single prism and at the same time refuse to configure at all!

The technical result of the invention is 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.

This technical result is achieved as follows (Fig.1-5).

1. A prism 1 (FIG. 1) is made from an optically transparent material, which has a trapezium at the base, whose angles are 45, 135, 135 and 45 °, and the prism is made with the required tolerances for linear and angular dimensions, as well as permissible roughness. All faces of the prism, except the lower one, are coated with aluminum using the spraying process.

2. Take the crystal 2, which is the source of radiation of VCSEL, and the crystal 3, which is the receiver of radiation PD, and stick them on the substrate 4 (figure 2).

3. Apply an insulating layer (s) 5 to the upper plane of the crystals (FIG. 3).

4. In a known manner, conductive interconnects 6 are formed from the contact pads of the crystals, the insulating layers are opened above the emitting and receiving pads of the corresponding crystals (cavities 7 are formed) and prism 1 is installed with the calculated accuracy in the appropriate place (Fig. 4). In the case when it is required to reduce the divergence of the light beam, microlenses are installed in the cavity 7 above the emitting and receiving areas.

5. Fix the prism 1 with a polymer layer around the perimeter or with a thin layer of photoresist, which is applied to the contact surfaces before its installation. Apply the insulating layers 8 (figure 5). The passage of laser radiation from the emitting to the receiving area is shown.

The lower edge of the prism should have a length of not more than 200 mm, which covers practically possible cases (but there may be exceptions). This is because the condition must be satisfied - for any deviation of the lower face of the prism from the base after its installation, due to various factors, an allowable light flux must enter the radiation receiver.

For small angles of deviation of the prism (up to 0.5 °) from the ideal position, the displacement of the axial beam of the laser radiation (deviation from the center of the radiation receiver) will be: x = a * sin (α), where a is the distance between the centers of the emitting and receiving sites VCSEL and PD, respectively, α is the prism deflection angle.

If we assume that the permissible value of the flux arriving at the radiation receiver from the original (from the radiation source) is 25%, i.e. the axial beam offset is about 2/3 from the center, then for a receiving pad diameter of 45 microns (http://www.connector-optics.com/uploaded/Datasheets/25%20Gbit-s%20PD%20chips%20850%20nm % 20GB% 20final.pdf), we have that the permissible angle for the distance a = 200 mm will be equal to:

α = arcsin (x / a), α = arcsin (2/3 * 45/200000), α = 30 ".

If you accept the allowable offset 1/3 of the diameter of the receiving platform, then the allowable angle will be equal to α = 15 ".

Modern equipment allows you to get the value of the angle α after planarization equal to 0.4 "(http://www.dicko.co.jp/eg/solution/library/surfare.html) in terms of the vertical slope of 0.039 microns (see value Ry in the table).

The advantage of using the invention in the serial production of electronic modules containing optical interconnects is that there is no need for time-consuming mirror alignment; the role of mirrors is performed by the faces of a prism, which is made in advance.

A particularly significant effect of the invention is visible for the case of multicast optical signals when VCSEL and PD are installed in a row, and only one prism is used.

Claims (2)

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 a prism is made from an optically transparent material, characterized in that the prism at the base has a trapezoid whose angles are 45, 135, 135, 45 °, and the lower the side should have a length of not more than 200 mm, and the prism is made with the required tolerances for linear and angular dimensions, as well as acceptable roughness, all faces of the prism, except the bottom, are coated with aluminum using the spraying process; 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 areas of the respective crystals and establish a prism with the calculated accuracy in the appropriate place, fix it with a polymer layer around the perimeter or a thin layer of a photore ISTA, which is applied to the contacted surface prior to installation of the prism and applied insulating layers. 2. A method of forming a channel for transmitting an optical signal between components of an electronic module according to claim 1, characterized in that in the case when it is necessary to reduce the divergence of the light beam, microlenses are installed in the cavity above the emitting and receiving areas formed after opening the insulating layers.

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