The explosion of AI computing power drives the acceleration of optical module iteration. Which ceramic packaging products will benefit?

As data centers continue to increase their demand for data transmission bandwidth and transmission rate, traditional copper cable electrical connections can no longer meet the needs of high bandwidth and low latency. Therefore, optical communication technology has gradually become the main way to transmit data between cabinets within data centers and even between data centers due to its advantages such as high bandwidth, long-distance transmission capability, low power consumption and anti-interference. However, since the optical path must remain transparent, optical elements and devices are sensitive to moisture and have high requirements for heat dissipation, optical modules, which are key components to ensure data transmission in data centers, require extremely reliable packaging. Advanced ceramics, as a type of high-performance material with good chemical stability, high mechanical strength and good thermal conductivity, have shown unique advantages in the field of optical module packaging.

1. Ceramic packaging substrate, tube shell, base

Chip packaging can usually be divided into two types: airtight packaging and non-airtight packaging. Airtight packaging refers to completely sealing electronic components in an airtight shell filled with inert gas to prevent moisture, oxygen and other pollutants in the air from entering the package, avoiding oxidation, corrosion and other forms of degradation inside the device, and ensuring the long-term stability and reliability of the device. Therefore, optical communication devices and modules with high reliability requirements such as optoelectronic transmission and reception, optical switches, and control in optical fiber backbone networks, metropolitan area networks, broadband access, the Internet of Things, and data centers all require airtight packaging.

The main materials for airtight packaging are metals, ceramics, and glass. Ceramic materials have the characteristics of good insulation, high temperature resistance, wear resistance, corrosion resistance, light weight, and good thermal conductivity. In addition to providing excellent airtightness, they can also effectively conduct heat from the inside of the optical module to the external cooling system, thereby keeping the operating temperature of the internal components within a safe range and meeting the comprehensive performance of high-frequency and high-speed signal transmission. Therefore, ceramic products such as ceramic packaging substrates, tube shells, and bases are the preferred materials for airtight packaging of optical devices. At present, ceramic products for optical communications often need to be metallized and prepared into a multilayer co-fired ceramic (HTCC) insulating structure to provide devices with electrical signal transmission channels and optical coupling interfaces, provide mechanical support and airtight protection, solve the interconnection between chips and external circuits, and achieve high-speed conversion, coupling and transmission of electrical and optical signals.

2.Ceramic Heat Sink

When working, optical devices such as semiconductor lasers do not completely convert the injected current into output photoelectrons. A part of it will be lost as energy in the form of heat. With the development of AI technology and 5G communication, the power of a single optical module is getting larger and larger, and it is easier to accumulate a lot of heat. If this heat cannot be removed in time, it will have many adverse effects on the performance of components.

Generally speaking, there are two ways to dissipate heat for devices. One is to dissipate heat by natural convection of the surrounding air, but this method can only dissipate a small part of the heat. Therefore, most of the remaining heat needs to be dissipated by heat conduction, transferring the heat from the high temperature end to the low temperature end. The heat sink is an important carrier for heat transfer and is a key core component of heat dissipation technology. At present, heat sinks are usually made of ceramics, tungsten copper alloys, diamonds and other materials, and increase the heat dissipation area through their own structural design (such as fins, ribs, etc.) to achieve the purpose of rapid heat dissipation for the device. Among them, ceramic materials such as aluminum nitride, beryllium oxide, and silicon carbide have a relatively good match with the thermal expansion coefficients of semiconductor materials such as Si, InP, and GaAs, and have been widely used in semiconductor lasers.

3.Micro semiconductor refrigeration chip

As the power of optical modules increases, in order to ensure effective heat dissipation of optical devices, in addition to using heat sinks for passive heat dissipation, some high-power optical devices also need to use some active means to dissipate heat. MicroTEC (micro semiconductor cooling chip) is an effective solution for precise temperature control of optical chips.

A typical semiconductor refrigerator consists of a thermally conductive insulating layer formed by two ceramic substrates and p-type and n-type semiconductor materials (bismuth telluride) between the ceramic substrates. When direct current passes through these semiconductor elements, heat and cold energy transfer occurs at the junction, that is, one side absorbs heat and cools, while the other side releases heat and heats up, thereby achieving a cooling or heating effect. Usually, the ceramic substrates on both sides of the semiconductor refrigerator are mainly used to provide good heat conduction between the hot and cold ends, and to insulate the electrical components in the module from the heat sink on the hot side of the module and the object being cooled on the cold side. Currently, materials such as Al2O3 (aluminum oxide), BeO (beryllium oxide), and AlN (aluminum nitride) are commonly used.

4.Ceramic Ferrule and Sleeve

Fiber optic connectors are indispensable passive devices in fiber optic communication systems. They are mainly used for connecting fiber optic lines, connecting transmitter output ports/optical receiver input ports with optical fibers, connecting fiber optic lines with other optical devices, etc. In order to maximize the coupling of the light energy output by the transmitting optical fiber to the receiving optical fiber, it is necessary to use a precision-designed (the finished product accuracy must reach sub-micron level) ferrule and a ceramic sleeve to fix the optical fiber, so as to achieve the physical docking of the two end faces of the optical fiber, so that the optical signal can be continuous and form an optical path.

At present, the materials that can be used to prepare the ferrule include ceramics, metals or plastics. Among them, ceramic ferrules made of zirconium dioxide are widely used. The main material is zirconium dioxide (ZrO2), which has the characteristics of good thermal stability, high hardness, high melting point, wear resistance, and high processing precision.

As data centers and high-performance computing (HPC) systems are increasingly used in artificial intelligence (AI) smart devices, the role of optical modules becomes increasingly important. Due to their excellent chemical stability, mechanical strength, and thermal conductivity, ceramic products such as packaging substrates, packaging tubes, ceramic ferrules, and semiconductor coolers play a key role in different components of optical modules, and their demand will increase to a certain extent with the development of optical modules.