Active Solder Joining for Semiconductor Processing

S-Bond Technologies’ active solders are finding wide application in semiconductor processing equipment. Their capability to join a wide range of dissimilar materials and the fact that as a filler metal, their bonds are thermally conductive make S-Bond solders far superior to many other commercial bonding/thermal interface materials. Semiconductor processing applications include…

In sputter targets, the deposition/target materials is sputtered (high energy ion impacts displace a target’s atoms) onto an opposite surface to form a functional coating or other element layer in a computer chip, TV screen or other semiconductor device. The high energy impact of the deposited films require “sputter targets” to be cooled to keep the target material layer from melting. To cool the target, water is circulated in an aluminum or copper base plate.  S-Bond active solders can bond all metals and most ceramics that are commercially used to produce sputtered films. Active solders can bond these sputter targets to either Copper or Aluminum, bonding them at low temperatures (which minimizes thermal expansion mismatch stresses), without flux contamination/entrapment (which will contaminate the sputtering plasma), and with excellent thermal conductivity (a metallic bond with nearly no voids).

For probes and sensors, S-Bond active solders can bond silicon or carbide/carbon based devices (MEMS or other semiconductor based probes) directly to metal and metallic conductor leads. The low temperature active solders, when joining semi-conductor devices, impart low residual stresses and the joints are electrically and thermally conductive… good for signal transmittance and cooling.

Piezoceramics such as Pb-Zirconates (PZT) that impart force/small displacement or create ultrasonic pulses, can be bonded direct to metals with active solders. Bonding is accomplished bonded below their curie points with acoustically sound interfaces that can transmit sound effectively.  Such piezoceramic based sensors and actuators are used in accurately measuring gas flow and can be used on gas control in MOCVD processes used to deposit and etch computer chips. S-Bond active solders can wet and adhere to most piezoceramics all without pre-plating and chemical fluxes… as such they are finding excellent application in probes and sensors used on semiconductor processing.

Wafers (silicon or other) are placed into energetic plasmas and other beams to deposit then etch a complicated surface morphology in layers to create semiconductor based chips. The high heat energy into the wafer needs to be removed through water cooled wafer handling devices such as the pedestals the wafer sits on in their processing chambers. If not cooled, the interdiffusion of the fabricated on the wafer. With the latest 300mm diameter wafer technology over a $1M work of chips can be on a wafer.

 

 

The high energy levels used in semiconductor processing requires well cooled and reliable handling equipment. S-Bond active solders can intimately join copper and aluminum as well as other thermal management materials such as AlSiC and pyrolytic graphite

If you would like to see how S-Bond active solders can improve your semiconductor processes and handling and measuring equipment, please Contact US.

Sensors and Actuators

Sensors and actuators are a growing commercial market with the Internet of Things (IOT) and the interest to remotely monitor and control many devices.

S-Bond® active solders are finding more application in sensors and actuator devices due to their use of dissimilar materials, including metals, intermetallics, ceramics, composites and glasses which need to be joined. S-Bond® active solders are unique in that they can join such materials, without flux or plating, at low temperatures and with excellent conductivity (both electrical and thermal).

S-Bond® active solders can bond…

  • All metals (Al, Cu, St. Steel, Ti, W, Mo, Ni, etc)
  • Ceramics (Al2O3, SiO2, Sapphire, Quartz, Zirconia, AlN, Si3N4, etc)
  • Carbon / Carbides (SiC, TiC, WC, Graphite, Diamond, etc)

With Ce, Ga and Ti additions to solder filler metals, S-Bond® solders can bond direct to oxides, nitrides and carbides that have formed on metal surfaces, directly. On aluminum and copper the Ga and Ce interact with the oxides that form on these metals then the Sn and Ag constituents form metallurgical intermetallic compounds (IMC’s) that chemically bind the solder to the aluminum or copper base metal. With the active S-Bond® solders’ ability to wet, adhere and join such a diverse set of materials, the S-Bond® alloys find wide application in sensors and actuators that employ a diverse array of materials and in dissimilar material joints… These joints have many requirements, depending on the application, these requirements include…

  1. Thermally conductive
  2. Electrically conductive
  3. Transmits sound
  4. Hermetically seals
  5. Bond strengths high enough for the application
  6. Low temperature joining
  7. Accommodation of CTE mismatch strain

Sensors and Actuators that S-Bond® is currently specified in includes…

Piezo ceramic (PZT) – Ultrasonic Gas Flow sensors; PZT ceramic disks are S-Bond® soldered to stainless steel housings that transmit and receive u/s sound pressure waves. The transmit sensor with bonded PZT piezo ceramic disk sends u/s waves into a passing gas flow and a receive sensor with bonded PZT receives and converts the sound waves… with a shift in frequency known as the Doppler effect, can relate the frequency shift to the mass flow of the passing gas stream. In these sensors, the piezo ceramic disk needs to be intimately bonded with no voids to create an acoustically “hard” transmitting bond interface, joining the ceramic to metal below the curie temperatures of 250 C.  S-Bond® 220 alloys are being used to make these reliable and acoustically sound interfaces.

MEMS Pressure Gages; Silicon based MEMS devices us Si-dies and incorporate circuitry to use the Si as part of the measurement. In the case of pressure measurements, thin diaphragms of Si are created and strain gage circuitry is deposited using lithography to complete the sensor… the challenge then was so seal the Si-sensor die to a metallic pressure housing that is installed onto the component needing a pressure sensor. S-Bond® active solders can join Si direct to metals and can create a hermetic joint, creating a seal between the Si-MEMS pressure sensor and the mounting housing.

Graphite Electrodes / Water Conductivity Sensors; S-Bond® active solders are being used to join graphite to electrical leads for use in Anode/Cathode systems for making excellent electrical solder connections with the use of flux or pre-plating.

 

 

 

Sapphire – Optical Sensors; Sapphire is single crystal aluminum oxide that is very hard/scratch resistant and also transits optical signals in a specific spectrum. As sapphire is an excellent “window” material for many optical signals. For example in Gamma Ray Detection, NaCl single crystal creates photon (light) output proportional to the impinging gamma ray radiation intensity.  The NaCl crystal will degrade/dissolve in contact with air, to the crystal is housed behind a sapphire window which is S-Bond® active solder sealed (hermetic/He leak free) to a titanium tube to create a sealed environment that the gamma rays can penetrate. Optical detectors are then mounted in front of the sapphire window, outside the S-Bond® sealed enclosure.

Insulators /Radar Sensors; Printed 3-D circuits are being made to generate / receive radar signals.  These circuits are built through ceramic layers that form a ceramic backbone to the sensors’ circuitry. S-Bond® active solders have been used to bond the edges of this ceramic backbone of the sensor and seals it from the environment.

Magnet Assemby – Actuators; Magnetic actuators are used to move valves, switches and other devices dependent on precise and reliable stroke based motion. Such magnetic actuators are using high force as CoSm based magnets. These magnets will form a strong and specific magnet fields. In one actuator design, the actuator “rod” runs on the magnet assemblies’ magnetic axis. To assure optimal actuator lineal translation, the actuator’s central push rod could not be magnetic, so it a ceramic rod was selected. In this actuator, S-Bond® active solders have been used to bond the central ceramic rod to the magnetic core of the actuator.

As presented here, S-Bond® solders are being applied in a growing range of sensors and actuators. If you would like to take advantage of S-Bond® solders unique capabilities to join dissimilar materials in your sensors and actuators, please Contact Us.