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Prototyping
LTCC Prototype Manufacturing

IMST GmbH is working since 1996 in the development of multilayer LTCC modules for mm- and microwave applications. LTCC is considered as a key technology for multichip modules starting at a few hundred MHz to about 30 GHz (standard LTCC) or higher. In 2000 IMST has installed a prototype manufacturing line, so that the services modelling, circuit and module design, manufacturing and characterisation can be offered to customers and partners. The final volume production will be carried out from a LTCC foundry. Consequently IMST's process is compatible with the foundrie's one. The following lists summarize IMST's capabilities in multilayer module fabrication and the highlights for microwave applications. This is followed by a detailed description of the process steps.

Summary of IMST's manufacturing capabilities:
  • Standard LTCC-Systems from DuPont, Ferro, Heraeus, ...
  • Substrate Size: 3.5" x 3.5", 3" x 3", 2" x 2"
  • Cavities and Windows
  • Thermal Vias
  • R, L and C Integration (Buried Components)
  • High Resolution Conductors (with Partners)
  • Zero or unconstrained Sintering (with Partners)
  • Post-Processing: Inspection, Soldering, Bonding, Dicing, RF-Characterisation


Highlights of LTCC for microwave applications:

  • Integration of Antenna-, R-, L- und C-Elements
  • High Density of Connections (3D-Design)
  • Cost effective Manufacturing by parallel Process Steps and Reduction of SMD-Components
  • Robust against: mechanical Stress and high Temperatures
  • TCE close to Semiconductor Material: good Integration
  • Potential in RF-frequency Applications
  • Packaging Capabilities in LTCC

Design

The design of multilayer circuits for RF applications requires simulation, modelling and layout tools, which are all available at IMST. A long time experience in working with these software tools and in designing RF circuits and antennas in LTCC has grown to a comprehensive expertise in this field. Furthermore specific design and modelling software has been developed by IMST. These tools are called "EMPIRETM" and "MultiLibTM for ADSTM". IMST's experience is offered to design RF modules and antennas for customers applications ...
Preparation

The LTCC tapes will be delivered on rolls or as sheets in a specific format. The standard sizes, which will be processed at IMST's technology are (in inches) 3.5"x3.5", 3"x3" and 2"x2". These squares will be cut from the tape or roll. In the next steps, the coupons will be pre-conditioned in the furnace at about 80°C followed by cutting registration and via holes with the YAG laser. All manufacturing steps will be made under clean room conditions ...
Via and Cavity Forming

A YAG laser will be used to cut the registration and via holes (> 100µm) out of the LTCC tape. Arbitrary shapes of cavities and windows can be formed with the laser, too ...
Via Filling

The via holes will be filled with thick film pastes using the screen printing method. An accurate alignment of the stencil and the tape can be achieved with an optical positioning system combined with the screen printer. The EKRA printer M2TM fulfils these demands and is used in IMST's LTCC process ...
Screen Printing

Two screen printers are available to print the thick film pastes into via holes or on the surface of the green LTCC tapes. The smaller one is used for less accuracy while the second printer is for high alignment better than 10µm, equipped with an optical alignment system and computer controlled. Both Systems are from EKRA: S15TM and M2TM ...
High Resolution Lines

For high frequency applications an improved conductor resolution is sometimes mandatory. Standard line width and spacing for screen-printing starts at about 100µm. With a photoimageable paste a 50µm resolution can be achieved for conductors in inner layers or on the top or bottom of the laminated structure. Such a system is offered from DuPont and is called FODELTM ...
Collating and Stacking

In volume production each layer is processed in parallel up to this step. After via filling and conductor printing all layers will be collated with a special tool and will be fixed together to avoid misalignment. Collating and stacking can either be carried with a hand operated tool for standard precision or with an automatic stacking machine for high alignment accuracy. IMST's prototyping process allows three different LTCC coupon sizes (unfired): 3.5" x 3.5", 3" x 3" and 2" x 2" ...
Lamination

IMST has installed a versatile isostatic pressing tool. In contrast to the uniaxial method, a higher quality especially when cavities are used, can be achieved. In this process step the lamination system IL-4004 from PTC is used at a typical temperature of 80°C and a pressure of 3000 psi ...
Co-Firing

The laminated LTCC stack will be fired in a computer controlled furnace. The firing will follow a specific profile, which shows a slow rising of the temperature to burnout the organic. Then the temperature is increased up to 870°C, where the sintering takes place. Afterwards, the oven is cooled down. In a free sintering process the LTCC is shrinking up to 13% in X- and Y-direction and up to 15% in Z-direction (thickness) ...
Post-Processing

A number of post-processing steps are offered for the LTCC prototype manufacturing: post-firing of conductors and resistors, surface mount technology and wire bonding, dicing, singulation or sawing and the inspection of the LTCC module. This includes an optical check and a measurement of the geometry under the microscope as well as a high frequency characterisation ...
Characterisation

LTCC (and also other) modules can be characterised at IMST. For RF circuits measurement equipment is available to determine S-parameters, noise behaviour, power, harmonics, spectrum, inter-modulation and load-pulling up to highest GHz-frequencies. For antenna measurements and EMC testing three anechoic chambers and an out-door range are available. Qualified staff will carry out these demanding measurements. All testing facilities are accredited laboratories ...
Production

The goal of the LTCC prototype manufacturing is to offer fast, accurate and reliable module fabrication with LTCC materials from standard suppliers like DuPont, Heraeus, Ferro and others. Moreover, the IMST-process will be adjusted to those foundries, where the volume production will take place. That means, that our process has to be compatible to the fab's process and that an early consolidation and co-operation will take place ...

LTCC Prototyping has been launched in
IGEL: A Project of the Wireless Competence Initiative of NRW.

©2001-2014 IMST GmbH, Last update: 10-Mar.-2006