Why use thick film?

Advantages of Thick Film Hybrids
over
PCB's

  • Higher precision on resistors. Resistors on PCB's are mounted whereas on thick film hybrids they are printed, fired and trimmed to any value, therefore they can be more precise and can be smaller size.

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High Precision Hybrid

  • Highly accurate active circuit calibration after assembly can be performed to achieve precise performance.
  • Higher reliability due to fewer solder interconnections and a higher metal interconnection reliability than solder joints.
  • Wider operating temperature range. This is due to the ceramic having an excellent thermal rating and heat dissipation capability.
  • Smaller size, exceptionally compact (approximately half the size of the most complex PCB), hybrids are an efficient way of packaging. Hybrids have a higher packing density. The printing of resistors and capacitors enables the thick film hybrid to be smaller in size than the PCB. Resistors can be printed under other mounted components.

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Compact Hybrid

  • Fully encapsulated for protection from the environment.  Hence tolerant to moisture, vibration, corrosion and heat build up.

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Encapsulated Hybrid

  • Since a hybrid is a component it can be burnt in, heat soaked or otherwise qualified to a higher reliability level.
  • Circuits are fully tested. Testing of the circuits is throughout the entire assembly process whereas PCB's are tested at the completion of assembly.
  • A modular technology for complex systems which gives benefits of reliability and maintainability.
  • PCB's require mounting in a box. Thick film hybrid modular components can be encapsulated in an epoxy block which forms the box. This can be a major cost saving.

 

Overview of the Characteristics of PCB's  & Thick Film Hybrid Technologies
The following table indicates thick film hybrids have somewhat higher material and setup costs than PCB's but competitive overall costs, combined with the advantages of superior reliability, tolerances, accuracy, security, performance and smaller size.

ATTRIBUTE

STAINLESS STEEL THICK FILM HYBRID

CERAMIC THICK FILM HYBRID

PRINTED CIRCUIT BOARDS

1. Set up costs

AUS$2,000-$5,000

AUS$2,000-$5,000

AUS$1,000-$3,000

2. Unit costs

Stainless steel is much smaller than PCB, therefore use less of it.

Ceramic size is much smaller than PCB, therefore use less of it.

Raw material of PCB’s is lower cost.

3. Size

Up to 100mm x 100mm but it is generally 50% of the most complex PCB’s.

Up to 100mm x 100mm but it is generally 50% of the most complex PCB’s.

Up to 500mm x 500mm.

4. Components

Fewer components required as the resistors are printed.

Fewer components required as the resistors are printed.

Large components can be mounted onto the board.

5. Reliability

Excellent

Excellent

Good

6. Tolerance to:

a. Temperature

 

-50oC to +100oC

 

-50oC to +100oC

 

-20oC to +85oC

b. Moisture

Encapsulated - Good

Encapsulated - Good

Potential problem

c. Vibration

Encapsulated - Good

Encapsulated - Good

Potential problem

d. Heat build up

Excellent - better than ceramic

Excellent

Not good

e. Corrosion

Encapsulated - Good

Encapsulated - Good

Potential problem

7. Security

Much more difficult to reverse engineer even if encapsulation is removed.

Much more difficult to reverse engineer even if encapsulation is removed.

Can be readily reversed engineered.

8. Accuracy

Can use more precise resistors and can be precision calibrated for high accuracy.

Can use more precise resistors and can be precision calibrated for high accuracy.

It depends on accuracy of components purchased.

9. Functional Modularity

Excellent - The hybrid includes the box.

Good - Boxes are much smaller.

Poor - PCB's need to be mounted in boxes.

10. "Real World" Integration

Excellent - Stainless Steel hybrids as "real world" sensors of strain, flow, pressure, humidity, etc. can be integrated with microprocessor technology to create a single "bolt on" unit.

Good - Ceramic hybrids can include sensor elements however mechanical attachment is limited.

Poor - PCB's need to be connected into the "real world" via separate sensor transducers.

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924 Mountain Highway,
Bayswater Victoria 3153  Australia

Ph: 61 3 9729 2177  Fax: 61 3 9729 8014

E-mail: hybrid@hybrid-electronics.com

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