• Integrated thin film resistor benefits:
  • Increases active component density and reduces form factors.
  • Improves signal routing through elimination of SMT vias.
  • Improves reliability through elimination of solder joints.
  • Shortens cycle times in PCB assembly.
• High speed bus design benefits:
  • Improves line impedance matching.
  • Shortens signal paths and reduces series inductance.
  • Eliminates inductive reactance associated with SMT passive devices.
  • Reduces EMI, crosstalk and noise.
• Resistor stability during thermal excursion:
  • Low temperature coefficient of resistance.
  • Improves resistor tolerance.
  • Long term performance and reliability.
• Utilizes existing PCB processes.
• Uniform isotropic material properties.
• Better than ± 10% resistor tolerances demonstrated after fabrication.
• Laser trimmable to tolerances ±1%.
• Capacity exceeds 1 mm meter²/year.

Overview
Gould developed TCR^® and TCR+™ thin film resistor foil to meet the ever increasing challenges of packaging high speed, high density electronic devices. Integrating passive components into the circuit board using TCR foil can quickly and reliably improve electrical performance and give designers the edge they need. Gould combined well characterized materials from the semiconductor industry with its proven JTC copper foil and proprietary vacuum metallization technologies to provide a robust solution for both designers and printed circuit manufacturers.

For the most commonly used resin systems, TCR is offered with a resistive material applied to the matte side of Doubletreat (DT) or JTCS shiny copper foil using roll-to-roll vacuum deposition technology. For phenolic based and other specialty resin systems, TCR+ is offered with enhanced bonding properties using the same advanced manufacturing methods. The resistive material layer is uniform in composition and deposition thickness ensuring consistent results. Sheet resistance is isotropic and its variation within a roll and between rolls is less than ±5% for all resistance values. The resistive layer is a true thin film with thicknesses from 0.01 to 0.1 µm.

The Grade 3 foil used for TCR and TCR+ is the foil of choice for this application. Grade 3 RTC copper foil exhibits excellent ductility at elevated temperatures, and like standard Gould Grade 3 foils, withstands stresses near the edge of the plated through holes without cracking. These characteristics minimize the need for thermal and mechanical isolation in embedded resistor designs. The treatment on the shiny side copper surface avoids the need for chemical cleaning or mechanical scrubbing, eliminates oxide processing and provides excellent adhesion to prepreg.

Both versions of TCR foil are commercially available today through Gould’s multiple ISO 9001 certified manufacturing locations. Tests by major PCB companies demonstrate consistent and reliable performance.

Advantages

• Versatility – TCR is offered in versions suitable for use on a wide variety of resin systems. TCR+ is optimized to achieve maximum performance when used with specialty resins such as phenolic based systems.
• Greater Uniformity – Thickness of the resistive layer is precisely controlled in Gould’s proven vacuum metallization process. Precision vacuum metallization targets ensure uniform ratios of the elements in the deposited alloy, resulting in minimal resistance variation. The resistance is isotropic and is not dependent on the machine or grain direction of the copper foil or resistive layer.
• Product Performance and Predictability – Gould has gone to great lengths to profile the change in resistance of TCR foil during lamination. The changes pertaining to specific laminate materials and lamination conditions are well understood. This predictability ensures the product provided to our customers is consistent lot-to-lot and sheet-to-sheet.
• Better Resistor Tolerances – Final etch tolerances benefit from TCR’s thin and uniform resistive layer. TCR can eliminate laser trim requirements in all but the most precisely toleranced resistors.
• Reduces Fabrication Steps – TCR with Nickel Chromium (NiCr) resistor alloy reduces fabrication steps by eliminating the need of a separate resistive layer etch. TCR can be etched first in cupric chloride followed by ammoniacal etchant. Use of Doubletreat copper eliminates the need for laminate precleaners and oxide treatments.
• Excellent Thermal Stability – Nickel Chromium and Nickel Chromium Aluminum Silicon (NiCrAlSi) are well known in the semiconductor industry for their excellent thermal stability under continuous load and thermal excursion. The material can be subjected to multiple thermal cycles such as IR reflow with minimal resistance change. The designer and user also benefit from the thermal dissipation properties of TCR foil. NiCrAlSi has improved thermal stability over NiCr and should be considered in applications where thermal stability is critical.

Specifications
TCR Integrated Thin Film Resistor Foil is supplied in a variety of foil widths and thicknesses using Grade 3 copper foil. Thicknesses of 18 µm (0.5 oz) and 35 µm (1 oz) are commonly available. Laminate cores are available with TCR foil on one or both sides using conventional lamination techniques. Laminate substrates such as epoxy and polyimide, as well as a wide variety of high performance substrates, are available with a full range of thicknesses.

TCR • TCR+ Specification Data Set
Resistive Foil Specifications
Resistive material	NiCr	NiCrAlSi
Sheet resistance (/sq)	25, 50, 100	25, 50, 100, 250
Sheet resistivity (%)	±5	±5
Temperature coefficient of resistance (ppm/°C)	<110	-20
Base copper foil thickness (microns)	18, 35	18, 35
Roll width mm (inches)	1295 mm (51")	1295 mm (51")
Maximum recommended power dissipation at 40° C (watts/sq in)	25 /sq: 250 50 /sq: 200 100 /sq: 150 ------	25 /sq: 250 50 /sq: 200 100 /sq: 150 250 /sq: 75
Recommended etching solution
1st etch	Cupric chloride	Ammoniacal*
2nd etch	Ammoniacal	Acidic permanganate
3rd etch	------	Ammoniacal*
For base foil properties, please refer to the appropriate product application sheet. *For NiCrAlSi, cupric chloride can be used in place of ammoniacal etchant.