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Insulating Films

insulating films

Bus bar laminations reduce inductance. This is achieved by passing current bi-directionally through laminated conductor sheets, thereby cancelling the induced magnetic fields, and the inductive reactance. By laminating the conductors together, separated by only a thin insulator, or insulating film, conductors can be positioned as close as .005” apart, maximizing the mating surfaces of the conductors. By reducing the thickness and increasing the width of the conductors, mating surface geometry can be increased. This significantly reduces inductance and increases capacitance. By increasing the capacitance, the material characteristic impedance can be reduced. This has the effect of ultimately reducing signal noise and conductor crosstalk.


Laminated bus bars come in many types of dielectric coating. Each coating has unique characteristics that can be utilized for specific applications. The table below lists various insulating films, and can help you decide what is required for your design. This is key to maximizing the high-efficiency and high-energy density demands of today’s power conversion products.


Material Continuous Use Temp C° Dielectric Constant
Dielectric Strength ASTM D149
(Volts per ml)
Flammability Rating Characteristics
Epoxy Glass (FR4) 140 4.3 1250 UL 94 V-0 Superior mechanical and dimensional stability
Mylar (PET) 105 3.3 7500 UL 94 VTM-0 Cost effective,tear, chemical,and moisture resistant
Tedlar (PVF) 105 11.0 3500 UL 94 HB Chemical/solvent resistant; good mechanical properties
Teonex (PEN) 140 3.4 5000 UL 94 VTM-0 Higher deflective strength & continuous use temp
Nomex 220 1.6 430-845 UL 94 V-0 Flame resistant, durable
Kapton 400 3.7 5000 UL 94 VTM-0 High temp rating & range stability
Epoxy Powder Coating 130 4.0 800 UL 94 V-0 Flame, moisture resistant; ideal for multiple shapes

With the guidance of a competent laminated bus bar manufacturer, designers and engineers are able to make the right choice in insulating material and conductor (raw or plated copper) thickness. Insulation thickness, type, and construction is a function of the applications temperature, ampacity, environment, and installation techniques.

Kapton on Lamination