1. Basic Structure
The VFD is a variation of the Triode Vacuum Tube which is composed of three basic electrodes; The Cathode (Filament), Anode (Phosphor) and Grid under the high vacuum condition in the glass envelope.
The Cathode is a directly-heated fine tungsten wire which is coated by an alkaline earth metal oxide. The Grid is a thin metal mesh. The Anode is a segment or dot formed conductive electrode onto which is printed the phosphor to indicate characters, numbers, symbols or any icons.
Electrons emitted from the Cathode are accelerated with positive potential applied to both Grid and Anode, which upon collision excites the phosphor on the Anode to emit Luminous radiation. The desired luminous patterns can be indicated by controlling the positive or negative potentials on the Grid and Anode separately.

Fig.1 Card-Edge Type	Frame and Hybrid Type
1 GLASS SUBSTRATE(ANODE PLATE) 10 GETTER 2 CONDUCTIVE LAYER 11 FACE GLASS (COVER GLASS) 3 ANODE (BASE) 12 SPACER GLASS 4 INSULATION LAYER 13 EVACUATION TUBE 5 PHOSPHOR (DISPLAY PATTERN) 14 NESA(or ITO) COATING 6 CONDUCTIVE PASTE 15 LEAD PIN 7 GRID MESH 16 MOLD RESIN 8 CONDUCTIVE FRIT GLASS 17 SOLDER 9 FILAMENT(CATHODE) 18 FRIT GLASS

2. Constructions
Three representative constructions of VFD are available from Noritake. Each has its own respective features. The suitability of each depends on the application.

2.1 Frame Type Construction (F-Type)
The Grid Rim, Filament Support and Lead Pins are provided on a single metal frame.
The ends of the Grid Rim are extended to the outside of the envelope, and are formed as lead pins for Grid. The Anode Leads are extended into the envelope to connect with the pads which are placed on the glass substrate. Both ends of the filament are welded to the Filament Support and Anchor with the appropriate tension.
The Frame is assembled with the Face Glass and Glass Substrate(Anode Plate). The Lead Pins are tinned and formed into a suitable shape for PC Board assembly.
FRAME-Types require press formed metal dies for construction. They offer good production yield and high reliability against various environmental conditions.

2.2 Hybrid Type Construction(M-Type)
The Grid is directly mounted onto the glass substrate (Anode Plate) with conductive paste. The Filament and Lead Pins are assembled on the metal frame in the same method as the frame type.
Although the mechanical appearance is very similar to the frame type, the design flexibility provided by having a separate grid structure is greatly improved without losing the productivity yield benefits offered by the frame type.

Fig.13 F-Type Construction Fig.14 Hybrid Type Construction

2.3 Card Edge Type Construction (C-Type)
The Card-Edge type has an unique glass card edge(s). Conductive layers are extended to the card edge and a variety of lead pins or FPC can be connected. This method allows flexible and fine pin out up to 0.5mm pitch. So, in case of high density patterning such as a dot matrix display, FPC may be connected on card edge for fine lead out. If the spacing allows, the grid mesh can be extended to outside directly, see below.
In this construction, it is possible to design VFD flexibly by a lot of standardized tooling and parts. Large size package up to 600mm in length can be designed by this construction.

Fig.15 Card-Edge Type Construction