4.2 PRINTED CIRCUITS BOARD (LEVEL 1) 4 questions

PCB's for radios and Tv's use?

Copper laminated paper treated with phenolic resin

PCB's which have flame resistant properties use?

Copper laminated paper treated with epoxy resin

PCB's which require good mechanical strength use?

Copper laminated glass silk weave.

Laminate materials reinforced with fibreglass are strong when subjected to mechanical stresses.

PCB's which have circuits printed on both sides use?

Laminated paper for additive processes

Polyester / Teflon / ceramics used for specialised applications require?

The board is completely laminated with copper on ONE or BOTH sides.

"patterning" is what?

The process of converting a circuit diagram into a pattern of connected conductors and spaces for the components

Etching method

The surface begins as a complete layer of CONDUCTING MATERAL (copper) and a pattern is removed by dipping the surface into an ACIDIC SOLUTION.

Addition method

The surface begins as a complete layer of INSULATOR and a pattern is added by dipping the surface into a COPPER PLATING SOLUTION.

Single Sided Board (simple)

components mounted on the REVERSE SIDE.

Double Sided Board (complex)

- WIRING CONTINUED ONTO REVERSE SIDE.

- COMPONENTS MOUNTED BOTH SIDES.

- conducting paths cross one another without connecting.

- LEADS are THROUGH THE HOLE /EYELETS OR FUNNELETS

Multi-Layer Board

- utilise one or more internal conductor planes.

- Disadvantage = the soldering process, as internal planes act as heat sinks.

Flexible curcuits are laminated to what base?

Mylar or Kapton

SMT or (Planar Mounting) Advantages are?

- Smaller parts

- Denser layout

- Cheaper PCBs (no holes to drill)

- Improved shock and vibration characteristics

- Improved frequency response

- Easier to shield from EMI/RFI (Electromagnetic Interference/Radio Frequency Interference)

- Easier to automate manufacturing

Disadvantages of SMT or (Planar Mounting)

- More heat generated

- Small clearance makes cleaning difficult

- Visual inspection difficult

- Good joint formation important for the mechanical .reliability of the assembly

- Harder to hand assemble

Offset pad mounting

variation of the surface mount.

The lead is passed through a hole and is bent so that it can be surface mounted. The join can be some distance away from the hole.

Conformal coatings protect against what?

moisture, humidity, shock, vibration, and corrosion, and provide electrical isolation.

Conformal coatings are applied how?

via spray, dip, brush, or robotic selective systems.

after applying conformal coatings the next step is to?

cure via heat, UV, or room temperature cure mechanisms.

what ways are PCBs or cards are utilised on aircraft?

- Fitted inside boxes or components

- Fitted into rack assemblies or card files

- Fitted into computer rack assemblies