This searchable table brings together 140 markings encountered on PCB silkscreens, schematics, BOMs, and industrial electrical drawings. It mixes component reference designators such as R, C, and U; functional labels such as GND and TP; and legacy or project-specific abbreviations.
Use it as an identification aid, not as a universal standard. A code can mean different things in different companies, CAD libraries, countries, or equipment families. Resolve an uncertain marking against the board schematic, BOM, assembly drawing, and the exact component manufacturer’s datasheet before ordering parts or making a repair.
Meaning of the Different PCB Markings
*Table 1: This comprehensive PCB code list provides 140 circuit board abbreviations and component codes used in electronic design.
| No. | Letters Code | Meaning |
|---|---|---|
| 1 | AAT | automatic power-on device |
| 2 | AC | alternating current |
| 3 | ANT | Antenna |
| 4 | BATT | Battery |
| 5 | BHBM | Temperature measurement sensor |
| 6 | BL | Liquid level sensor |
| 7 | BT1BK | Time measuring sensor |
| 8 | BV | speed changer |
| 9 | C | Capacitor |
| 10 | CN | Connector |
| 11 | D | Diode |
| 12 | DC | direct current |
| 13 | EUI | electromotive voltage current |
| 14 | F | frequency |
| 15 | FB | Ferrite Bead |
| 16 | FET | Field Effect Transistor |
| 17 | FF | Dropout fuse |
| 18 | FL | Filter |
| 19 | FR | thermal relay |
| 20 | FTF | Fast Fuse |
| 21 | FU | fuse |
| 22 | FV | Voltage limiting protection device |
| 23 | G | generator |
| 24 | GDT | Gas Discharge Tube |
| 25 | GND | Ground / Common |
| 26 | HA | Acoustic signal |
| 27 | HB | blue light |
| 28 | HG | Green light |
| 29 | HL | Indicator light |
| 30 | HP | light plate |
| 31 | HR | Red light |
| 32 | HS | Optical signal |
| 33 | HW | White light |
| 34 | HY | Yellow light |
| 35 | IC | Integrated Circuit |
| 36 | J | Jumper / Connector |
| 37 | JK | Jack |
| 38 | JP | Jumper Pin |
| 39 | K | relay |
| 40 | KA | momentary relay |
| 41 | KD | differential relay |
| 42 | KF | flasher relay |
| 43 | KH | thermal relay |
| 44 | KI | impedance relay |
| 45 | KM | intermediate relay |
| 46 | KOF | export intermediate relay |
| 47 | KP | Polarization Relay |
| 48 | KR | Reed Relays |
| 49 | KS | signal relay |
| 50 | KT | time relay |
| 51 | KV | voltage relay |
| 52 | L | Inductor / Line |
| 53 | LED | Light Emitting Diode |
| 54 | M | Motor |
| 55 | MIC | Microphone |
| 56 | MOD | Module |
| 57 | MOV | Metal Oxide Varistor |
| 58 | NC | Not Connected |
| 59 | OSC | Oscillator |
| 60 | PA | Ammeter |
| 61 | PAR | Reactive ammeter |
| 62 | PF | Frequency table |
| 63 | PJ | Active energy meter |
| 64 | PJR | Reactive energy meter |
| 65 | PM | Maximum Demand Meter (Load Monitor) |
| 66 | PPA | Phase Meter |
| 67 | PPF | Power Factor Meter |
| 68 | PR | Reactive power meter |
| 69 | PW | Active power meter |
| 70 | PQS | active and reactive apparent power |
| 71 | Q | circuit switching device |
| 72 | QF | circuit breaker |
| 73 | QS | isolation switch |
| 74 | R | Resistor |
| 75 | REL | Relay (Generic) |
| 76 | RT | Thermistor |
| 77 | RV | Varistor |
| 78 | SA | transfer switch |
| 79 | SB | push button switch |
| 80 | SBE | Panic button |
| 81 | SBP | Pressure switch |
| 82 | SBR | Reverse button |
| 83 | SBS | Stop button |
| 84 | SBT | Test button |
| 85 | SC | Contactor |
| 86 | SCR | Silicon Controlled Rectifier |
| 87 | SE | experiment button |
| 88 | SG | Signal lamp |
| 89 | SL | Level switch |
| 90 | SM | Humidity control switch |
| 91 | SP | Pressure control switch |
| 92 | SPK | Speaker |
| 93 | SQ | Limit switch |
| 94 | SQP | Proximity switch |
| 95 | SR | Reset button |
| 96 | SS | Speed control switch |
| 97 | ST | Temp control auxiliary switch |
| 98 | SV | Voltmeter changeover switch |
| 99 | SW | Automatic transfer switch |
| 100 | T | Transformer |
| 101 | TA | current transformer |
| 102 | TBP | Pressure transmitter |
| 103 | TC | Thermocouple |
| 104 | TF | Temperature limiter |
| 105 | TG | Thermostat |
| 106 | TH | Heater |
| 107 | TM | Temperature transmitter |
| 108 | TP | Test Point |
| 109 | TR | Thermoresistance |
| 110 | TT | Temperature controller |
| 111 | TV | voltage transformer |
| 112 | U | Rectifier / Integrated Circuit |
| 113 | UB | Uninterruptible power supply |
| 114 | UC | Converter |
| 115 | UI | Inverter |
| 116 | UR | Thyristor rectifier |
| 117 | US | Soft starter |
| 118 | UT | Step-down transformer |
| 119 | V | Frequency converter |
| 120 | VC | Control circuit with power rectifier |
| 121 | VR | Variable Resistor / Potentiometer |
| 122 | W | Cable / Wire |
| 123 | WB | DC bus |
| 124 | WC | Control small busbar |
| 125 | WCL | Closing small busbar |
| 126 | WE | Emergency lighting branch line |
| 127 | WELM | Emergency Lighting Small Busbar |
| 128 | WEM | Emergency lighting mains |
| 129 | WF | Flash small busbar |
| 130 | WFS | Accident Sound Small Bus |
| 131 | WIB | Plug-in (feed) bus |
| 132 | WL | Lighting branch line |
| 133 | WLM | Lighting mains |
| 134 | WP | Power branch line |
| 135 | WPM | Power mains |
| 136 | WPS | Forecast audio small bus |
| 137 | WS | Signal small busbar |
| 138 | WT | trolley line |
| 139 | WV | Voltage small busbar |
| 140 | Y | Crystal Oscillator |
Printable 4-page working reference, revised September 2, 2026. Board- and manufacturer-specific documentation remains authoritative.
How are PCB Markings and Component Labels Applied?
Understanding how PCB marking is executed during the manufacturing process is crucial for ensuring durability and readability. Depending on the density of the board and the required precision, several industry-standard methods are used to apply pcb component labels and circuit board markings.
1. Silkscreen Printing (The Industry Standard)
Silkscreen is the most common method for applying a PCB markings guide to a board. It involves pushing specialized ink through a stencil (screen) onto the PCB surface.
Best for: Standard component marking and large logos.
Advantage: Cost-effective for high-volume production.
Limitation: Lower resolution compared to digital methods, making it difficult for extremely high-density layouts.
2. Liquid Photo Imaging (LPI)
LPI uses a process similar to the application of solder mask. A photo-imageable epoxy is coated onto the board, exposed to UV light through a film, and then developed. This provides higher accuracy for pcb board abbreviations and fine lines than traditional silkscreen.
3. Laser Marking (Micro Marking on Electronic Copper)
For high-end or high-density boards, micro marking on electronic copper or the substrate is achieved using high-precision UV or CO2 lasers.
Precision: This method is essential for tracking individual boards with tiny DataMatrix codes or serial numbers.
Durability: Unlike ink, laser-etched circuit board markings are permanent and resistant to harsh chemicals and high heat during the reflow process.
4. PC Marking Thermal Transfer Printing
When variable data is required—such as unique tracking IDs or date codes—pc marking thermal transfer printing is often employed.
The Process: A thermal print head melts a wax or resin ribbon onto a heat-resistant label, which is then applied to the PCB.
Application: Ideal for pcb component labels that need to be updated frequently without redesigning the entire silkscreen layer.
Comparison of Marking Technologies
*Table 2: Comparison of different technologies used for pcb marking and identifying pcb component codes.
| Marking Method | Precision Level | Durability | Best Use Case |
|---|---|---|---|
| Silkscreen Printing | Medium Precision | High | Standard pcb component marking and logos. |
| Laser Etching | Ultra-High Precision | Permanent | Micro marking on electronic copper for high-density tracking. |
| Thermal Transfer | High Precision | Medium | Variable pcb component labels and unique serial numbers. |
| Direct inkjet printing | High Precision | High | Variable legends, serial numbers, and quick-turn production. |
Tips for Reading PCB Markings
Reading the markings on a printed circuit board (PCB) can be daunting at first, but with some practice and basic knowledge of the symbols and codes used, it can become second nature. Here are some tips to help you get started:
1. Learn the basic symbols and codes
Familiarize yourself with the most common symbols and codes used on PCBs, such as component designators, polarity indicators, reference designators, and rating markings. Knowing these will help you understand the information on the board more easily.
2. Read the component labels
Component labels usually include a manufacturer’s part number, a description of the component, and the electrical characteristics of that component. This information will help you identify what type of component is installed on the board and its specifications.
3. Inspect the board closely
Take your time when inspecting the board to look for any signs of damage or corrosion. Look for any solder joints that may have been disturbed, and any components that may have been added or removed from the board. Learning how to identify and fix issues like cold solder joints can be very helpful.
4. Refer to the schematic
If you’re having trouble understanding the markings on the board, refer to the schematic to cross-reference the markings and make sure they match up. This can help you determine if there are any discrepancies between the board and the schematic.
5. Test the components
Once you’ve identified the components on the board, test them to make sure they’re working correctly. This will help you confirm that the board is functioning properly and is free of defects.
6. Read the markings from left to right
When reading a PCB marking, it is important to read the markings from left to right, as this will help to ensure accuracy. This is especially important when there are multiple components in a single line.
7. Look for additional information
In some cases, additional information may be included on the PCB markings. For example, the maximum voltage or current rating of a component may be included. It is important to look for this information in order to ensure that the component is suitable for its intended purpose.
8. Use a reference guide
If you are having difficulty interpreting a PCB marking, it can be helpful to consult a reference guide. A reference guide will provide detailed information about the various symbols and abbreviations used in PCB markings, as well as their meaning.
Frequently Asked Questions about Circuit Board Markings
Q1: What is the most common PCB abbreviations list for components?
R for resistor, C for capacitor, and U for an integrated circuit are common reference-designator conventions, but they are not universal. IPC-2612 addresses electronic diagram documentation and naming conventions; it does not mandate one universal PCB abbreviation table. Confirm the prefix used by the project’s schematic, BOM, assembly drawing, and CAD library.
Q2: How is micro marking on electronic copper achieved?
Micro marking on electronic copper is typically achieved through high-precision laser direct imaging (LDI) or specialized etching. For serial numbers, pc marking thermal transfer printing is often used on heat-resistant labels that are then applied to the board.
Q3: When should PCB labeling be checked?
Before layout release, during first-article inspection, and after any revision that changes parts, footprints, or test access.
How to identify an unknown PCB marking reliably?
First classify the mark: a schematic reference designator, a board-level function or polarity label, a component top mark, a manufacturing trace code, or a certification mark. Each class needs a different source of evidence.
Evidence hierarchy and inspection workflow
*Table 3: Verification guide for different types of markings and codes on PCB components.
| Mark type | Primary evidence | Verification step |
|---|---|---|
| Reference designator | Schematic, BOM, assembly drawing, CAD library | Match the prefix and number to the same board revision |
| IC or component top mark | Exact manufacturer datasheet and package-marking addendum | Use package, pin count, logo, lot/date code, and circuit context together |
| Polarity, pin 1, connector, or test point | Assembly drawing and component datasheet | Confirm orientation electrically before applying power |
| UL or other certification mark | Issuer's official certification database | Verify the file number or unique ID; do not rely on the logo alone |
| Revision or trace code | Fabrication/assembly traveler and change history | Record the code before repair so the correct drawing set is used |
Authoritative references:
- IPC-2612 scope and table of contents – requirements for schematic and logic documentation
- UL Product iQ information – official route for verifying UL certification data and identifiers
PCB labeling review checklist
Review PCB labeling before fabrication release, after the silkscreen and assembly-clearance checks, and again on the first assembled article under magnification.
Practical checklist
- Keep reference designators readable after solder-mask expansion, silkscreen clipping, and component placement.
- Use unambiguous polarity and pin-1 indicators for connectors, diodes, electrolytic capacitors, and IC packages.
- Align test-point labels with the schematic and test procedure so measurements are repeatable.
- Recheck labels whenever the BOM, footprint, connector orientation, or board revision changes.
