pcb design - What do the PCB markings mean? - Electrical …
2012年1月19日 · In addition to that, you will also find other markings on the PCB. These are done by the fab house and are used to show UL certification numbers, UL standards that the PCB conforms to, sometimes showing RoHS compliance, and sometimes even a logo of the fab house. These can be done in silkscreening process, or anti-soldermask processes.
pcb design - What pad hole (drill) size is appropriate for a given ...
On the PCB-3D website they added some extra info: Minimum Hole Size is calculated according to equations below: Minimum Hole Size = Maximum Lead Diameter + 0.25mm (for Level A of IPC-2222) Minimum Hole Size = Maximum Lead Diameter + 0.20mm (for Level B of IPC-2222) Minimum Hole Size = Maximum Lead Diameter + 0.15mm (for Level C of IPC-2222)
pcb - Circuit Board Abreviations - Electrical Engineering Stack …
C stands for capacitor, R stands for Resistor, Q stands for transistor but what are the rest? All of the time I see PCB boards with Components I don't know, and unfamiliar abbreviations on the board. The only site I found on this was this, which has a few, but didn't have many I saw on the board. Is there an official list of circuit board ...
How to choose a spacer/stand-off to maintain electrical contact?
The pillars will provide an earth but this could be unreliable and using crinkle washers onto PCB copper is OK providing you don't fasten and unfasten a few times but whatever mechanical method you choose I don't think there is a substitute for a soldered wire from the PCB joining the chassis plate via a crimp type eyelet - you could even ...
pcb design - Naming (C1, C2, R1, R2...) components on PCB
2012年7月20日 · I like the designators assigned by physical layout on the PCB. This way when looking for R56 you can tell you are getting close when you see R54. But this is also the hardest because it involves back annotating to the schematic. Then the purchasing BOM needs to be redone because the original BOM was created using the schematic.
pcb - QFN Standoff (Solder Joint) Height - Electrical Engineering …
2015年9月5日 · For QFNs at a pitch of 0.5mm and below, keep PCB footprint pad width equal to package pad width. For 0.65mm and above. For QFNs at a pitch of 0.5mm and above, you can define the solder mask between pads. For QFNs at a pitch of 0.4mm and below, define an area that keeps mask out for each row of pads on the QFN. There are many variables here.
How can I add "standoffs" to elevate a SMD component above the …
I made a mistake when creating a symbol/footprint for a small (2.0 x 1.6 mm) SMD crystal and didn't notice until the prototypes didn't work. Unfortunately, the boards are tiny and expensive (0.4 mm
circuits - What does "JA" stand for on this PCB? - Electrical ...
2020年8月5日 · Markings like that are commonly used to indicate where a component goes on the PCB. Usually, the part is marked with some name, "JA-1" in this case, on the electrical schematic. This name is carried over to the PCB layout design as well so designers, layout people, assemblers, anyone working on the device knows what piece goes where.
pcb - Why is the circuit board abreviation for transistor "Q ...
2013年4月25日 · On circuit boards, I see that transistors are "Q", but why Q? Shouldn't "TR" be transformer, so transistor can be "T" because transistors seem to be more common then transformers.
voltage - Minimum clearance between two traces that have a …
2017年8月30日 · The accepted creepage distance depends on the Comparative Tracking Index (CTI) of the pcb material (in the table it is the "material"), on pollution degree, if traces are on the same or different layers, if the required insulation is Basic, Functional, Double (or Reinforced), that depends on the working voltage of the connected circuits, also ...