Glossary

AWO = assembly work order
board house = PCB manufacturer
BGA = ball grid array
DRC = design rules check
ERC = electrical rules check
ESS = environmental stress screen (temp, vibe, seal, pressure, radiation, etc)
LDR = light dependent resistor (photoresistor)
LGA = land grid array
NMSD = non solder mask defined, mask opening is larger than copper pad underneath and pad shape defines area pin is soldered, positive "solder mask clearance" (most common)
PDN = power distribution network
PGA = pin grid array
PTH = plated through-holes
schematic = a logical representation of the physical connections and depiction of an electric circuit, not a board layout
SMD = solder mask defined, negative "solder mask clearance"
SMD = surface mount device
SMT = surface mount technology
THT = through-hole technology

Development Cycle

Typically use 3 phases of HW development:

prototype
pre-production (attempt at hitting the real form factor)
production (no mods)

With some "revisions on a theme" projects that were iterations on a previous design, we may go straight to production because the HW was mature.

The CAD process is complex, time consuming, tedious and you'd ofteh rather pay a specialist that's not necessarily an engineer a lower rate to do it. Often the design engineer owns the schematic, and then hands it off to a layout expert that's intimately familiar with the tools. May be comfortable passing ownership of the schematic as well. Consider a two-step change process where the first file has all the stuff to be removed deleted, and the second file has all the new stuff to be added in, so you don't have a single step where double changes are happening and confusion can creep in.

Board Design Best Practices

Tip: I look at a lot of eval boards from various vendors. They mostly have one nasty thing in common: the lack of a big ground pin. It's common to connect an instrument to these boards, like a scope, but where will you clip the probe's ground lead? Some have ground available in a 0.1 x 0.1 header, which is great for a logic analyzer connection, but less so for an alligator clip. When designing a board provide at least a nice through-hole via where one can solder a wire (I use an RC07 resistor) to provide a nice big ground. - Ganssle

EDA Tools

KiCAD is an open source tool heavily supported by CERN. Eagle is a simple, limited-use tool in its free form now developed by Autodesk and now has ransomware attributes.

Links

In 2020, I finally found the tutorial for ver 5.1: https://forum.kicad.info/t/tutorial-introduction-to-pcb-design-with-kicad-version-5-1-getting-started/20600/3

Layout FAQ: https://forum.kicad.info/t/what-is-the-meaning-of-the-layers-in-pcb-new-and-in-the-footprint-editor-kicad-5-and-earlier/9688

Using KiCAD

Schematic shortcut keys:
a - add component
c - copy
e - edit
g - grab+move (symbol AND wires)
m - move (just the symbol)
r - rotate
v - edit value
x - flip horiz
y - flip vert
del - delete

Layout shortcut keys that differ from above:
v - via
x - routing tool

50 mils is recommended grid pitch

Design Rules

Define the design rules, manufacturing and electrical. Usually this is done before the layout is created.

In Pcbnew, use File->Board Setup.

What is "restring" measure? This is a component of the through-hole diameter, "minimum copper restring". The via diameter is computed by: ```via drill size + 2 * restring```

Name Equivalency Chart minimum mask land width = solder mask minimum width
minimum drill also applies to minimum via drill
are track and trace interchangeable?

Basic Workflow

The schematic is done with the EESchema tool.

Place symbols
Connect wires
Verify connections visually with highlight net tool
When you are done building, Annotate the parts
Run ERC (electrical rules check)
Then Footprint all your components

The layout is done next with the Pcbnew tool.

First, Update from schematic and place the layout
Organize the footprints/placement
Draw board outline with graphic line tool
Add traces with Route Tracks tool, with insertion of zones and vias as needed
Run DRC and address issues
Adjust design rules if corrections needed (board setup, then edit trace/via properties)

Prepare the Gerber files In Pcbnew, use File->Plot to use the Plot action and then generate drill files.

Labels

global labels = connected across all sheets
power symbols = also act as global
local labels = connected if on same sheet
hierarchical labels = defines interface to a hierarchical sheet

Test Point Options

TODO - place links here

Board Manufacturing

The colors of the PCB are known as solder mask colors.

Always send back and front mask layers even for a one-layer board, so manufacturer doesn't get confused.

The inner layers are numbered, but the top and bottom aren't. For example, a four-layer board would be a sandwich like:

top layer
layer 1
layer 2
bottom layer

Connectors

SMA (SubMiniature version A) connectors are semi-precision coaxial RF connectors developed in the 1960s as a minimal connector interface for coaxial cable with a screw-type coupling mechanism. The connector has a 50 Ω impedance.