Hidden or buried via: neither ends of the via are visible on either surface; the via transitions signals
entirely between internal layers only.
Unfortunately a 6-layer board is much more expensive than a 2-layer board; and if you use blind or
hidden vias the costs escalate even more drastically. For this reason, no blind or buried vias are
used in the QMX. It is necessary to use a 6-layer board, but the design is not so complex or
compact that blind or buried vias are needed.
NOTE: the capacitor lead spacing on the PCB is 0.1-inches (2.54 mm) and most of the capacitors
are sized appropriately for this. From time to time, due to availability constraints, we may have to
use capacitors with 0.2-inch lead spacing (5.08 mm); this is not a mistake, it is just due to
component availability. In this case simply use a pair of long-nosed pliers (etc) to straighten out
the wires and make them spaced for the 0.1-inch pads.
Board structure
The QMX PCB is on a single panel, which must be broken apart very carefully into smaller pieces.
Do not lose any of the pieces, some of which are quite small. Take great care not to damage any
of the small boards. The following page shows a diagram of the PCB panel, with the
constituent parts outlined in red.
The easiest way to break out the boards is to use needle-nosed pliers or wire-cutters, grab each of
the breakaway tabs colored in yellow, and gently twist it to remove it from the panel, leaving only
the wanted small PCBs. The rough edges must be filed flat carefully, taking care not to
damage any nearby SMD components, particularly applicable to the small power supply
boards. The tiny control board spacers don’t particularly need the rough edges filed.
The large PCB panel supplied is broken out into the following pieces:
• LCD board: This is the top board of stack, the LCD module is bolted and soldered to it.
• Controls board: breaks out of the LCD board, holds the rotary encoders and buttons
• Controls board spacers: two tiny boards, also part of the LCD board; these are very
important to obtain the correct height of the controls board; be careful not to lose them!
• Main board: the main PCB of the QMX with most of the components, on both sides.
• Power supply boards: two PCBs that have the 5V and 3.3V buck converters, reverse
polarity protection, soft power switch, and 3.3V linear regulator. The board shapes are
irregular, be careful not to break any small protrusions.
• Keyfob: QRP Labs fashion: break this out, file the edges smooth, and put it on your key-
ring; enjoy your QRP Labs keyfob with pride
QMX assembly Rev 1.00e 7
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