The
following guidelines, the second in a series, apply to making your
SMT components "assembly ready" .
The info below continues the
outline we started in our last newsletter corcerning the "best
practices" of designating the polarity of components on the printed
circuit board assembly.
Through-hole SIPs Make sure that the Pin 1 designation
in the silk screen has a bar in between the pads of Pin 1 and Pin 2,
or a dot next to the pad of Pin 1. Pin 1's pad should be square
while the other pads should be round.
Through-hole transistors The emitter pin should be
designated in the silk screen with an "E". It is also a good idea to
outline the part in the silk screen pattern.
Through-hole
batteries Positive pins should have their pads designated with a
"+" in the silk screen. Make sure to make the positive pin's pad
square and the negative pin's pad, round.
Through-hole
canister-type transistors or ICs Canister-type components
usually have a tab on the rim of the can to designate Pin 1. This
tab should be shown on the silk screen to designate the mounting
orientation.
SMT DIPs It is recommended that the silk
screen should include a "1" or a dot next to Pin 1.
SMT
connectors Surface mount connectors should have a "1" in the
silk screen next to Pin 1. Pin 2 or the last pin needs to be
designated to show how the pins are numbered if it is not obvious.
SMT polarized capacitors Surface mount polarized
capacitors should have the positive pad designated with a bar or "+"
in silk screen. The bar designates positive lead.
Through-hole connectors Through-hole connectors should
have a "1" in the silk screen next to Pin 1. All pads of the
connector should be round except for the pad of Pin 1, which should
be square. For connectors with more than one row, Pin 2 or the last
pin of the connector should be designated as to how the pins are
numbered.
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