JAAPSON(www.jaapsonpcb.com)
offers two types of gold finish: Electroless Nickel Immersion Gold (ENIG) as a
surface finish for the whole PCB, and hard plated gold over plated nickel for
edge-connector fingers. Electroless gold gives excellent solderability, but the
chemical deposition process means that it is too soft and too thin to withstand
repeated abrasion. Electroplated gold is thicker and harder making it ideal for
edge-connector contacts for PCBs which will be repeatedly plugged in and
removed.
We
plate the hard gold onto the PCBs after the soldermask process and before we
apply the surface finish to the rest of the board. Hard-gold plating is
compatible with all the other surface finishes we offer.
We
first plate 3 – 6 microns of nickel onto the edge connector fingers and then on
top of that 1 – 2 microns of hard gold. The plated gold is not 100% pure; it
contains some cobalt to increase the wear-resistance of the surface.
We
normally bevel the edge connectors to ensure easy insertion. Bevelling can be
specified in the order details.
To
make sure that the gold fingers align exactly with the edge-connector profile,
we rout the vertical edges of the connector on the first drill run. The edges
of the connector are then exactly aligned to the printed image.
In
some cases one or more gold fingers are shorter than the rest, so that the
longer pads connect first when the PCB inserted into the connector. This means
that the shorter pads cannot be connected vertically to the plating bar. They
have to make the connection needed for electroplating in another direction (see
illustration. Here the blue lines represent the profile added at first drill
stage and the green the final profiling).
Limitations of the technology
The
plated pads have to be on the edge of the PCB, as this is an electroplating
process. There has to be an electrical connection between the plated pads and
the production panel frame.
The
maximum length of the plated pads is 40 mm as we use a standard shallow plating bath .
Inner
layers have to be free of copper at the edge of PCB. Otherwise the bevelling
could expose the copper.
If
you want your PCBs delivered in a customer panel, the panel frame/border must
be open on the edge connector side to allow us to make the connection for
electroplating.
We
can plate hard gold on two sides of PCB. But if the connectors are on the
opposite sides of the PCB there has to be a minimum 150 mm between them.
To
ensure optimum quality surface-finish, do not place any plated holes (PTH), SMD
or other pads closer than 2.00 mm
(80 mil) to the gold fingers – see drawing.
Baggio WANG
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SHENZHEN JAAPSON TECHNOLOGY CO LTD
Building 2, Tongfuyu Industrial Park,Shenzhen, China, 518104
Tel: 86-755-82596922
Fax:86-755-82596922/82596923
skype: baggiowang0214
JAAPSON, The Expert in HDI Multi-layer PCBs
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