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survey: Include LPKF LDS citation

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@ -617,16 +617,16 @@ inks have high resistance, and can be used to create embedded resistors. The cir
Figure~\ref{hsm_fig_materials_silver_ink} contains a tamper sensing mesh on a lower layer, and a keypad matrix with
carbon contacts on its surface.
Figure~\ref{hsm_fig_materials_gold_lds} shows part of a mesh and a contact created using Laser Direct Structuring, a
technique combining selective activation of a plastic surface using a scanning laser and electroless gold plating. Where
in electroplating electrical current is used to deposit metal atoms on a surface, in electroless plating a series of
chemical reactions is used. Electroplating requires all traces to be electrically connected to form a single electrode,
while electroless plating can be used on the finished circuit. Laser Direct Structuring allows patterning complex
surfaces with fine structures made from metal deposited in a thin layer. In Figure~\ref{hsm_fig_materials_gold_lds}, it
is visible how the trace was created using three parallel passes by the laser. The micrograph also shows the rather
coarse edge structure created by LDS, which is caused by the rough surface left after pulsed laser ablation. The uneven,
thin layer of metallization created by LDS results in mechanically fragile contacts that must be contacted using a soft
material, usually an elastomeric connector.
Figure~\ref{hsm_fig_materials_gold_lds} shows part of a mesh and a contact created using Laser Direct Structuring, an
industrial technique combining selective activation of a plastic surface using a scanning laser and electroless gold
plating~\cite{lpkflaser&electronicsagLPKFLDSLaser2014}. Where in electroplating electrical current is used to deposit
metal atoms on a surface, in electroless plating a series of chemical reactions is used. Electroplating requires all
traces to be electrically connected to form a single electrode, while electroless plating can be used on the finished
circuit. Laser Direct Structuring allows patterning complex surfaces with fine structures made from metal deposited in a
thin layer. In Figure~\ref{hsm_fig_materials_gold_lds}, it is visible how the trace was created using three parallel
passes by the laser. The micrograph also shows the rather coarse edge structure created by LDS, which is caused by the
rough surface left after pulsed laser ablation. The uneven, thin layer of metallization created by LDS results in
mechanically fragile contacts that must be contacted using a soft material, usually an elastomeric connector.
\subsubsection{Connection methods}