Technology for prototyping multilayers
The general technique used for prototyping is the
same as that commonly used in the production of
multilayer construction. It is possible to make a few
modifications since prototyping is generally only
used for small and sample runs rather than largescale
series production. Oxidation of the inner
layers and de-smearing of the holes is not
absolutely necessary for prototyping. Best possible
prototyping may be achieved using a suitable
process for bonding and through-hole plating.
Bonding technology for prototyping
The recommendations made by ISOLA for
prepreg 2125 (AT 01), for example, are a main
bonding temperature of 180°C, a main bonding
pressure of 150 N/cm2 and a main bonding time of
60 minutes. The cooling phase in the press begins
when the heating is switched off and the lasts a
minimum of six hours. The long cooling phase
prevents resin smearing during drilling.
Furthermore, the de-smearing process can be
omitted from the through-hole plating process if
prolonged cleaning is carried out during throughhole
plating. The prepreg material RO 44039® for
microwave engineering produced by ROGERS
Corp. can be bonded with other RO 4000 substrates produced by ROGERS Corp or FR-4
material at a main bonding temperature of 180°C, a
main bonding time of 90 minutes and a main
bonding pressure of approximately 300 N/cm2.
Through-hole plating multilayers in prototyping
The use of „direct„ metallization to create the
electrical connection between the various conductor
track layers in the multilayer through holes in the
multilayer is an environmentally friendly process.
Once the holes have been cleaned and coated with
carbon particles or palladium (which have no
impact on the environment), metallic copper is
deposited from a solution of copper salts in sulfuricacid,
to which an electrical current is applied. This
copper acts as a connector element between the
various conductor track layers and as
reinforcement of the external conductor tracks. In
the case of some substrate types, through-hole
plating for microwave engineering can be performed
using the standard process of direct metalization.
Some types of substrate require an additional
etching process as part of the standard direct
metalization process. However, user-friendly
etching processes are available. Prepreg RO 4403
produced by ROGERS does not require desmearing
before through-hole plating. Multilayers
constructed from RO 4403, RO 4003 or RO 4350
can be through-hole plated using conventional
methods.
Cross section of a 6-layer board made with LPKF
prototyping equipment.
Laboratory systems, such as LPKF's MiniContac
and Contac, are available for through-hole plating
multilayer prototypes. These types of systems are
based on the familiar black-hole process and are
very low-maintenance and display long-term
stability. Bath analysis is required once a year only
and these systems make professional multilayer
through-hole plating possible in your own laboratory.
LPKF Laser & Electronics
LPKF Laser & Electronics is a wholly owned
subsidiary of LPKF Laser & Electronics AG of
Garbsen, Germany, a publicly traded company.
Founded in 1976, LPKF has established itself on
the international market in the fields of advanced
circuit board prototyping, SMD stencils and highdensity
circuit board designs, eliminating the need
for hazardous chemicals. Their revolutionary
MicroLine laser circuit structuring processes are
transforming the design of smaller, lower cost,
higher-performance products for
telecommunications, computing, medical, video and
measurement applications.
LPKF high precision circuit board plotters,
multilayer devices and plating systems have
become the standard of the industry with more than
8,000 installations worldwide. The drilling and milling
process is simple, safe and economical. High
precision tools and superior mechanical design turn
circuit designs into holes and traces on a card by
removing material. A typical multilayer card can be
produced within on work day for $15 to $20 in
materials and tools. |
