| | 28.01.2005 | PCB specification for press-fit technology Production of printed circuit boards
that meet the requirements of press-fit technology is extremely important
for a good press-fit connection. The material and structure of a printed
circuit board plated through hole has at least as high an influence on
the quality of a press-fit connection as the press-fit zone itself.
The DIN standard 41 611, part 5, "solder less electric connections
- press in connections" covers the specifications for the structure
of a printed circuit board.
The IPC standard IPC-D-422 contain the design guide for Press Fit Rigid
Printed Board Backplanes.
The decisive characteristic of a high quality press in connection is
not only a final diameter of the plated through hole withing the permissible
tolerances, but also a correct hole structure.
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More about the PCB hole requirements for the press-fit
technology (PCB hole HAL tin, PCB hole copper) you can find here
(de/eng) and here (eng)
| | 28.02.2005 | Hybrid Multilayer PCBs. Base materials made from PTFE (Teflon)
are being used in larger and larger volumes. The reason for it is
based on the continuously increasing operating frequencies of electrical
appliances. The dielectric properties of FR4 are not adequate any
longer to ensure functionality: Dielectric Constant (DK) incl. tolerance,
dielectric loss, etc. The correct solution lies in the use of PTFE
base material, which is manufactured according to applications, even
in Europe.
Multilayers made of PTFE have been virtually unknown until recent
time, but total system cost analyses have changed the rules: Multilayers
made entirely from thermoplastic materials are being used as well
as hybrid multilayers composed of PTFE and FR4 (pls. see lay-up example
http://www.ellwest-pcb.com/solutions.php?year=2003#5
). In all-RF multilayers
thermoplastic bonding films made of CTFE (for instance TacBond HT1.5
bonding film from TACONIC) or FEP are used to bond the inner layers
instead of prepregs. As with FR4 multilayers, increasing packaging
densities of printed circuit boards are the decisive factors. It
is
also possible to obtain coupler structures, whereby PTFE inner layers
of different thicknesses and dielectric constants can be bonded together
(pls. see a picture below)
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More about this matter you can find find
in article of Dipl.-Ing. (FH) Manfred Huschka here.
| | 29.08.2005 | Fungus Resistance – Conformal Coating
Some electronics products require because
of the environmental condition (high humidity and/or temperature, presence
of inorganic salts) applicatioon of such printed circuit boards for theis
construction, which are covered with a special mask resistant against
different kinds of fungi and mould. General requirements for solder masks
for the printed-circuit boards are formulated in IPC-SM-840C
"Standart - Permanent Polymer Coating (Solder Mask) for Printed Boards".
A corresponding test method is described in standart: IPC TM-650 - chapter:
2.6.1.1.“Fungus
Resistance – Conform Coating" - test is to be made for following kinds
of Fungus:
Scientific name:
ATCC code:
Aspergillus niger ....................................9642
Chaetomium globosum ............................6205
Gliocladium virans ..................................9645
Aureobasidium pullulans ..........................9348
Penicillium funiculosum ...........................9644
We can introduce - and apply in our PCB production - fungus resistant
PCB solder masks of manufacturers:
- Peters GmbH & Co.,
KG (Germany)
-
GOO CHEMICAL CO., LTD.(Japan)
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