Emc; General; Bb Component And Control Io Line Protection; Keyboard Lines - Nokia NKC-1X Series Technical Documentation Manual

CCS Technical Documentation

EMC

General

The EMC/ESD performance of NKC-1X 's baseband is improved by using a shield to cover
the main components of the BB, such as the UEM, UPP and Flash. The UEM has internal
protection against a ±8kV ESD pulse in most sensitive pins and ±2kV in other pins. The
BB-shield is soldered to the PWB and it also increases the rigidity of the PWB in the BB
area, thus improving the phone's reliability. The shield also improves the thermal dissipa-
tion by spreading the heat more widely.
The BB and RF shield are connected together on the PWB and the protective metal deck
underneath the battery is grounded to RF shield.

BB Component and Control IO Line Protection

Keyboard lines

ESD protection for keyboard signals is implemented by using separate EMI filter compo-
nent located between keyboard and UPP. EMI component is a low-pass filter with ±15kV
ESD protection. Also the distance from A-cover to PWB is made longer with the spikes in
the keymat together with C-cover metallization is protecting keyboard lines.

C-Cover

The C-cover on the UI-side is metallized on the inner surface (partly) and is grounded. All
areas in which the plated C-cover touches the PWB surface are grounded and the solder
masks are opened.

PWB

All edges are grounded on both sides of the PWB and the solder mask is opened in these
areas. The aim is that any ESD pulse faces the ground area first when entering the phone,
for example, between the mechanics covers.

LCD

ESD protection for LCD is implemented by connecting the metal frame of the LCD into
ground. The connection is only on one side, at the top of the LCD, which is not the best
solution. The software takes care of the LCD's crashing in case of an ESD pulse.

Microphone

The microphone's metal cover is connected to the GND and there are spark gaps on the
PWB. The microphone is an asymmetrical circuit, which makes it well protected against
EMC.

EARP

The EARP is protected with C-cover metallization and with a plastic-fronted earpiece.

Buzzer

PWB openings with the C-cover metallization protect the buzzer from ESD.
Issue 1 02/03
Nokia Corporation
NKC-1X
System Module
Page 25