MAINTENANCE MTH800 TETRA Handportable Terminal / Basic Service Manual 6 - 3
Pre-baking of Integrated Circuits
Electronic components are generally coated with plastic material which has the
nature of not being waterproof. If kept unsealed, the components can absorb
humidity. When soldered to the board (especially with reflow techniques), the
sudden change in temperature can cause fissure or crack which can result in
malfunction or damage.
To avoid this problem, these moisture sensitive components (MS) should be
stored and shipped in a sealed wrapping (dry pack). Processing is not required
only with “dry components” when an uninterrupted dry storage can be
guaranteed, otherwise the components have to be pre-baked.
If a reflow procedure takes place close to MS components, the whole board
must be pre-baked.
Refer to the table below.
Baking Precautions for TETRA Power Amplifiers (PAs)
PAs in an open reel after baking should be used within 168 hours. After 168
hours the PAs must not be used until baked again. Because this is quite a short time,
use at least two reels for each build: one on the machine, and the other still in baking.
After 168 hours the reel on the machine should be replaced with the freshly baked
reel. It is recommended to order a sufficient reserve of PAs, so that at least two reels
will be available in each build.
In addition, please note the following very important precautions that must be
observed when baking TETRA PAs before builds:
P/N MSL DESCRIPTION
5104932K08 3 Tomahawk
5186988J77 3 Javelin
5108683Y54
or equivalent
3 TETRA PA, U901
5116650H01 3 GCAP3 2.4
5166541A01 3 Patriot ROM3
5115443H01 3 LNA-Life
5187512V01 3 Half-Life
5185941F11 3 PSRAM
5185956E43 3 FLASH 16M
5189378V12 3 EEPROM
5188450M52 3 SiRF GPS IC
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