Motorola MT512M, Basic Service Manual

Page: 54 / 88

6 - 6 MAINTENANCE
5. Position the heat-focus head over the shield.
6. Turn on the heater and wait for the solder to reflow.
7. Once complete, turn off the heat, raise the heat-focus head and wait approximately one
minute for the part to cool.
8. Remove the circuit board and inspect the repair. No cleaning should be necessary.
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 must take place 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.
* Out of dry package Moisture Sensitivity Level (MSL) 2 : 1 year
2A: 1 month
3 : 168 hrs
Table 6-3 List of MTM800 with Enhanced Control Head moisture sensitive components
Part. No. MSL* Description
5166554A01 3 ADDAG
5109841C71 3 Sirf GPS IC (on GPS option board)
5186988J77 3 JAVELIN
5185956E43 2A FLASH 16MB
5185963A85 3 ABACUS AD9874
5166541A01 3 Patriot ROM3
5189233U61 3 PSRAM 4MB
5199434A01 2 Serial SPI EEPROM