Rockwell Automation 1336S_F_E_T_R Transistor and Thyristor (SCR) Service - Manual (Page 2)

2 Bulletin 1336 Service
Surface Preparation After removing the transistor or SCR modules from the drive, the heat-
sink and replacement modules must be prepared using the following
method to ensure proper heat transfer and operation of the replacement
components.
1. Remove all old heat transfer compound from the surface of the
heatsink using a tool such as a rubber spatula that will not mar the
heatsink surface. Remove any remaining residue with a soft cotton
cloth and a cleaning fluid such as Essex Cleaning Fluid, Brownell
OS-3 by Dow Corning Co. (Mineral spirits may also be used if
Essex cleaning fluid is not available).
2. Use a non-marring cleaning pad such as a Scotchbrite by 3M TM to
remove any oxidation from the face of the heatsink. DO NOT use
steel wool or sandpaper to clean the surface of the transistor/SCR
baseplate or the heatsink, as they could scratch or score the surface
which will impede heat transfer from the transistor to the heatsink.
3. Follow the oxidation removal with a final cleaning of both the
heatsink and the module baseplate with cleaning fluid and the soft
cloth.
NOTE: Thermal compound must be applied immediately to both sur-
faces as detailed in the following Installation section to prevent oxida-
tion from reoccuring.
If a cleaning agent other than Essex by Dow Corning is used, make
certain it leaves No residue on the heat transfer surfaces.
Installation Install the transistor or SCR module to the heatsink as follows:
1.
Apply a liberal coating of themal compound (AOS 52022) to the
transistor or SCR module base plate using the amount of 6 gram
blister packs (part number 196261) recommended in Table 1 for
your particular device.
2. Apply the thermal compound until the metal surface is no longer
visible. Do not allow any foreign particles or contamination to
collect on the thermal grease. The nominal thickness of the grease
coating should be about 0.005 inches or 0.127 millimeters.
3. Mount the transistor or SCR module on the heatsink, pressing and
rotating in a slight circular motion to better seat the transistor onto
the heatsink and distribute the grease more evenly.
4. Apply slight pressure and attempt to lift the module back off the
heatsink. If the module does not easily separate from the heatsink,
the thermal interface is correct. If the module easily separates from
the heatsink with no suction effect, this could be due to insufficient
grease or foreign particles on either the module base plate or the
!
ATTENTION: This assembly contains parts and sub-
assemblies that are sensitive to electrostatic discharge.
Static control precautions are required when servicing this
assembly. Component damage may result if you ignore
electrostatic discharge control procedures. If you are not
familiar with static control procedures, reference Allen-
Bradley Publication 8000-4.5.2 Guarding Against
Electrostatic Damage, or any other applicable ESD
protection handbook.