ProCenter CTR101-1
Manual Supplement
MS-CTR101-1
Page 1 of 1
Issue Date: June 2003
Comco ESD Control ProCenter
CTR101-1
Abrasive blasting tends to cause electro-static charging of the target areas of the work piece, and charge
fallout over other areas. The charging currents are at most a few nano-amperes but can produce very high
voltages on small objects. For electronic circuit boards the charging currents are generally not a problem. If
these currents cause high voltages to be built up and the resulting charged area sparks to other parts of the
board, damage may, and probably will, occur.
The ESD Control model of the Comco ProCenter employs features that help reduce the danger of
electro-static charge build up, sparking, and damage to the work pieces.
HOW IT WORKS:
The ESD Control ProCenter is equipped with a 48-emitter ionizer bar which uses a small amount of
compressed air to produce a balanced, laminar sheet of air to carry static eliminating ions to the work area.
The pressurized air is passed by an air knife under the ionizer emitters, flooding the work area with highly
ionized air that quickly neutralizes surface charges. This ProCenter also contains facilities for nozzle and
work piece grounding, and static dissipative floor panels.
The ionized air system is only effective with the ProCenter turned on and air flowing out of the
air knife under the ionizer emitters. Never blast on sensitive parts when the unit is turned off.
Do not blast inside the chamber without air flowing out of the air knife. Abrasive particles
could migrate into the air passage slit of the air knife and clog it.
The board edge-connector grounding bar (WS2023) should be used to ground all edge pins on boards that
have edge connectors. This device is made of a conductive rubber material and connected through a 1-
megohm resistor to a banana plug that should be plugged into one of the grounding receptacles located at the
right rear corner of the work chamber area. It is recommended that as many connectors as possible on the
target board be grounded.
The needle probe (WS2021) is used to pierce through the conformal coating to ground a target trace when
the defect is known to be an open trace with no conductive path to ground. The abrasive blast can quickly
charge an open section of trace to voltages high enough to break down the insulation and spark to other
traces, or across the defect. The spark currents can be very high and cause damage. The ionized air can
neutralize the field by depositing a lot of charge on the outside of the coating, but this still leaves a
dangerously charged trace. The needle probe provides a solution in the special case where a batch of
boards with this type of known defect must be repaired.
A grounded handpiece assembly (WS2030-2) with a conductive nozzle is provided with the ESD Control
ProCenter. Always use the grounded handpiece and conductive nozzle. Some abrasives can build up an
electrical static charge in the handpiece. Proper grounding of the nozzle and handpiece will reduce the
charge on the abrasives and prevent an electro-static charge from being built up in the nozzle and operator
and arcing to the target area of the work.
GUIDELINES FOR USING THE ESD CONTROL ProCenter:
1.
It is essential that the frame of the ProCenter be electrically grounded, either through well-
grounded electrical conduit, or by heavy copper wire connecting the frame to a water pipe.
2.
Always close the ProCenter loading door before blasting.
3.
Always make sure air is flowing through the air knife before blasting.
4.
Ground as many connectors on the board as possible.
5.
If possible use an abrasive that produces low charging.
6.
Always use a grounded handpiece and nozzle.
7.
The use of operator grounding devices is recommended.
8.
Observe good board handling procedures both in and out of the ProCenter.
