1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Printed Board Type: N/A
Skill Level: N/A
Conformance Level: N/A
Revision: N/A
Revision Date: N/A

2.1 Handling Electronic Assemblies
Procedure covers the proper methods
for handling circuit boards.

Printed Board Type: R/F/W/C
Skill Level: Intermediate
Conformance Level: High
Revision: E
Revision Date: Mar 27, 2001

OUTLINE
This procedure covers the proper methods for handling circuit boards.

Destructive static charges are induced on nearby conductors, such as human skin, and delivered in the form of sparks passing between conductors, such as when the surface of printed board assembly is touched by a person having a static charge potential. If touched at the right solder joint or conductive pattern, the circuit board assembly can be damaged as the discharge passes through the conductive pattern to a static sensitive component. It is important to note that usually the static damage level for components cannot be felt by humans. (Less than 3,000 volts.) 

Figure 1: Handle components by edges to prevent contaminating leads with skin oil.

ESD/EOS Safe Work Areas
The purpose of an ESD/EOS safe work area is to prevent damage to sensitive components from spikes and static discharges. These areas must be designed and maintained to prevent ESD/EOS damage. 

Handling and Storage Methods

1. circuit board assemblies must always be handled at properly designated work areas.
   
   
2. Designated work areas must be checked periodically to ensure their continued safety from ESD. Areas of main concern include:
   1. Proper grounding methods.
   2. Static dissipation of work surfaces.
   3. Static dissipation of floor surfaces.
   4. Operation of ion blowers and ion air guns.
      
      

3. Figure 2: Always handle circuit boards by the edges.

   Designated work areas must be kept free of static generating materials such as Styrofoam, vinyl, plastic, fabrics or any other static generating materials. 
   
   
4. Work areas must be kept clean and neat. To prevent contamination of circuit board assemblies, there must be no eating or smoking in the work area. 
   
   
5. When not being worked on, sensitive components and circuit boards must be enclosed in shielded bags or boxes. There are three types of ESD protective enclosure materials including:
   
   Static Shielding - Prevents static electricity from passing through the package.
   
   Antistatic - Provides antistatic cushioning for electronic assemblies.
   
   Static Disipative - An "over-package" that has enough conductivity to dissipate any static buildup.
   
   
6. Whenever handling a circuit board assembly the operator must be properly grounded by one of the following: 
   
   
   1. Wearing a wrist strap connected to earth ground.
   2. Wearing 2 heel grounders and have both feet on a static dissipative floor surface.
      
      
7. Circuit board assemblies should be handled by the edges. Avoid touching the circuits or components. (See Figure 2). 
   
   
8. Components should be handled by the edges when possible. Avoid touching the component leads. (See Figure 1). 
   
   
9. Hand creams and lotions containing silicone must not be used since they can cause solderability and epoxy adhesion problems. Lotions specifically formulated to prevent contamination of circuit boards are available. 
   
   
10. Stacking of circuit boards and assemblies should be avoided to prevent physical damage. Special racks and trays are provided for handling. 

Printed Board Type: R/F/W/C
Skill Level: Intermediate
Conformance Level: High
Revision: E
Revision Date: May 8, 2001

OUTLINE
Surface contaminants can significantly effect soldering, bonding, coating and the electrical characteristics of printed board and assemblies. This procedure outlines the cleaning methods for circuit boards and assemblies.

1. The ability of solvent based cleaning solutions to remove flux residue containing polyglycols should be assessed since not all solvent based cleaning solutions will remove polyglycols. 
   
   
2. A deionized water rinse should follow IPA/DI cleaning except that a water rinse for double sided circuit boards with plated through holes may not be required. 
   
   
3. Potable (drinking) water should not be used as a final rinse due to the potential of contaminating the circuit board assembly with chlorine, fluorine and halides.
   
   
4. When automated cleaning is used for assemblies that have been conformally coated, it is important that the cleaning process is compatible with the type of coating used and with any unsealed components. The coating should be checked to ensure that the coating will not be degraded by the cleaning process.

NOTE
To reduce solvent volumes, mixtures of IPA with water and IPA with solvent are available in pressurized containers. The propellants are HFC's. These containers may be fitted with a bristle brush spray attachments for additional cleaning action.

1. Clean the board in an Aqueous or Semi-Aqueous cleaner, or pour approximately 10 ml per 4 square inches of effected area.
   
   
2. Scrub the board vigorously with a continually wet soft bristle brush for 10 seconds. 
   
   
3. Rinse the area with 10 ml per 4 square inches of clean Isopropyl Alcohol to effectively remove all potentially harmful residues. 
   
   
4. Handle the board by the edges and blot the excess Isopropyl Alcohol with clean, lint free cloth
   
   
5. Examine board visually for cleanliness. The use of a black light will help detect contaminants that will fluoresce.
   
   
6. Dry boards in oven, if desired. 
   
   
7. If the boards or assemblies are to be stored before use or coating, remove them from the oven and allow to cool until they can be handled. Place the boards or assemblies into self sealing bags with packages of desiccant.

Printed Board Type: R/F/W/C
Skill Level: Intermediate
Conformance Level: High
Revision: A
Revision Date: May 9, 2001

OUTLINE
Surface contaminants can significantly effect soldering, bonding, coating and the electrical characteristics of circuit board and assemblies. This procedure outlines a batch cleaning process for the removal of the small volumes of fluxes and other contaminants that may contact circuit boards during routine circuit board repair and rework operations. This batch cleaning procedure is not necessarily appropriate for the removal of contaminants used during full assembly operations.

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CAUTION
Aqueous batch cleaning may not always be suitable for removing rosin based fluxes or other contaminants that are not readily soluble in water.

CAUTION
Aqueous cleaning will expose all areas of a circuit board assembly to penetrating water spray. Circuit boards must be assessed regarding damage to coatings and devices that may be sensitive to deionized water.

TOOLS & MATERIALS
Batch Water Cleaning System
Brushes
Deionizing Water Filter System
Gloves
Oven
Wipes

Daily System Setup

1. Check and record the meg ohm reading of the water exiting the deionizing filter tanks. Reading should always exceed 1 meg ohm. Immediately change filter tanks if reading drops below 1 megohm.
   
   
2. With the unit empty, run the batch cleaning system through 3 cycles at the start of each day. Check the following:
   - Water Pressure: 20 PSI +/- 5 PSI
   - Water Reservoir Temperature: 120 to 140

Operation

1. Remove any loose items from circuit boards and place circuit boards in suitable cleaning rack. Circuit boards should be placed within the rack at a minimum 45� angle to ensure proper rinse run off.
   
   
2. Place the rack within the batch cleaning system and run through the cleaning cycle. Cycle temperature and cycle times follow:
   - Wash Cycle Temperature: 120 to 140
   - Wash Cycle Time: 75 to 85 seconds
   - Rinse Cycle Temperature: 120 to 140
   - Rinse Cycle Time: 10 to 30 seconds
   
   
3. Remove the rack and visually examine circuit boards for cleanliness.
   
   
4. Dry the circuit boards in oven, if desired.

Evaluation

1. Visually check board assemblies for any evidence of residual flux or contamination. Clean again if needed.
   
   
2. Check circuit board assemblies for any loose items. Reattach items removed prior to cleaning if needed.