IPC-7721(S).pdf - 第26页

remove such contaminants. The best solution is to prevent contamination. Handling Electronic Assemblies If no ESDS markings are on an assembly, it still needs to be handled as if it were an ESDS assembly. However, ESDS c…

damage EOS sensitive components or could cause injury to

personnel. Most ESD specifications also require these poten-

tials to be electrically common. The use of ground fault inter-

rupter (GFI) electrical outlets at EOS/ESD workstations is

highly recommended.

2.1.4 Physical Handling

Care must be taken during acceptability inspections to ensure

product integrity at all times. Table 4 provides general guid-

ance.

Physical Damage

Improper handling can readily damage components and

assemblies (e.g., cracked, chipped or broken components

and connectors, bent or broken terminals, badly scratched

board surfaces and conductor lands). Physical damage of this

type can ruin the entire assembly or attached components.

Contamination

Contamination by handling with bare hands or fingers without

some form of protection causes soldering and coating prob-

lems; body salts and oils, and unauthorized hand creams are

typical contaminants. Body oils and acids reduce solderability,

promote corrosion and dendritic growth. They can also cause

poor adhesion of subsequent coatings or encapsulates.

Lotion formulated specifically for use in solder assembly areas

is available. Normal cleaning procedures will not always

IPC-610-002

Figure 2 Target condition EOS/ESD Workstation

Building Floor

Common

Ground Point

Ground

Personal

Wrist Strap

EOS Protective

Trays, Shunts, etc.

EOS Protective

Table Top

EOS Protective

Floor or Mat

1 M Ohm 10%

IPC-610-003

Figure 3 Acceptable EOS/ESD Workstation

Building Floor

Common

Ground Point

Ground

Personal

Wrist Strap

EOS Protective

Trays, Shunts, etc.

EOS Protective

Table Top

EOS Protective

Floor or Mat

1 M Ohm 10%

Table 4 General Rules for

Handling Electronic Assemblies

1. Keep work stations clean and neat. There must not be

any eating, drinking, or use of tobacco products in the

work area.

2. Minimize the handling of electronic assemblies and

components to prevent damage.

3 When gloves are used, they need to be changed as fre-

quently as necessary to prevent contamination from

dirty gloves. (See Figure 4).

4. Solderable surfaces are not to be handled with bare

hands or fingers. Body oils and salts reduce solderabil-

ity, promote corrosion and dendritic growth. They can

also cause poor adhesion of subsequent coatings or

encapsulates.

5. Do not use hand creams or lotions containing silicone

since they can cause solderability and conformal coat-

ing adhesion problems..

6. Never stack electronic assemblies or physical damage

may occur. Special racks need to be provided in

assembly areas for temporary storage.

7. Always assume the items are ESDS even if they are not

marked.

8. Personnel must be trained and follow appropriate ESD

practices and procedures.

9. Never transport ESDS devices unless proper packaging

is applied.

IPC-7721

Number: 2.1

Revision:

Date: 2/98

Subject: Handling Electronic Assemblies

Page5of8

remove such contaminants. The best solution is to prevent

contamination.

Handling Electronic Assemblies

If no ESDS markings are on an assembly, it still needs to be

handled as if it were an ESDS assembly. However, ESDS

components and electronic assemblies need to be identified

by suitable EOS/ESD labels (see Figure 1). Many sensitive

assemblies will also be marked on the assembly itself, usually

on an edge connector. To prevent ESD and EOS damage to

sensitive components, all handling, unpacking, assembly and

testing must be performed at a static controlled work station

(See Figures2&3).

Avoid contaminating solderable surfaces prior to soldering.

Whatever comes in contact with these surfaces must be

clean. When boards are removed from their protective wrap-

pings, handle them with great care. Touch only the edges

away from any edge connector tabs. Where a firm grip on the

board is required due to any mechanical assembly procedure,

gloves meeting EOS/ESD requirements need to be worn.

These principles are especially critical when no-clean pro-

cesses are employed.

Handling After Solder

After soldering and cleaning operations, the handling of elec-

tronic assemblies still requires great care. Finger prints are

extremely hard to remove and will often show up in confor-

mally coated boards after humidity or environmental testing.

Gloves or other protective handling devices need to be used

to prevent such contamination. Use mechanical racking or

baskets with full ESD protection when handling during clean-

ing operations.

Common Tools and Equipment

Work environments require tools and equipment to conduct

electronic assembly operations. The following information is

provided as guidance regarding the use of common equip-

ment. EIA-625 provides more specific information.

Gloves and Finger Cots

The use of gloves or finger cots may be required under con-

tract to prevent contamination of parts and assemblies.

Gloves and finger cots must be carefully chosen to maintain

EOS/ESD protection.

• Handling with clean gloves and full EOS/ESD protection

• Handling during cleaning procedures using solvent resistant

gloves meeting all EOS/ESD requirements.

• Handling with clean hands by board edges using full EOS/

ESD protection

Figure 4 Target Condition - Class 1,2,3

Figure 5 Acceptable - Class 1,2,3

IPC-7721

Number: 2.1

Revision:

Date: 2/98

Subject: Handling Electronic Assemblies

Page6of8

NOTE: Any assembly related component if handled without

EOS/ESD protection may damage electrostatic sensitive com-

ponents. This damage could be in the form of latent failures,

or product degradation not detectedable during initial test or

catastrophic failures found at initial test.

IPC-2-1-1

Figure 6

IPC-7721

Number: 2.1

Revision:

Date: 2/98

Subject: Handling Electronic Assemblies

Page7of8