Introduction to ESD Trays

ESD stands for “electrostatic discharge”. This refers to the sudden flow of electricity between two electrically charged objects.

In the electronics industry, ESD can be extremely damaging to sensitive components such as integrated circuits, semiconductors, and printed circuit boards. An discharge as small as 30V can brick delicate electronics.

ESD trays help protect electronics from such discharges during manufacturing, storage, and shipping. They are conductive trays that safely drain static charges away from contents.

This article provides an in-depth overview on ESD tray uses including:

• Protecting components from electrical damage
• Maintaining integrity of sensitive electronics
• Enabling safe PCB assembly workflows
• Standard testing and classification
• Proper handling and precautions

Let’s explore the critical role ESD trays serve for mitigating electrical discharges.

The Hazard of ESD Damage

To understand functions of ESD trays, it’s important to first recognize hazards posed by electrostatic discharges:

Permanent invisible damage – While certain ESD events cause immediate product failures, even smaller discharges can incrementally degrade performance and longevity. This builds up “latent damage” challenging to recognize.

Lower reliability – ESD weakens electronic components, leading to premature field failures under thermal/mechanical stresses.

Financial losses – Damaged goods must be scrapped or trigger warranty returns. For products already shipped, replacement is expensive. Either scenario hurts profit margins.

Table below summarizes losses across the supply chain:

Table 1: ESD causes financial losses across the electronics supply chain

So while ESD safety is often an afterthought, in aggregate such preventable damage introduces major costs. Trays help mitigate risk.

How ESD Trays Work

ESD trays protect contents through a conductive surface that safely channels electrical charges to ground. This prevents static building up then suddenly discharging through sensitive components.

Figure 1: ESD trays safely drain charges away components.

Various standards dictate acceptable resistances that allow sufficient charge drainage without impeding functionality. Common requirements:

• Surface resistance: Under 10^9^ ohms
• Volume resistance: 10^4^ to 10^6^ ohms
• Grounding: Via wrist strap or conductive table mat

With proper use, ESD trays form a safe ecosystem protecting electronics from static discharges throughout handling and shipping.

Next let’s explore popular tray applications.

Common Uses of ESD Trays

Major uses of ESD trays fall into three main categories:

1. Protecting Sensitive Components

Vulnerable small items like integrated circuits, sensors and memory chips often ship in ESD trays or bags. Trays conveniently organize such tiny parts for storage or PCB population while safeguarding their integrity.

Figure 2: Trays protect vulnerable ICs, resistors, capacitors etc.

For prototyping, reusable trays avoid waste compared to single-use bags. They simplify organizing a spectrum of parts during development.

2. PCB Assembly Workflows

Entire populated or bare PCB assemblies are also commonly handled in ESD trays:

Figure 3: Trays enable safe handling through assembly.

This protects vulnerable boards through:

• Transport between work centers
• Storage between process steps
• Protection from mechanical damage

Trays are mandatory when working with high frequency or exposed high density boards.

3. Shipping Protection

Finally, ESD trays are ubiquitous for packing electronics distribution:

Figure 4: Shipping protection with foam-lined trays

They enable safe transportation in two ways:

1. Drain harmful static charges
2. Shield components from physical impacts

Various foam liner materials facilitate snug component fit too.

In summary, ESD trays serve needs across electronics workflows – protecting during transportation, storage, and handling.

Next we’ll explore classifications and testing procedures.

ESD Tray Types, Testing and Standards

Not all ESD trays provide equal protection. Various testing procedures help classify trays based on capabilities to mitigate different ESD threats.

Major metrics include:

Surface resistance – Measures ease by which charges dissipate across tray surface. Too high allows static to accumulate.

Volume resistance – Evaluates conductivity through tray’s structural layer. Important for dissipating charges in embedded items.

Decay time – Assesses how quickly exterior surface neutralizes after charge removal.

Charge Shielding – Measures exterior fields with interior item statically charged.

Many industry and military standards now define adequate thresholds levels for tray compliance. Common ones include:

• ANSI/ESD S20.20
• IEC 61340-5-1
• MIL-STD-1686

Below shows a typical classification system:

Table 2: ESD Tray Classification per ANSI/ESD S20.20

So industry groups standardize tray testing to help engineers select appropriate protection levels. This enables matching risks posed by electronics with necessary mitigations.

Now let’s cover proper handling and precautions when using ESD trays.

Proper ESD Tray Use

While ESD trays provide a first line of defense for electronics, following best practices ensures their effectiveness:

• Use wrist straps – Workers must wear grounded wrist straps to avoid accumulating charges.
• Employ table mats – Conductive table mats drain charges from equipment like tools.
• Ground trays – Ground points between trays and mats equalize potentials.
• Avoid overloading trays – Overstuffed trays inhibit proper charge drainage.
• Watch tray materials – Some plastics accumulate high static charges.
• Control humidity – Low humidity enables static to build up.

Adhering to such mitigations is equally important as the trays themselves. Failing to ground personnel and their workstations creates safety gaps.

It’s also good practice to confirm tray condition periodically via resistance testing. Worn trays with degraded surface coatings lose their efficacy over time.

Let’s recap some key points.

Conclusion and Summary

• ESD trays use conductive surfaces to safely channel electric charges away from sensitive electronics to protected ground points. This prevents static accumulating then suddenly discharging through components.
• They serve critical needs protecting electronics across applications in component storage/shipping, PCB assembly workflows, and product distribution.
• Industry standards dictate adequate resistances for charge dissipation without impeding functionality. Testing procedures classify trays accordingly.
• Proper handling techniques including wrist straps, table mats and grounding are vital for trays to be effective. Failing to ground personnel undermines protections.

In essence, ESD trays form the backbone protecting electronics as they traverse global supply chains. Without mitigating such routine electrical threats, achieving acceptable yields and reliability would prove impossible.

Frequently Asked Questions

How do ESD trays work?

ESD trays use a conductive surface to safely channel electric charges away into ground points. This prevents static building up then discharging suddenly through sensitive electronics.

What electronics use ESD trays?

Integrated circuits, PCB assemblies, and finished electronic products all commonly rely on ESD trays while handling through assembly workflows or shipping distribution channels.

What causes ESD tray degradation?

Excessive use leading to surface scratches can degrade conductive coatings over time. Periodic resistance testing checks for worn trays needing replacement. Low production humidity also accelerates decline.

Are some plastics highly charging?

Yes, materials like polyethylene and PVC accumulate extremely high static levels and should be avoided for ESD tray construction unless using specialized additives.

How does humidity impact ESD trays?

Low humidity enables static to build up more easily. Maintaining production area humidity over 40% better facilitates charge dissipation across ESD trays into protect ground points.