Overview

The two main structural designs for EMI shielding covers are one-piece (Deep-Drawn Shield) and two-piece (Clamshell Shield). Each design has advantages and disadvantages. The choice depends on performance requirements, cost budget, assembly process, and rework strategy.

This article provides a comprehensive comparison to help you make the best choice.

Structural Design Comparison

One-Piece Shielding Cover

Structure: Formed in one operation using deep drawing process, creating a completely closed conductive shell with no seams or joints.

• Bottom is a solder pad (soldered to PCB)
• Vertical walls on all sides
• Top is completely sealed (with optional EMI vents)

Advantages:

• No contact resistance: Monolithic structure with no contact surfaces between frame and lid, optimal shielding performance
• Minimum height: No lid thickness required, saves 1-2mm of space
• High shielding reliability: Not dependent on contact springs, no rework-induced shielding failure risk

Disadvantages:

• Cannot be opened: Internal components cannot be replaced or repaired later, no rework support
• High forming difficulty: When depth exceeds 4mm, prone to wrinkles or fractures
• Slightly higher cost: Requires high-precision tooling and process control
• Long production cycle: Each order requires custom tooling

Two-Piece Shielding Cover

Structure: Consists of a frame and lid. Frame is soldered to PCB, lid is quickly installed via latches, spring contacts, or magnetic attachment.

• Frame: Solder pad + vertical walls, permanently soldered
• Lid: Complete or vented top component
• Connection method: Latches (most common), spring contacts, or magnetic

Advantages:

• Reworkable: Lid can be removed, internal components quickly replaced or repaired
• Production flexibility: Frame soldering can be mass-produced, lids customized as needed
• Low initial cost: Frame tooling can be reused for multiple lid heights/sizes
• Standardized solution: Industry-standard design, mature supply chain

Disadvantages:

• Slightly lower shielding performance: Frame-to-lid contact surfaces create contact resistance, resulting in 5-10dB shielding loss
• Higher overall height: Lid thickness required (typically 2-3mm), increases total height
• Rework-induced failures: Repeated assembly/disassembly can damage latches or springs, reducing shielding performance
• More components: Lid and springs increase assembly complexity

Detailed Performance Parameter Comparison

Cost Analysis

One-Time Investment

• One-Piece: Higher tooling cost (RMB 30,000-80,000), requires specialized deep-drawing tooling. However, per-unit cost is relatively low.
• Two-Piece: Frame tooling is relatively standard (RMB 10,000-30,000), lid tooling is flexible (can share frame tooling). Overall investment is lower.

Per-Unit Cost (1,000+ units)

• One-Piece: Material cost RMB 2-4, processing cost RMB 3-5, total RMB 5-9.
• Two-Piece: Frame cost RMB 1.5-3, lid cost RMB 1-2, spring cost RMB 0.2, total RMB 3-5.

Conclusion: Two-piece has lower per-unit cost, but one-piece may be more cost-competitive for very large volumes (>500,000 units).

Application Scenario Recommendation Matrix

Quick Decision Process

Step 1: Determine Shielding Performance Requirements

• SE < 70dB (consumer electronics) → Two-piece can satisfy
• SE 70-80dB (5G <6GHz) → Two-piece or one-piece
• SE > 80dB (millimeter-wave) → Favor one-piece

Step 2: Evaluate Space and Cost

• Limited height (<5mm clearance) → One-piece
• Adequate height (>8mm clearance) → Two-piece (more economical)
• Cost-sensitive (>100,000 units) → Conduct cost-benefit analysis

Step 3: Consider Rework Requirements

• Rework/upgrade needed → Two-piece is required
• One-time product → One-piece is optional

Step 4: Evaluate Production Capability

• Large stable orders → One-piece investment can be recovered
• Small batch/prototyping → Two-piece scales quickly

Common Misconceptions and Pitfall Avoidance

Misconception 1: One-Piece Always Has Better Shielding

Fact: At frequencies below 1GHz, if two-piece has sufficient grounding points and reliable contact, the difference can be controlled to 3-5dB. This is adequate for most consumer applications.

Misconception 2: Two-Piece Is Always Cheaper

Fact: For ultra-high volumes (>500,000), one-piece per-unit cost may be lower. However, considering tooling cycle and risk, two-piece remains more flexible.

Misconception 3: Contact Resistance Can Be Ignored

Fact: Two-piece shielding loss is primarily due to contact resistance. Must ensure spring contact pressure, contact area, and contact point count are adequate.

Summary and Recommendations

There is no absolute “best” choice, only “most suitable.” For most consumer electronics applications, two-piece is the first choice because it balances performance, cost, flexibility, and reworkability. One-piece is suitable for high-end products with extreme shielding or space requirements.

We recommend communicating with EMI shielding cover suppliers early in product development for performance simulation and cost estimation to find the optimal solution.