Custom vs. Standard Hermetic Packages: Pros, Cons, and When to Go Custom

In high-reliability electronics, packaging is not just a mechanical enclosure—it’s a critical design decision that directly determines product lifetime and performance. Hermetic packages protect sensitive components from moisture, gas, and contaminants that could otherwise compromise functionality. Yet one strategic question repeatedly confronts engineers and OEMs alike: should you use a standard hermetic package or invest in a custom design?

Understanding Hermetic Packaging

A hermetic package is a sealed enclosure designed to block the ingress of air, moisture, or other contaminants for decades. These enclosures rely on metals, ceramics, or glass—materials with extremely low permeability—joined by brazing, glass-to-metal sealing, or laser welding. The result is a structure capable of withstanding extreme environments such as high temperature, pressure, radiation, or vacuum.

Hermetic sealing standards (like MIL-STD-883 and MIL-PRF-38534) specify how leak rates and reliability must be tested. Applications range from aerospace sensors and implantable medical devices to RF modules and photonics. Wherever reliability and longevity are non-negotiable, hermetic packaging is essential.

Defining Standard vs. Custom Hermetic Packages

The distinction between “standard” and “custom” lies in flexibility versus speed.

• Standard Hermetic Packages are catalog or off-the-shelf designs—often TO cans, flatpacks, or ceramic hybrids—already qualified and mass-produced. Vendors maintain inventories, drawings, and test data, allowing rapid procurement and predictable cost.

• Custom Hermetic Packages are tailored solutions built for unique requirements. They may involve new shapes, feedthrough layouts, lid materials, window apertures, internal getters, or specific thermal paths. Every design aspect—geometry, materials, and process—is optimized for the customer’s device.

While the distinction sounds binary, many projects blend both approaches: a semi-custom variant that modifies a standard base to achieve the best of both worlds.

Advantages of Standard Hermetic Packages

Standard hermetic packages remain popular for good reason. They offer proven performance and minimal risk for most commercial and industrial uses.

a. Lower Cost and Lead Time

Because tooling, fixtures, and qualification data already exist, standard packages require no upfront engineering fees. Production and delivery times are short, enabling faster time-to-market.

b. Proven Reliability

Standard packages are already field-tested and certified to military or industrial standards. Manufacturers can rely on well-characterized leak rates, thermal behavior, and electrical performance.

c. Simplified Supply Chain

Catalog items are available from multiple vendors, ensuring continuity and cost stability. Replacement or second sourcing is relatively straightforward.

d. Predictable Performance

Design teams know exactly what to expect—dimensions, pinouts, and sealing behavior are all documented, allowing quicker integration and qualification.

e. Ideal for Moderate Volumes

For small-to-medium production runs, standard packages minimize unit cost without demanding large-scale amortization of tooling expenses.

These benefits make standard hermetic packages the default choice for projects where cost, speed, and qualification simplicity outweigh customization needs.

Limitations of Standard Packages

However, standard solutions inevitably impose constraints.

a. Restricted Design Freedom

Standard geometries and pinouts may not fit compact layouts or non-traditional form factors. Engineers must adapt their circuit design to the package instead of the reverse.

b. Suboptimal Thermal and Electrical Paths

In high-power or high-frequency applications, standard packages may exhibit higher thermal resistance or parasitic capacitance, limiting performance.

c. Unused Volume or Excess Weight

Standard housings can be larger or heavier than necessary, an issue in aerospace or miniaturized medical devices.

d. Limited Material Choices

Available combinations of Kovar, ceramic, or glass seals may not perfectly match the coefficient of thermal expansion (CTE) of the die or substrate, increasing mechanical stress.

e. Fewer Opportunities for Differentiation

Competitors might use identical packages, offering no visual or functional distinction in the marketplace.

When performance or design constraints become critical, these disadvantages motivate engineers to pursue a custom path.

Advantages of Custom Hermetic Packages

Custom hermetic packages allow designers to optimize every parameter for performance, reliability, and aesthetics.

a. Tailored Form and Fit

You define cavity size, wall thickness, and feedthrough positions precisely to fit your die, optics, or sensors—no compromises on space utilization.

b. Enhanced Thermal Management

Custom designs can integrate copper-molybdenum bases, metalized vias, or heat spreaders to achieve superior thermal conductivity and even temperature distribution.

c. Material and CTE Matching

Selecting metals or ceramics with thermal expansion similar to internal components reduces mechanical stress, improving long-term hermeticity.

d. Integration of Specialized Features

Custom packages can incorporate optical windows, RF shielding, getters, micro-channels, or internal coatings that standard housings lack.

e. Long-Term Cost Efficiency

Although initial tooling is expensive, high-volume production amortizes development cost, reducing per-unit price over time.

f. Product Differentiation

A unique enclosure enhances your brand identity, provides IP protection, and can serve as a competitive advantage.

In short, custom packages maximize performance and integration flexibility—especially where the environment, power density, or reliability targets exceed the boundaries of standard designs.

Challenges and Trade-Offs of Custom Designs

Every benefit comes with a corresponding cost.

a. Higher Upfront Investment

Design, simulation, tooling, and prototype validation can be expensive. Non-recurring engineering (NRE) costs may reach tens of thousands of dollars.

b. Longer Lead Time

From concept to qualified production may take months, given design iterations, sample fabrication, and testing.

c. Greater Technical Risk

New materials or sealing methods might introduce unforeseen issues—CTE mismatch, micro-leaks, or warping during brazing. Thorough qualification is mandatory.

d. Vendor Dependence

If only one manufacturer can produce your design, supply-chain resilience becomes a concern. Dual-sourcing or licensing may be required.

e. Regulatory and Testing Complexity

Custom designs must still pass hermeticity, vibration, and thermal shock testing. Establishing new test protocols extends development schedules.

Therefore, custom packaging is most justified for high-performance, high-volume, or mission-critical applications where precision outweighs cost and time pressures.

When to Go Custom: Practical Guidelines

Choosing between standard and custom hermetic packages is ultimately a business-engineering decision. The following factors can guide your choice:

• Environmental Extremes: If your device faces high temperature, radiation, or corrosive media, a custom material combination (e.g. titanium-ceramic) may be essential.

• Performance Demands: For RF, laser, or high-speed digital applications requiring controlled impedance or optical alignment, standard options may be insufficient.

• Size and Weight Constraints: Aerospace and implantable medical devices often need ultra-compact or lightweight housings that catalog parts can’t provide.

• Integration Needs: If your module combines electronics, optics, and fluidics, you’ll need a multi-function package impossible to achieve off-the-shelf.

• Volume and Lifecycle: At high production volumes or over long product lifetimes, custom tooling quickly pays for itself through per-unit savings.

• IP or Brand Differentiation: A proprietary design protects intellectual property and strengthens product identity.

• Regulatory Compliance: In medical or defense markets, custom packaging can help meet specialized standards or documentation requirements.

• A hybrid route is also practical: start with a standard base package and request selective modifications—custom lid, plating, or feedthrough pattern—to gain 80% of the benefit with 20% of the cost.

Design and Qualification Best Practices

If you proceed with a custom design, certain principles ensure success:

• Collaborate Early with Vendors: Involve the packaging supplier at the concept stage to confirm manufacturability and cost.

• Model Thermal and Mechanical Stress: Use finite element analysis to predict deformation, heat flow, and sealing stress.

• Control Internal Atmosphere: Specify getter materials or inert gas backfills to stabilize long-term humidity levels.

• Test Early, Test Often: Conduct prototype leak testing, vibration, and thermal cycling before committing to tooling.

• Plan for Scalability: Ensure the design can be mass-produced consistently within tolerance and budget.

• Document Everything: Maintain drawings, material traceability, and process data to streamline future certification.

By managing these factors, a custom hermetic package can achieve superior reliability without compromising manufacturability.