Mixed Technology PCB Assembly

Combining SMT & Through-Hole for Superior Performance and Reliability

Modern electronic devices require compact structures, high-density component placement, and long-term durability especially in demanding industrial and mission-critical applications. Mixed Technology PCB Assembly provides the best of both worlds by integrating Surface Mount Technology (SMT) and Through-Hole Technology (THT) on a single board. This hybrid approach offers unmatched design flexibility, electrical performance, and mechanical strength.
Sierra Assembly specializes in Mixed Technology PCB Assembly for industrial, automotive, aerospace, medical, consumer electronics, and IoT applications. With advanced equipment, refined soldering processes, and strict inspection standards, we ensure every hybrid assembly meets the highest levels of performance, consistency, and reliability.

What Is Mixed Technology PCB Assembly?

Mixed technology PCB assembly merges SMT components (such as ICs, resistors, capacitors, LEDs, BGAs) with THT components (like connectors, large power components, relays, transformers) on the same circuit board. Each technology offers unique benefits:

• SMT: High component density, compact size, lightweight design, high-speed placement
• THT: Strong mechanical anchoring, excellent for large or high-power components

By combining both, designers can optimize functionality without compromising size or durability. This makes mixed technology ideal for complex, rugged, or high-performance electronic products.

Why Choose Mixed Technology PCB Assembly?

1. Greater Design Flexibility

Mixed technology assembly allows engineers to place high-density SMT components on one or both sides of the PCB while using  where mechanical support or high current flow is required. This enhances layout freedom and improves overall performance.

2. Superior Mechanical Strength

THT components provide reliable anchoring, making them suitable for:

• High-vibration environments
• Power electronics
• Automotive and aerospace systems
• Industrial machinery

This ensures long-term mechanical stability and durability.

3. High Component Density

SMT allows tight placement of miniature components, enabling:

• Compact device footprints
• Lightweight designs
• High-speed digital circuitry
• Multi-functional PCB layouts

Mixed technology is especially useful in devices where space is limited but performance demands are high.

4. Cost-Effective & Scalable Production

Sierra Assembly supports:

• Rapid prototypes
• Medium-size production batches
• High-volume automated runs

Mixed technology eliminates the need for multiple boards by combining everything into a single, optimized PCB reducing development and assembly costs.

Our Mixed Technology PCB Assembly Process

✔ Step 1: DFM & BOM Review
We begin with a detailed review of your design files to ensure manufacturability and cost-effectiveness. Our engineers evaluate:

• Component placement constraints
• Hole size and tolerance
• Thermal distribution and balancing
• Soldering sequence optimization
• Mixed-technology interaction risks

This reduces rework, shortens lead time, and improves reliability.
✔ Step 2: SMT Assembly
Our SMT process is fully automated for precision and consistency.
Process steps include:

• Solder paste printing with laser-cut stencils
• High-speed pick-and-place of SMT components
• Reflow soldering with optimized thermal profiles
• 3D SPI and AOI inspection

We support advanced SMT components such as:

• Micro-BGAs
• QFNs and DFNs
• 0201/01005 passives
• RF modules
• Fine-pitch ICs

✔ Step 3: Through-Hole Assembly
THT components are inserted and soldered using one of three techniques, depending on design needs:

• Wave soldering – Best for high-volume THT insertion
• Selective soldering – Ideal for boards with mixed SMT and THT regions
• Hand soldering – Perfect for specialized, sensitive, or unique components

Each method ensures strong, reliable solder joints suitable for high-vibration and high-power applications.
✔ Step 4: Cleaning & Inspection
After assembly, PCBs undergo cleaning to remove flux residues. Our quality control includes:

• AOI (Automated Optical Inspection)
• X-ray inspection for BGAs and hidden joints
• Flying probe testing
• ICT (In-Circuit Testing)
• Functional testing based on customer requirements

All assemblies follow IPC-A-610 Class II or Class III standards, depending on project needs.