Through-Hole Assembly Process

Die through-hole assembly process is a traditional but still widely used method in PCB-Montage, where electronic components are inserted into drilled holes on a printed circuit board and then soldered to form strong mechanical and electrical connections. While modern manufacturing relies heavily on SMT-Bestückung, through-hole technology (THT) remains essential for components that require durability, high power handling, or mechanical stability.

Below is a detailed explanation of the through-hole PCB Assembly process.

Overview of Through-Hole Assembly

In through-hole PCB Assembly:

• Component leads are inserted into pre-drilled holes
• Leads pass through the board and are soldered on the opposite side
• Connections are stronger compared to SMT-only designs

This method is commonly used in:

• Power electronics
• Industrielle Ausrüstung
• Connectors and transformers

Angebot für PCB-Bestückung einholen

Through-Hole Assembly Process Flow

A standard through-hole PCB Assembly process includes:

• Component preparation
• Component insertion
• Lead trimming
• Soldering (wave or selective)
• Inspektion und Qualitätskontrolle
• Cleaning and finishing

Each step ensures reliability and structural strength.

Component Preparation

Before assembly begins:

• Components are checked for quality
• Leads may be pre-formed to fit hole spacing
• Parts are organized for efficient insertion

Proper preparation improves assembly efficiency and reduces errors.

Component Insertion

Components are inserted into the PCB:

• Manual insertion: used for low volume or complex boards
• Automated insertion: used in high-volume production

Operators or machines place components into designated holes based on assembly drawings.

Beschneiden von Blei

After insertion:

• Excess leads extending from the bottom of the PCB are trimmed
• Ensures proper soldering and prevents short circuits

This step prepares the board for the soldering process.

Soldering Methods

Wellenlöten

The most common method in through-hole PCB Assembly:

• The PCB passes over a موجة من solder molten
• Solder attaches to exposed metal leads and pads
• Suitable for high-volume production

Selektives Löten

Used for mixed PCB-Montage (SMT + through-hole):

• Solder is applied only to specific areas
• Prevents damage to nearby SMT components

Selective soldering offers higher precision.

Inspektion und Qualitätskontrolle

After soldering, inspection ensures quality:

• Visual inspection for solder joints
• AOI (Automatisierte optische Inspektion)
• X-ray inspection (if necessary)

Checks include:

• Proper wetting
• No cold joints
• No solder bridges

Cleaning Process

If required:

• Flux residues are removed
• Cleaning improves long-term reliability

This step is important for high-reliability applications.

Final Testing

Through-hole assembled boards may undergo:

• Elektrische Prüfung
• Funktionsprüfung

This verifies that the PCB Assembly performs as expected.

Advantages of Through-Hole Assembly

• Strong mechanical bonding
• High reliability in harsh environments
• Suitable for high-power and high-voltage applications
• Better resistance to vibration and thermal stress

Disadvantages Compared to SMT Assembly

• Higher labor cost
• Slower production speed
• Requires drilling holes (higher PCB cost)
• Lower component density

Because of these limitations, through-hole is often combined with SMT-Bestückung in modern designs.

Applications of Through-Hole PCB Assembly

• Industrielle Kontrollsysteme
• Kfz-Elektronik
• Luft- und Raumfahrt und Verteidigung
• Power supply units
• Large connectors and transformers

Through-Hole vs SMT Assembly

Schlussfolgerung

The through-hole assembly process remains a critical part of PCB-Montage, especially for applications requiring strong mechanical connections and high reliability. Although SMT-Bestückung dominates modern electronics, through-hole technology continues to play an important role in mixed assembly designs.

Understanding both processes allows engineers and buyers to choose the right solution for performance, cost, and durability.

Angebot für PCB-Bestückung einholen

Wir helfen Ihnen, Kosten und Produktion zu optimieren. Fordern Sie noch heute ein Angebot für die Leiterplattenbestückung an.
Wir bieten professionelle PCB-Bestückungsdienstleistungen, einschließlich SMT, DIP und schlüsselfertige Lösungen.

✔ NDA verfügbar ✔ Schnelles Angebot innerhalb von 24 Stunden ✔ ISO-zertifizierte Fabrik ✔ PCB & PCBA Service aus einer Hand