DIP assembly is an important process in PCB manufacturing for installing and soldering components whose leads pass through holes in the printed circuit board.
Although the term DIP originally refers to Dual In-line Package, it is commonly used in electronics manufacturing to describe a broader range of through-hole assembly operations.
The more technically accurate general term is THT, or Through-Hole Technology.
In a typical DIP assembly process, components are prepared, inserted into PCB holes, inspected, and then soldered using wave soldering, selective soldering, or other suitable methods.
DIP assembly remains widely used for components such as:
- Connectors
- Terminal blocks
- Relays
- Transformers
- Switches
- Large capacitors
- Selected power components
- Certain electromechanical devices
For many industrial, automotive, energy, communication, and control electronics products, SMT and DIP/THT are used together on the same PCB.
What Is DIP Assembly in PCB Manufacturing?
This guide explains what DIP assembly is in PCB manufacturing, how the process works, which equipment is required, and how PCB assembly factories can configure a complete DIP production line.
What Does DIP Mean in PCB Assembly?
DIP stands for Dual In-line Package.
Technically, a DIP component is a package with two parallel rows of leads.
However, in many PCB manufacturing factories, especially in production-line terminology, “DIP assembly” is often used more broadly to describe through-hole component insertion and soldering.
For example, a factory may refer to:
- DIP production line
- DIP insertion
- DIP soldering
- DIP workshop
- DIP assembly process
Even though the components may include connectors, relays, terminals, capacitors, or transformers rather than only dual in-line packages.
For this reason, DIP assembly and THT assembly are often used interchangeably in industrial production discussions, although THT is the broader technical term.
How Does DIP Assembly Work?
A typical DIP PCB assembly process follows several stages.
A simplified production flow is:
PCB Loading → Component Preparation → DIP/THT Insertion → Pre-Solder Inspection → Fluxing → Preheating → Wave or Selective Soldering → Cooling → Inspection → Testing → PCB Unloading
The exact process depends on:
- PCB design
- Component type
- Production volume
- Product mix
- Soldering method
- Automation level
- Quality requirements
Some factories use mostly manual insertion, while others integrate automatic PCB handling and insertion equipment.
PCB Loading
The process begins by loading PCBs into the DIP assembly area.
Depending on production volume, this can be done using:
- Manual loading
- Automatic PCB loaders
- Magazine loaders
- Conveyor systems
For a more automated DIP production line, loaders and conveyors help reduce unnecessary manual handling.
Important factors include:
- PCB dimensions
- Board thickness
- PCB weight
- Conveyor width
- Production direction
THT Component Preparation
Many through-hole components require preparation before they can be inserted.
Component preparation may include:
- Lead cutting
- Lead forming
- Component sorting
- Orientation checking
- Kitting
- Feeding
Typical supporting equipment can include:
- Lead cutting machines
- Component forming machines
- Component preparation equipment
- Feeders
Good component preparation can improve insertion efficiency and reduce operator handling time.
The components are inserted into the corresponding holes on the PCB.
There are three common approaches.
Manual Insertion
Operators insert components by hand.
Manual insertion is suitable for:
- Low-volume production
- High-mix manufacturing
- Complex component varieties
- Frequent product changes
- Components that are difficult to automate
It provides high flexibility but can require more labor.
Semi-Automatic Insertion
Semi-automatic systems assist operators with selected operations.
They can help improve productivity while maintaining flexibility.
Automatic Insertion
Automatic THT insertion equipment can place suitable components automatically.
It is more attractive when:
- Production volume is high
- Products are relatively stable
- Components are standardized
- Packaging supports automatic feeding
Not all THT components are suitable for automatic insertion, so BOM analysis is essential.
Pre-Solder Inspection
After insertion, the PCB should be checked before soldering.
Typical inspection points include:
- Missing components
- Wrong components
- Incorrect polarity
- Incorrect orientation
- Bent leads
- Incorrect insertion depth
- Component position
Detecting errors before soldering can reduce downstream rework.
Flux Application
Flux is applied before wave or selective soldering.
Its purpose is to support solder wetting by preparing the metal surfaces.
Important process factors include:
- Flux type
- Application quantity
- Spray pattern
- Coverage
- Conveyor speed
The goal is controlled and consistent application.
More flux does not automatically produce better solder joints.
Preheating
The PCB is heated before contacting molten solder.
Preheating can help:
- Activate flux
- Reduce thermal shock
- Prepare the PCB for soldering
- Improve process stability
The correct thermal profile depends on:
- PCB thickness
- Copper distribution
- Component thermal mass
- Flux chemistry
- Solder alloy
- Conveyor speed
There is no universal preheat setting for every DIP product.
Wave soldering is one of the most common soldering processes used in DIP assembly.
The PCB passes over a controlled wave of molten solder.
The solder contacts the exposed through-hole leads and pads on the underside of the board and forms multiple joints during the same pass.
Important parameters include:
- Solder temperature
- Conveyor speed
- Wave height
- Contact time
- PCB angle
- Board orientation
- Preheat profile
- Flux application
Wave soldering is especially suitable when many THT joints need to be processed efficiently.
Selective Soldering
Selective soldering is another option.
Instead of exposing a larger PCB area to the solder wave, the machine solders only selected joints or defined areas.
Selective soldering can be useful when:
- The PCB contains only a limited number of THT joints
- There are many bottom-side SMT components
- Certain areas should avoid solder contact
- Mixed SMT/THT designs are complex
- Localized process control is required
The choice between wave and selective soldering should be based on PCB design and target throughput.
Cooling
After soldering, the PCB enters a cooling stage before handling and inspection.
Cooling capacity should be considered as part of the entire line.
If the cooling process is undersized, it can affect downstream production flow.
Post-Solder Inspection
After soldering, the board should be inspected for defects.
Typical soldering problems may include:
- Solder bridges
- Insufficient solder
- Poor wetting
- Incomplete hole fill
- Excessive solder
- Solder icicles
- Incorrect component position
Inspection methods can include:
- Manual visual inspection
- AOI
- X-ray for selected structures
- Electrical testing
- Functional testing
Testing
A finished solder joint does not necessarily mean the PCBA functions correctly.
Depending on the product, testing may include:
- ICT
- Functional testing
- Power-on testing
- Communication testing
- Programming
- Calibration
Testing should be included in capacity planning because it can become a production bottleneck.
What Components Are Commonly Used in DIP Assembly?
DIP/THT assembly is commonly used for components that benefit from through-hole mounting.
Typical examples include:
- Terminal blocks
- Connectors
- Relays
- Transformers
- Switches
- Large electrolytic capacitors
- Power components
- Pin headers
- Fuses
- Certain sensors
- Electromechanical components
These components are frequently found in:
- Industrial control systems
- Automotive electronics
- Power supplies
- Energy equipment
- Communication products
- Home appliances
- Factory automation equipment
- Control boards
Why Is DIP Assembly Still Used?
SMT has become the dominant assembly technology for many modern electronic products, but DIP/THT remains important.
Additional Mechanical Support
Through-hole leads pass through the PCB.
This can provide useful mechanical support for components that may experience:
- Plugging and unplugging
- Vibration
- Mechanical stress
- Pulling forces
Connectors and terminals are common examples.
Suitable for Larger Components
Some large transformers, relays, capacitors, and connectors are better suited to THT mounting.
Useful for Certain Power Applications
Some power-related components use through-hole mounting because of their size, electrical requirements, or mechanical design.
However, THT should not be considered automatically better than SMT.
The appropriate assembly method depends on the product design.
DIP Assembly vs SMT Assembly
DIP/THT and SMT use different mounting methods.
Most modern electronics factories do not need to choose only one process.
They often use SMT + DIP/THT together.
How SMT and DIP Work Together
A mixed PCBA process may follow:
Solder Paste Printing → SPI → SMT Placement → Reflow → AOI → DIP/THT Insertion → Wave/Selective Soldering → Inspection → Testing
SMT is typically used first for:
- ICs
- Resistors
- Capacitors
- Small semiconductor packages
DIP/THT is then used for:
- Connectors
- Relays
- Transformers
- Terminals
- Larger components
This combination allows manufacturers to achieve both high component density and suitable assembly for larger through-hole parts.
What Equipment Is Needed for a Complete DIP Production Line?
A complete line may include:
- PCB loader
- PCB conveyors
- Component preparation machines
- Manual insertion workstations
- Semi-automatic insertion equipment
- Automatic THT insertion equipment
- Inspection conveyors
- Fluxing system
- Preheating system
- Wave soldering machine
- Selective soldering machine
- Cooling equipment
- PCB unloader
- Inspection equipment
- Testing equipment
Not every factory requires every machine.
The equipment list should be based on the actual product.
Recommended DIP Production Line for Low-Volume Production
A flexible low-volume configuration can be:
Manual PCB Loading → Component Preparation → Manual THT Insertion → Inspection → Wave/Selective Soldering → Inspection → Testing
This configuration is suitable for:
- Prototype production
- High-mix products
- Small batches
- Frequent product changes
Its main advantage is lower investment and high flexibility.
Recommended DIP Production Line for Medium-Volume Production
A practical semi-automatic line may follow:
Automatic PCB Loader → Insertion Conveyor → Manual/Semi-Automatic THT Insertion → Inspection → Fluxing → Preheating → Wave Soldering → Cooling → Unloader → Inspection → Testing
This can provide a good balance between:
- Production capacity
- Labor
- Flexibility
- Investment
It is commonly suitable for EMS manufacturers and factories with mixed product portfolios.
Recommended DIP Production Line for High-Volume Production
A higher-automation configuration can include:
Automatic Loading → Automatic/Semi-Automatic THT Insertion → Automated PCB Transfer → Inspection → Fluxing → Preheating → Wave/Selective Soldering → Cooling → Automated Inspection → Testing → Unloading
Additional systems may include:
- Barcode scanning
- Traceability
- Buffers
- MES integration
- Automatic testing
Higher automation should be justified by production volume and product stability.
How to Improve DIP Assembly Efficiency
Improving production output does not simply mean buying a faster soldering machine.
Manufacturers should analyze the complete line.
Identify the Bottleneck
Measure the cycle time of:
- Component preparation
- Insertion
- Inspection
- Wave soldering
- Testing
The slowest stage often limits total production capacity.
Improve Component Preparation
Operators should not spend excessive time searching for, cutting, or forming components.
Balance Manual Workstations
Divide insertion work evenly among operators.
Automate Suitable Processes
Automation should be applied where it creates measurable benefits.
Reduce Rework
Improving first-pass yield can increase effective production capacity.
Standardize Changeovers
Clear product recipes, fixtures, tools, and work instructions can reduce downtime.
Common DIP Assembly Defects
Common issues can include:
Missing or Incorrect Components
Usually related to insertion or material control.
Reversed Polarity
Common with polarized capacitors, diodes, and other directional components.
Solder Bridging
Adjacent solder joints become unintentionally connected.
Insufficient Solder
The joint does not receive enough solder.
Poor Wetting
Solder does not properly wet the lead or pad.
Incomplete Hole Fill
Solder does not sufficiently fill the plated through-hole.
Solder Icicles
Sharp solder projections remain after the soldering process.
A stable DIP process requires control of both insertion and soldering.
How to Improve Wave Soldering Quality in DIP Assembly
Important factors include:
- Component solderability
- PCB condition
- Flux application
- Preheat profile
- Solder temperature
- Conveyor speed
- Wave height
- PCB orientation
- Equipment maintenance
When defects appear, changing solder temperature alone is rarely the best troubleshooting strategy.
The complete process should be reviewed.
How to Choose a DIP Production Line
Before purchasing equipment, PCB assembly factories should prepare key production data.
This includes:
- PCB dimensions
- PCB thickness
- Panel format
- BOM
- THT component list
- Component packaging
- Number of THT components per board
- Target boards per hour
- Daily production volume
- Product mix
- Changeover frequency
- Required soldering method
- Inspection requirements
- Testing requirements
- Factory layout
- Existing SMT/DIP equipment
- Required automation level
- Investment budget
With this information, the DIP line can be designed around real manufacturing requirements.
New vs Pre-Owned DIP and SMT Equipment
Factories can configure a line using new equipment, pre-owned equipment, or a combination of both.
New equipment may offer:
- New machine condition
- Current-generation functions
- Warranty options
- Longer standardization horizon
Suitable pre-owned equipment may offer:
- Lower initial investment
- Faster capacity expansion
- Access to established machine platforms
Pre-owned equipment should be evaluated based on:
- Machine condition
- Configuration
- Maintenance history
- Spare parts
- Software
- Technical support
- Production compatibility
The best purchasing decision should consider total cost of ownership rather than purchase price alone.
DIP and PCBA Production Line Solutions from Fuliu Electronics
Established in 2014, Fuliu Electronics is dedicated to providing customers with high-quality PCBA intelligent manufacturing solutions and services.
With extensive experience in the SMT industry, we specialize in dependable equipment, professional technical support, and complete SMT and PCBA production line solutions.
Our product portfolio includes SMT pick and place machines from Fuji, Panasonic, ASM, Yamaha, JUKI, and Hanwha, together with ERSA reflow ovens from Germany, MagicRay SPI/AOI inspection systems, automatic solder paste printers, supporting PCBA equipment, pre-owned SMT equipment, SMT spare parts, machine leasing, and maintenance services.
For customers planning a new DIP/THT production line or upgrading an existing PCB assembly process, Fuliu Electronics can help evaluate:
- PCB dimensions
- BOM
- THT component types
- Production capacity
- Product mix
- Automation requirements
- Wave or selective soldering
- Factory layout
- Existing equipment
- Inspection and testing requirements
- New and pre-owned equipment options
For mixed-technology production, SMT and DIP/THT processes can also be evaluated together as part of a complete PCBA manufacturing solution.
As part of our global growth strategy, Fuliu Electronics is actively expanding into international markets, with key focus areas including India, Vietnam, the Philippines, Indonesia, the Middle East, South Africa, and Europe.
Conclusion
So, what is DIP assembly in PCB manufacturing?
DIP assembly is commonly used to describe the through-hole assembly process in which component leads are inserted through PCB holes and then soldered.
A typical DIP manufacturing process includes:
Component Preparation → Insertion → Inspection → Fluxing → Preheating → Soldering → Cooling → Inspection → Testing
Although SMT has become the dominant technology for high-density electronics, DIP/THT remains important for many:
- Connectors
- Terminals
- Relays
- Transformers
- Large capacitors
- Switches
- Power components
For many PCB assembly factories, the most effective production strategy is not SMT or DIP, but a properly balanced SMT + DIP/THT process.
The correct DIP production line should be configured according to PCB design, BOM, THT component quantity, production volume, product mix, wave or selective soldering requirements, testing, factory layout, and automation level.
If you are planning a new DIP/THT production line, upgrading an existing wave soldering process, or building a complete SMT + DIP PCBA factory, Fuliu Electronics can help evaluate your PCB dimensions, BOM, THT component mix, target capacity, existing equipment, factory layout, automation requirements, and budget to develop a suitable production solution.
Frequently Asked Questions
DIP assembly commonly refers to the process of inserting through-hole components into PCB holes and soldering their leads on the opposite side of the board.
Technically, THT is the broader term for this type of assembly.
DIP stands for Dual In-line Package.
However, many electronics factories use “DIP assembly” more broadly to describe through-hole component assembly.
Not exactly.
DIP technically refers to a specific package style, while THT refers to the broader through-hole mounting technology.
In production terminology, the terms are often used interchangeably.
Common components include connectors, terminals, relays, transformers, switches, large capacitors, headers, and selected power components.
A typical process is:
Component Preparation → THT Insertion → Inspection → Fluxing → Preheating → Wave/Selective Soldering → Cooling → Inspection → Testing.
No.
Wave soldering is widely used for boards with many through-hole joints, while selective soldering or manual soldering can be more suitable for some products.