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What Is DIP Soldering? A Comprehensive Guide

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The reliable electrical connections of almost all electronic devices are inseparable from soldering. Soldering involves using fusible metal alloys (traditionally tin-lead alloys, but now more often lead-free alloys) to fix and connect electronic components to the PCB. The alloy melts when heated and solidifies after cooling, firmly binding the components electrically and mechanically together. It can be said that without soldering, there would be no today's various electronic products, regardless of which industry they belong to.
 
Different production requirements lead to different soldering processes, such as SMT soldering, DIP soldering, reflow soldering, and wave soldering, etc. And today, what we are going to introduce is DIP soldering. Next, we will elaborate on the relevant content of DIP soldering, including its definition, process, advantages and disadvantages, quality control, and comparison with SMT soldering, etc.
 

What Is DIP Soldering?

 

DIP soldering


DIP soldering is an assembly process specifically designed for dual in-line package (DIP) components. It is a traditional but very reliable method. The process involves inserting the pins of the DIP packaged component into the pre-drilled through-holes on the PCB and then securing them with solder. This process can be carried out manually or with the help of a DIP soldering machine. In mass production, automatic DIP soldering machines (such as wave soldering machines) are commonly used to increase efficiency.

 

DIP soldering is a typical through-hole technology. Unlike surface mount technology (SMT) which directly solders components onto the board surface, DIP soldering can provide stronger mechanical bonding force and higher reliability. Nowadays, due to the demand for miniaturization, SMT is used more frequently, but DIP soldering is still indispensable. This is because it has high mechanical strength and can withstand large currents and high voltages. These advantages are indispensable for equipment in fields such as automotive electronics, power equipment, industrial control, aerospace and military. Here is a detailed comparison table between DIP soldering and SMT soldering.

 

Aspect

DIP Soldering

SMT Soldering

Component Package Type

Dual In-line Package (DIP), leads inserted into holes

Surface Mount Device (SMD), mounted directly on pads

Mounting Method

Leads are inserted into PCB through-holes and soldered

Component terminals are soldered directly onto PCB pads

Soldering Process

Mainly Wave Soldering or manual soldering

Mainly Reflow Soldering

Solder Joint Location

Formed on the opposite side of the PCB, high mechanical strength

Formed between component and pad, small size

Equipment Required

Wave soldering machine, manual soldering station

Reflow oven, pick-and-place machine

Circuit Density

Limited by through-holes, lower routing density

No through-holes needed, supports high-density routing

Mechanical Strength

Strong, suitable for large components (capacitors, transformers, connectors)

Weaker, suitable for small and lightweight components

Application Scenarios

Power boards, automotive electronics, large industrial equipment

Smartphones, computers, wearables, high-speed circuits

Main Disadvantages

Larger space usage, complex routing, lower automation

Weaker solder joints, prone to defects like tombstoning/bridging, harder to rework

Typical Defects

Excess solder, cold joints, insufficient solder

Tombstoning, bridging, cold joints

Advantages

Strong solder joints, high reliability, good mechanical stress resistance

Compact size, supports high-density design, excellent for mass automation

 

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DIP Soldering Process

 

The DIP soldering process is a structured method. The overall process for soldering all DIP components is the same. Below, we will introduce it to you step by step.

 

1. Preparation Work

 

DIP components


Before starting the DIP soldering process, we must first prepare the PCB and the corresponding components. Then, we need to conduct a corresponding inspection on the circuit board. We must check whether the hole diameters are correct, the coating quality is qualified, and the cleanliness is adequate. This is the first step to ensure the reliability of the subsequent solder joints on the circuit board. The components also need to be inspected. We must check the polarity and orientation of the components, especially for components like ICs, diodes, and electrolytic capacitors. In addition, if it is manual soldering later, then we need to prepare an electric soldering iron, flux, and solder wire; if using a DIP soldering machine, such as wave soldering, for soldering, then we need to set up the flux sprayer, preheater, and tin bath. Finally, but equally important, we must take safety and static protection measures.

 

2. Component Insertion

 

After the preparatory work is completed, the component insertion process can be carried out. The correct placement of components is crucial. Components should be inserted into the pre-drilled PCB holes and should be closely attached to the surface of the circuit board to ensure better consistency in the flow of solder. It is also important to note that for some components, their pins need to be pre-formed to match the pitch and be gently bent before soldering to fix the component. During the insertion process, it is best to follow the sequence from lower components to higher ones. This can reduce mechanical stress and shadow effects during the soldering process.

 

3. Soldering

 

After all the components are inserted, it's time for the soldering process. For prototype production, small batch manufacturing, or repair work, we can perform manual DIP soldering directly. Using a temperature-controlled soldering iron to heat both the pads and the component pins simultaneously, and then adding solder until a smooth and shiny solder joint is formed. This manual soldering method is flexible and precise, but it is slower and requires skilled operators. 


wave soldering


For large-scale assembly, we often choose to use a wave soldering machine. The circuit board will go through three stages: flux coating, preheating, and the contact of the solder wave. As the solder wave melts, it will come into contact with the exposed pins and pads, thereby forming uniform solder joints between the circuit board and the components. This method is the preferred choice for through-hole assembly in large-scale production.

 

4. Lead Trimming and Cleaning

 

Lead Trimming


After the soldering is completed, we need to trim the excess component pins to the appropriate length (usually keeping 0.5 - 1.0 mm above the solder joints). This ensures that the produced circuit boards are safer, more reliable and more standardized. Then, depending on the type of flux used, the circuit boards should be cleaned. The water-soluble flux residues can be rinsed with deionized water, and the rosin-based residues can be removed with isopropyl alcohol. Do not forget to clean them, as cleanliness is extremely important. Residues may affect long-term reliability and interfere with subsequent conformal coating and other processes.

 

5. Inspection and Quality Control

 

The final step is rigorous inspection and quality control. Each solder joint must be evaluated in accordance with the IPC-A-610 standard. Key criteria include smooth solder joints, adequate wetting of pads and pins, sufficient hole filling rate, and absence of common defects such as bridging, cold soldering, or gas pores. For non-compliant solder joints, they can be re-soldered by applying flux for repair to restore reliability.

 

Advantages of DIP Soldering

 

One of the major advantages of DIP soldering is that the mechanical connection it forms is extremely strong. When the component pins are inserted into the through-holes of the PCB and the soldering is completed, the molten solder will surround the entire pin. This design not only ensures reliable electrical connections for the circuit board, but also enhances its mechanical strength. This advantage makes DIP soldering particularly suitable for products that are frequently operated, easily subject to mechanical impact or vibration.

 

DIP soldering


Another important advantage of DIP soldering is that it can withstand greater current and voltage. The contact area between the DIP through-hole solder joints and the component leads is larger, so it can carry higher currents without overheating or aging. Power devices such as transformers, relays, capacitors, and power transistors often use the DIP soldering process for soldering.

 

In terms of repairability, DIP soldering also has obvious advantages. When maintenance or servicing is needed, ordinary soldering tools (such as soldering irons or desoldering machines) can be used to easily remove and replace the through-hole components. In contrast, surface mount components, especially those with fine pitches or ball grid array packages, require specialized rework equipment and technicians. In comparison, DIP soldering is indeed convenient and economical.

 

Furthermore, in harsh working environments, DIP-soldered circuit boards can also exhibit extremely high reliability. Due to its larger solder joints and the fixed method of the through-holes, it can effectively resist thermal expansion and contraction, so it is less likely to fail even after repeated heating and cooling cycles.

 

Limitations of DIP Soldering

 

Although DIP soldering has obvious advantages in terms of reliability and strength, it still has some limitations.

 

Firstly, the cost of DIP soldering is usually higher. In traditional processes, DIP components usually require manual insertion and soldering, which poses a challenge to production efficiency. Even with the use of automated wave soldering machines or automatic DIP soldering machines, additional dedicated equipment and processes are still needed. While the SMT production line can complete the entire soldering process by machines. For mass production, compared to SMT, the cost of DIP soldering is much higher.

 

DIP soldering


Secondly, DIP components will occupy more PCB space. Because the pins of DIP components need to pass through the circuit board, holes must be drilled for each pin during design. This not only increases the difficulty of PCB routing but also expands the overall board area. Compared to SMT components, DIP soldering cannot achieve high-density wiring and device arrangement within a limited space. In modern electronic products with extremely high requirements for circuit board thinning, this limitation is particularly obvious. This is also the fundamental reason why DIP soldering is gradually being replaced by SMT in the consumer electronics field.

 

Applications of DIP Soldering in Electronics

 

Although SMT soldering is the mainstream in modern electronic manufacturing, DIP soldering is still an indispensable soldering process in many fields that have strict requirements for reliability and mechanical strength.

 

1. In the automotive electronics field, many modules need to handle large currents and operate in harsh environments for a long time. For example, engine control units (ECUs), power distribution modules, and ignition control systems. These modules must use DIP soldering technology because the DIP soldering method enables the circuit board to have a strong mechanical bonding force and the ability to carry large currents.

 

Applications of DIP soldering


In addition, as mentioned earlier, DIP soldered circuit boards can also exhibit extremely high reliability in harsh environments. This is very important for some modules in automotive electronics. Because during vehicle operation, these modules will undergo intense vibrations and temperature changes, and DIP soldering provides reliability that ensures these critical modules can operate stably for a long time.

 

2. In the power electronics field, DIP components are the core part, and DIP soldering is undoubtedly indispensable. Components such as transformers, relays, power adapters, and power transistors are usually large in size and require stable electrical paths during operation. And the DIP soldering technology can firmly fix these devices on the circuit board while ensuring that they will not fail due to poor contact in high-current and high-voltage environments.

 

3. In industrial automation equipment, reliability and durability are crucial. Many control circuit boards, PLCs, motor controllers, and sensor interfaces still use DIP soldering technology. Due to the presence of dust, moisture, and electromagnetic interference in industrial environments, the DIP structure with through-hole solder joints can better resist environmental factors and ensure the long-term stability of the system.

 

4. In the military and aerospace fields, electronic equipment must remain stable and reliable under extreme conditions. Aircraft, satellites, military radars, and weapon systems all require circuit boards to be able to withstand high temperatures, intense vibrations, shocks, and strong radiation environments. The strong mechanical fixation and stress resistance provided by DIP soldering are among the reasons why it has become a common process in these highly reliable applications.

 

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Quality Assurance in DIP Soldering

 

Not all DIP solders result in secure and reliable solder joints. During the soldering process, in order to ensure the firmness and reliability of the soldered joints, strict quality control measures must be implemented during the production process.

 

The most typical problems that may occur in DIP soldering include cold solder joints, solder bridging, and insufficient solder.

 

  • Cold solder joints can lead to poor contact or even open circuits.
  • Solder bridging may cause short circuits.
  • Insufficient solder will weaken mechanical strength and electrical reliability.


If these problems occur in high-current devices or critical control modules, serious consequences will ensue. Therefore, to avoid these problems, multiple detection methods need to be adopted for quality control.

 

DIP soldering inspection



The AOI machine is used to quickly identify surface defects such as missed solders and solder bridging;

The X-Ray inspection machine is used to detect internal problems that are invisible to the naked eye, such as incomplete immersion of pins or voids in the solder joints;

 

In addition to machine inspections, manual inspection and sampling checks are still indispensable. Multiple detection methods are necessary to ensure the consistency and reliability of the solder joints without any flaws.

 

In terms of quality standards, DIP soldering needs to follow the IPC-A-610 standard. This standard sets clear requirements for the appearance of solder joints, the degree of wetting, and the control of residues. This standard regulates the manufacturing process of manufacturers and provides reliable quality assurance for customers.

 

Conclusion

 

DIP soldering is a traditional process and represents the durability and reliability of soldering in electronic manufacturing. Although SMT soldering technology has facilitated miniaturization and high-speed production, in areas that require mechanical strength, large current carrying capacity, and long-term stability, DIP soldering remains an indispensable solution.



About PCBasic



Time is money in your projects – and PCBasic gets it. PCBasic is a PCB assembly company that delivers fast, flawless results every time. Our comprehensive PCB assembly services include expert engineering support at every step, ensuring top quality in every board. As a leading PCB assembly manufacturer, we provide a one-stop solution that streamlines your supply chain. Partner with our advanced PCB prototype factory for quick turnarounds and superior results you can trust.


About Author

Emily Johnson

Charles possesses a deep professional background in PCBA manufacturing, testing, and optimization, excelling in fault analysis and reliability testing and proficient in complex circuit design and manufacturing processes. His technical articles on PCBA manufacturing and testing are widely cited within the industry, establishing him as a technical authority in circuit board manufacturing.

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