What are the Applications of Solder Paste Dispensing Process in the SMT Industry?
In general, solder paste dispensing is a selective, non-contact solder paste coating technology that complements and expands traditional stencil printing. Although stencil printing is the mainstream, dispensing offers irreplaceable advantages in many specific scenarios.
Its main applications can be categorized into the following areas:
Ι. Primary Application Areas
1.Hybrid Technology Assembly
This is the most classic and common application for dispensing. It is used when a single PCB contains both Surface Mount Devices (SMDs) and Through-Hole Components (THDs), which traditionally require wave soldering.
Problem: During wave soldering, the already reflow-soldered SMD components (especially bottom-side ones) can be dislodged or damaged by the high-temperature solder wave.
Solution: Use the dispensing process to precisely deposit solder paste onto the pads for the through-hole components. Then, all components (SMDs and THDs) are placed and the entire board passes through the reflow oven once for soldering. This eliminates the wave soldering step, simplifies the process, and improves reliability.
Automatic In-line PCB Glue Dispensing Machine SEC-DH400L
Second Intelligent In-line Automated Glue Dispensing Machine SEC-DH400L adopts an integrated mineral casting design, with ultra-high precision and super stability, powerful expansion capabilities, and can realize ion cleaning, dispensing, detection, UV exposure and other functions;
Adopting a gantry structure, it can bear large loads, stable structure, and a powerful CCD visual positioning system, which can meet the requirements of Mark point positioning, edge positioning, and 3D scanning positioning; strong scalability, and can expand AOI detection 3D detection, UV exposure curing and other functions;
Strong platform compatibility, contact and non-contact dispensing, single-head and multi-head synchronous dispensing, automatic compensation and adjustment of double-head spacing, five-axis dispensing function based on needle A/R displacement, etc.
2.Bottom-Terminal Components (BTC) and Components with Non-Visible Pads
The solder joints of some components are located underneath the component body and are not visible, such as:
● QFN (Quad Flat No-leads Package)
● DFN (Dual Flat No-leads Package)
● BGA (Ball Grid Array) (Typically printed, but dispensing can be used in special cases)
● LGA (Land Grid Array)
For these components, traditional stencil aperture design is challenging and can lead to insufficient solder or short circuits. A dispenser can be programmed to precisely control the amount and position of solder paste on each pad, ensuring soldering reliability.
3.Stacked Assemblies or 3D PCB Structures
When the PCB surface is not flat and has significant height variations, stencil printing is impossible because the stencil must make complete contact with the PCB surface. Dispensing is the only option since it is non-contact; the nozzle can move relative to the PCB height, always maintaining the optimal dispensing distance.
4.Low-Volume, High-Mix Production and R&D Prototyping
● Saves Cost and Time: Producing a stencil has associated costs and lead times. For R&D prototypes, small-batch pilot runs, or production lines with a wide variety of products, creating a stencil for each product is not economical.
● Quick Changeover: Dispensing programs can be switched rapidly via software. A single dispenser can adapt to countless product designs, significantly increasing production flexibility and reducing setup time.
5.High-Density Interconnect (HDI) and Dispensing in Confined Spaces
In cases where PCB space is extremely limited and component pitch is very small (“fine-pitch”), stencil apertures can become fragile and prone to damage, or it may be difficult to guarantee print accuracy. Dispensing technology (especially jet dispensing) can achieve very small dot diameters (down to 0.2mm and below), precisely depositing solder paste in tiny gaps to avoid bridging.
6.Temporary Component Attachment
During assembly, some components (like connectors, large capacitors) may need temporary fixing before entering the reflow oven to prevent movement on the conveyor. A dispenser can apply a small amount of solder paste, using its tackiness to secure the part. This paste will then melt during reflow, forming the permanent solder joint.
7.Overcoming Thickness Issues Where Step-Stencils Are Not Viable
When a PCB side requires soldering both small components (like chip resistors) and high-power components (like large MOSFETs), the latter need a greater solder paste volume. The usual solution is a step-stencil (locally increased thickness), but this adds manufacturing cost and complexity. The dispensing process can easily apply multiple dots or larger dots of paste on pads requiring more solder without affecting the pads of surrounding small components, enabling flexible solder volume control.
Ⅱ.Advantages and Limitations of Solder Paste Dispensing
Advantages:
High Flexibility: No stencil required, suitable for various complex PCB layouts and small-batch production.
High Precision: Suitable for fine-pitch components and high-density interconnects.
Wide Applicability: Capable of handling complex scenarios such as uneven surfaces and mixed-technology assembly.
Reduced Material Waste: On-demand dispensing reduces solder paste waste.
High Integration: Easy integration with SMT production lines for automation.
Use 30cc glue barrel to dispense solder paste
Limitations:
Slow Speed: Compared to one-shot stencil printing, dispensing is a sequential process with lower production efficiency, making it unsuitable for high-volume production of single products.
High Equipment Cost: High-precision dispensing equipment (especially jet dispensers) carries a high investment cost.
Complex Process Parameters: Parameters such as dispensing pressure, time, temperature, and nozzle size require precise optimization, placing high demands on process engineers.
Potential Defects: Defects such as stringing, voids, and uneven solder content may occur, requiring strict control.
SMT automatic glue dispenser SEC-DH600L
Second Intelligent high precision smt automatic glue dispenser machine apply epoxy resin to the bottom of the PCB board for underfill
Second Intelligent smt automatic glue dispenser automation SEC-DH600L has the following advantages:
- CCD visual programming precise positioning, visual correction, improve programming efficiency and dispensing accuracy;
- Chinese and English operating system, the software interface layout is clear, the operation is simple, easy to learn and understand;
- Support visual inspection, integrated control of dispensing and visual inspection, multi-purpose machine, effective control of dispensing yield;
- It can be equipped with a lin e laser scanner for 3D path guidance and flexible dispensing;
- The software can support a variety of dispensing systems and functional module applications, such as automatic needle alignment, automatic
height measurement, dispensing weighing compensation, five-axis linkage and other functions, which can effectively overcome the difficulties of
various dispensing processes and help improve quality;
Summary: Solder paste dispensing is not intended to replace traditional stencil printing, but rather to serve as a powerful complement. It plays a vital role in specific applications such as hybrid technology, 3D structures, fine-pitch, high-density production, and small-batch, diversified production. As electronic products become smaller and more complex, and market demand shifts toward a wider variety of products with faster iterations, solder paste dispensing will become increasingly important in the SMT industry.
Second Intelligent has played an important role in theresearch, development, manufacturing, pre-sales and after-sales services of fluid dispensing robot, potting and coating solutions which range from various types of automatic fluid dispensing, potting, two-component potting machines and automatic coating machines with desktop, free-standing, inline or cobot combined systems, and widely used in global electrical, electronics, home appliances, automobile, telecom, pharmaceutical, automotive electronics, semiconductor, aerospace, LED and more.
