Surface Mount vs Through-Hole: Pros & Cons
Surface Mount (SMT) and Through-Hole Technology (THT) are the two fundamental types of constituents utilized in printed circuit boards (PCBs). Surface Mount is used more frequently than Through Hole since it is more reliable and less expensive. Nevertheless, Through Hole Technology provides distinct advantages that ensure its continued relevance for the conceivable future.
Pros and Cons Side by Side
The following are some of the main pros and cons between Surface Mount and Through Hole Technology.
Pros
SMT is a space-saving alternative to Through Hole techniques, permitting tinier, lightweight, and speedier gadgets.
Surface Mount techniques permit cost savings that lead to lower unit prices.
Surface Mount technology achieves greater manufacturing capacity than Through Hole.
Assembly of SMT is automated due to process automations.
Through Hole Technology can easily withstand environmental stress.
THT creates stronger bonds between components.
Cons
Surface Mount Technology requires a higher level of design, production, skill, and technological innovation for implementation.
It isn’t easy to use SMT in visual inspection.
Through Hole Technology requires multiple holes on the board.
Through Hole has a longer production time compared to Surface-Mount.
Types of PCB Assemblers
You may employ a variety of methods for Printed Circuit Board assembling. Every method differs in its ability to handle board intricacies and execute particular construction and configuration techniques. The most basic types are:
Surface Mount Assembly: The procedure begins with loading the suitable constituents into the pick-and-place machine’s feeders, followed by programming the required functionalities.
Plated Through Hole Technology: The method is distinct in that it encompasses the use of holes that pass through the board. Most PCB assemblers use in-circuit testing.
Electro-Mechanical Assembly: The method uses various electromechanical equipment when building electronics onto PCBs.
What Is Surface Mount Technology (SMT)?
What is Surface Mount Technology? The SMT definition is that Surface Mount Technology is a technique for mounting electrical components directly onto the surface of a printed circuit board. Since gaining recognition in the 1980s, SMT has been prevalent in manufacturing nearly all electrical gadgets.
Enhanced Printed Circuit Board performance and reliability, as well as lower handling and processing costs, have made SMT an essential component of PCB design.
With SMT, you don’t need holes drilled in the board; instead, the constituents are soldered directly onto the board. SMT constituents are also tinier and fitted on both sides of the board. The capacity to accommodate more constituents on a PCB has permitted denser, more powerful, and more compact PCBs.
Advantages & Disadvantages of SMT
Constituents on SMT-fabricated PCBs perform well under shaking and vibrational conditions. The absence of holes in SMT translates to substantial cost reductions, minimal waste, and much quicker lead time. Quick constituent configuration (10 times faster than THM) results from a more dependable soldering method using reflow ovens.
Nevertheless, complications may arise when SMT is the only technique used to assemble PBC constituents subject to extreme mechanical, environmental, or thermal stress conditions. SMT constituents are also unsuitable for small circuit prototyping or testing. Combining the SMT and THM methods to obtain both advantages can resolve the issue.
What is Through Hole Technology (THT)?
Through Hole mounting is inserting component leads into drilled holes in a bare PCB. Before the emergence of SMT in the 1980s, through-hole technology was the industry-standard configuration method. The fact that Surface Mount is more efficient and less expensive has led many to believe that THT will become obsolete.
However, despite its drop in ratings over time, the Through Hole technique has been demonstrated to be resourceful in the age of SMT, providing numerous benefits and specialty implementations. Durability is the most notable advantage of through-hole technology, and currently, annular rings establish a durable connection.
Differences Between Axial and Radial Leads
Axial and radial leads are the two types of THT constituents. Axial lead constituents have wires attached to the component on both the front and the back. Radial constituents have the leads on one end side of the component.
Radial leads are preferable for densely packed boards because they take up less space than axial lead constituents, which fit snugly against the board.
Advantages & Disadvantages of THT
THT gives superior mechanical connections than SMT, rendering it ideal for mechanically stressed components like connectors and transformers. The expansive placement between the holes renders manual soldering of constituents easier. Additionally, THT constituents are easily interchangeable, making them ideal for prototypes and testing.
THT constituents are optimal for durable products requiring robust interlayer connections. THT connections permit constituents to endure more environmental pressures than SMT constituents, which are only held in place by solder on the board’s surface.
Consequently, the technology is prevalent in military and aerospace products subject to intense thrust, vibrations, or high heat environments.
When using Through Hole, you must drill holes in the bare PCB, which is both time-consuming and costly. THT also restricts the accessible configuration area on multi-layered boards, as the drilled holes must traverse all layers. Because THM’s constituent configuration levels are much lower than the surface mount, the technology is outrageously costly for most applications.
In addition, THT necessitates the use of wave, selective, or manual soldering methods, which are noticeably less efficient and dependable compared to SMT’s reflow ovens. Most notably, THT requires soldering on each side of the board, compared to SMT, which only compels soldering on one side.
Cost Difference
SMT, in contrast to THT, doesn’t require the manual drilling of holes in a PCB. A tiny PCB with minimal holes and layers will be less expensive. Additionally, pick-and-place cyborg systems expedite the configuration of components, whereas an automatic reflow oven handles reflow soldering. Thus, SMT has an additional benefit over THT regarding board cost reductions.
While manufacturers can expedite the configuration of THT for the easiest way to mass produce components, they opt for manual configuration due to component volume. Furthermore, THT configuration necessitates costly manual soldering to cover high-density components adequately. Since SMT offers higher automation agility than THT, board prices go down for bulk purchases.
Differences in Assembly
The main difference between Surface Mount and Through Hole assembly is that most SMT procedures are automated, which can significantly shorten assembly. You can anticipate your shipments to be processed faster with SMT manufacturing than with a THT procedure that requires configuring auto-insertion machinery for various THT mount constituents.
While SMT can shorten constituent configuration and board spin times, there are times when THT is the ideal alternative. For instance, the board design entails massive or robust constituents requiring extensive support.
Conclusion – What Is the Best Method for You?
Deciding on a suitable configuration method to bring your board to life can be challenging. Over 90% of today’s PCBs use surface mount technology, but which one is the best option for you? As a whole, surface mounting predominantly demonstrates more efficiency and affordability compared to through-hole technology. It gives a lightweight design and permits a high component density.
Nevertheless, unique mechanical, electrical, and temperature implications will continue to necessitate the need for THT mounting, ensuring its continued relevance well into the foreseeable future.
SMT Line: An Efficient and Cost-Effective Production Line in PCB Manufacturing
As electronics advance and components get smaller, they need cutting-edge equipment for accurate assembly. SMT lines are some of the most vital production lines in the PCB assembly process, and they contain several sophisticated machines for mounting devices on the surface. We have looked at the SMT line below, including the processes, types, and machines. Read on to learn more!
What is the SMT Line?
SMT is an abbreviation of the word Surface Mount Technology. On the other hand, the line refers to the production process used to mount electronic components directly onto a circuit board. It primarily consists of SMT machines, and these are the assembly line equipment needed to produce complete PCBs.
Why Do We Use SMT Lines?
We use SMT lines because they:
Safe
Using SMT production line equipment reduces the risk of injury because it makes the workers work less directly with the machine.
Save Costs
A complete SMT production line helps save on costs by:
Reducing the need for manual labor
Automated PCB manufacturing
Enhancing production efficiency and shortening the production cycle
Eliminating the need to store semi-finished components in the production process, which requires more space, hence more rent costs
Produce High-Quality Circuits
In addition to enhancing the production efficiency, SMT lines lower the defect rate because machines are more precise. The result is high-quality PCB production.
Improve Customer Satisfaction
Since the SMT production line improves quality and shortens the production cycle, it will lead to faster delivery of high-grade circuit boards. Such a production process will improve customer satisfaction.
Main SMT Line Fields
Semiconductor Industry
SMT and Semiconductor production is traditionally independent. However, integrating the two is a common practice nowadays due to the advancement in packaging technology.
Semiconductor packaging companies use SMT mounters to fit passive electronic components. Also, they employ semiconductor die bonders to connect die (chips), completing the SIP manufacturing.
There are several applications of the flip-chip or die bonder. Since chips are the main products of semiconductor manufacturing, there are different needs for chip accuracy.
Therefore, most chip manufacturers are acquiring (and merging) die bonder plants to streamline the SMT line.
LED Industry (Lighting)
LEDs are becoming the lighting standard due to their efficiency and durability. The LED industry also uses the SMT line to reap the benefits discussed earlier.
Automotive Electronics Industry
Cars are getting more intelligent because they use electronic systems to manage all their parts. Automotive manufacturing facilities began using SMT lines to fill in the demand required to mass-produce these modern cars.
Smart Industry for Home and Work
Combined with EMS, ERP, and MES systems, SMT lines can assist with order arrangement, production plan arrangement, material arrangement, etc. This combination can reduce production and warehousing costs by about 50% when dealing with products like:
Electric curtain control
Burglar alarms
Intelligent lighting
Gas leakage detectors and more
Electronic Consumer Goods (Appliances) Production Industry
SMT line also comes in handy when mass producing electronic consumer goods’ components. Think of TVs, sound systems, video game consoles, washing machines, etc.
Process of SMT Manufacturing
The process of SMT manufacturing includes the following steps.
Material Preparation and Examination
This step involves preparing the SMT components and PCBs while examining them for any flaws. At this stage, the PCB should be flat with solder pads (silver, tin-lead, or gold-plated copper pads with no holes).
Stencil Preparation
Stencils give fixed positions for solder paste printing. They should be in perfect alignment with solder pads on the PCB.
Solder Paste Printing
Solder paste is the material used to connect the SMT components to the solder pads. A solder paste printer applies it to the stencil above the PCB using a squeegee at a 45°-60° angle.
SMC Placement
The solder-printed PCB then heads to the pick & place machine, where the surface mount devices get placed on board. Some placement machines can position as many as 136,000 components per hour.
An automatic pick & place machine
Reflow soldering involves four steps. After going into the reflow soldering oven,
Step 1: The boards stay in the preheat zone where the SMD and PCB temperature gets elevated gradually. Reflow ovens ramp up the temperature by about 1-2°C each second until it gets to 140-160°C.
A reflow oven
Step 2: Boards then go into the soaking zone where the temperature remains at 140-160°C for about 90 seconds.
Step 3: Next, the PCBs head into the reflow zone. Here, temperatures rise about 1-2°C each second up to the peak of 210-230°C. Heat melts tin in the solder paste, bonding each SMD to the solder pads. The molten solder surface tension keeps the components in alignment with solder pads.
Step 4: Lastly, the PCB assembly heads to a cooling zone to freeze the weld and avoid welding defects.
The printing, placement, and reflow process can get redone using glue or solder paste to hold the electronic components in place when dealing with double-sided PCBs.
Cleaning and Inspection
The last step in SMT manufacturing is cleaning and inspection. The process involves automated optical inspection, x-ray machines, visual inspection, etc., then repairs follow if there are any defects.
Main SMT Line Machine
The PCB assembly equipment in the main SMT production lines includes the following:
Pick and Place Machine
This machine places surface mount components accurately on the PCB by moving the placement head to the right spot. The surface tension of the molten solder pulls the SMD into alignment automatically later on in the reflow soldering process to correct minor errors in component placement.
Solder Paste Mixer
A solder paste mixer mixes the solder paste and powder evenly and efficiently. It helps perfect the printing and reflow processes, standardize operations, and reduce manual labor requirements.
Oven
Ovens are different from reflow machines. They bake the circuit boards to eliminate any moisture and are usually last in the SMT line.
SMT Loader
This machine places PCBs into solder printing machine racks automatically.
Solder Paste Printing Machine
A solder paste printing machine prints the solder paste to empty circuit boards. It is usually ahead of the pick & place machine in the SMT line.
Solder Paste Inspection (SPI) Machine
SPI machines check the solder paste's area, thickness, and volume distribution on the circuit board after solder paste printing.
Reflow Machine
A reflow machine sits after the pick & place machine. It melts the solder between the PCB and SMT components to weld them, then cools the material to solidify the bond.
AOI
AOI machines sit before and after the reflow machines. They detect component placement failures before soldering (pre-solder inspection) and check for soldering failures (post-solder inspection).
Docking Station
Docking stations are intermediary stops between different machines in the SMT line.
SMT Unloader
An SMT unloader does the opposite of an SMT loader. It receives and stores the assembled circuit boards after reflow soldering.
An assembled PCB with SMD components
Types of SMT Production Line Layout
SMT production line layout types include the following:
One line a single-rail pick and place machine layout
Two-to-one line a single-rail or dual-rail pick and place machine layout
Two-to-one dual-rail pick and place machine high-speed layout
Three-to-one line a single-rail pick and place machine layout
Multiple line combination layout
SMT Line Development Trends
SMT lines have the following development trends.
CIMS Application
Computer Integrated Manufacturing Systems link the design and production processes to reduce the time taken for SMT production preparation.
Efficiency Improvement
Efficiency leads to higher output, and SMT lines are increasingly eliminating the human element. Another strategy is implementing centralized online management control systems for the entire SMT line.
SMT production line
Environmental Protection
Packaging materials, flux, solder paste, glue, and other items used in the SMT process can cause environmental pollution. However, PCB manufacturers and assemblers are increasingly adopting eco-friendly methods in this process. They analyze the pollution sources and the degree to which they appear in the assembly process, then minimize their impact on the environment as much as possible.
Flexible Information Integration Production Environment
Grid information technology and internet development provide process information control and product data management for improving SMT production lines. Also, they enhance maintenance management and will eventually create a flexible information integration production environment for SMT lines.
Summary
In conclusion, SMT lines are critical in the PCB assembly process, and they include several machines for different functions. We hope that this article has been insightful, and if you have any questions or comments, don't hesitate to reach out.
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