Almost every electronic circuit is composed of IC (integrated circuit) and ICs have become an essential element in advanced electronics. The design and development of ICs have rigorously evolved over the years; ICs have become compact, less power consuming, and more functional. But this change came with evolution in IC packaging; the IC packaging has evolved with time. Today, designers can choose between packaging types as per project feasibility.
But how do IC packaging types impact the efficiency of electronic circuit boards? The answer remains with the characteristics of IC packaging. Each package has different characteristics that in one way or the other make the circuit more effective. But before proceeding to the technical details; how IC packages differ, let’s first understand the basics.
What is IC Packaging?
Integrated circuits are developed with semi-conductors which are small and delicate. Given the small size of semi-conductors, a physical connection between the semiconductor chips and the circuit is challenging and impractical. Moreover, the chips have to be protected against corrosion and any unwanted electrical contact.
To protect chips and develop IC pins so that the semiconductor can be connected with the circuit, they are housed inside a package. The package can be smaller than your nails or it can be larger; depending on the package type.
The evolution in IC packaging started in the 1970s and since then, the IC packages have evolved to an extent that today, a Micro SD memory card holds much more data than a huge hard disk drive did in the 20th century.
Types of IC Packaging
Primarily, there are only two types of IC packages: Through-hole and SMD (surface mount device) but there are multiple sub-types.
Traditionally, through-hole devices are commonly used. They have legs extended enough to go through holes in PCB (printed circuit board). The devices are placed on one side of the PCB and soldered on the other side.
Since through-hole components are simple, they are less costly as compared to surface mount devices. This is why most of the low-cost electronics use through-hole components. However, through-hole components are several times larger than surface-mount devices which means they require more space on board.
Some of the common types of through-hole packages are as follows.
DIP (Dual In-line Package)
The name of DIP comes from its architecture; the pins are arranged in a dual/parallel order. DIP is also known as DIL and DIPP.
The number of pins is usually in a multiple of four, the housing is typically rectangular. However, the shape can be different for some devices; depending on the internal architecture.
The pins extended from the insides to a right angle towards the bottom. The distance between all adjacent pins is 0.1”.
DIP has further sub-types but the most common types are MDIP (molded dual in-line package) and PDIP (plastic dual in-line package).
Standard Through-hole Package
Standard through-hole package is the most commonly used type of through-hole package in industrial manufacturing. The standard through-hole package maintains a 0.1” distance between adjacent pins but there is no specific order of pins like in DIP.
Shrink package components are also the same as standard through-hole components except, shrink components are smaller and they have a 0.07” distance between pins. Shrink packaging is usually used for components that have several pins and have to be developed in a smaller size.
ZIP components also have pins extended outside, towards the bottom but they are a bit turned near the top. ZIP components did not gain popularity due to their bent architecture which caused complications during assembling process.
However, in the early years of its development, ZIP components were preferred in DRAM (dynamic random access memory) development. But today, ZIP components are rarely or no longer developed due to no demand.
SMT (Surface Mount Technology)
Surface Mount Technology is the second most commonly used technology of IC packaging for commercial-scale manufacturing. The components developed with SMT are called SMD (surface mount devices).
SMDs are compact and expensive as compared to through-hole packaging. But their compact size also enables the development of huge circuits on small printed circuit boards. Moreover, they do not require hole-drilling for pin soldering; all pins and the packaging lie on the same side of the board.
The components are picked, placed, and assembled on the PCB using special equipment. The fabrication process is less time-consuming but given the small size of SMDs, fabrication can be challenging. When multiple SMDs are placed closer, problems can arise and their detection is also difficult.
Two ease SMD assembling and fault detection, L-shaped Lead Package and Ball Grid Array are used. Both types are commonly used on an industrial scale.
L-shaped Lead Package
As the name suggests, the leads/pins of these SMDs are L-shaped. They extend out of the component housing, go vertically downward, and then take a right angle; getting parallel to the board which makes an L-shape. This L-shape keeps the leads in a horizontal direction to the boards which eases the assembling process.
L-shaped Lead Packages are commonly used in random access memory and power flash memory development.
BGA (Ball Grid Array)
BGA packaging carries an SMD chip but differently; the pins are not the only part that comes in contact with the bottom, instead the whole bottom of BGA sits on the board. The bottom is composed of small leads that form contact with the circuit.
BGA packaging is commonly used in high-speed applications especially computers. They can be seen on motherboards in computers.
Like in other types of packages, the BGA housing also slightly varies from IC to IC but typically plastic housing is used for enclosing the SMD chip.
Arduino Nano Board Developed With SMDs
IC Packaging Material
Just the way IC development is a technical process, the IC package development is also an extensively technical process. The material of IC packaging determines its characteristics which impact the circuit efficiency. Some of the commonly used IC packaging materials are as follows.
Materials Used in IC Packaging
Typically, certain types of materials are used in IC packaging. For example, glass and ceramics are used as insulators. Similarly, metals and polymers are used as conductors. Whereas the composites are used for thermal enhancement and conduction.
The Patch materials are fabrics, used for covering an unwanted opening in the IC packaging. Typically, the piezoelectric material is used in IC packaging as patch material. However, there are several other patch materials used in IC packaging.
IC Packaging Sealant
As the name suggests, the sealant is an adhesive/bond that seals the entire packaging. It works just like any adhesive/bond seals anything you want to seal and protect against water or moisture. The agenda of using a sealant in IC packaging is no different; it is to protect the semiconductor chip against moisture and water.
Since the semiconductor chip is delicate and can easily rust, the sealant helps protect it against rust. Moreover, the sealant keeps the packaging insides air-tight. Typically silicone sealants are used in IC packaging as they are highly durable and reliable. However, other types of sealants are also used in IC packaging.
Through-hole Devices VS Surface Mount Devices, Major Differences
As stated above, there are a number of differences in physical appearance and the way both packages form contact with the circuit. But apart from these differences, certain other factors must be considered when choosing one. The in-depth details of these factors are explained as follows.
As already explained, SMDs are quite smaller as compared to through-hole components. Their miniature size extensively reduces the space required for assembling which reduces the overall board size. For projects that have size limitations, surface mount device packaging is more feasible.
Surface mount packaging is much smaller than the through-hole packaging which is why the surface mount packaging can fit it in several components and yet remain smaller than the through-hole package. Apparently, surface mount packaging enables functionality achievement with lesser space consumption.
Despite extensive care and measurements, electronic circuit development is prone to errors. Whether it be a surface mount packaging-based circuit or a through-hole packaging-based circuit, fault can occur in both. But the difference comes in error detection and correction.
The miniature size of surface-mount packaging causes difficulty in error detection as all the components are extremely small and the pins are too close. Whereas in through-hole packaging, the overall size of the packaging is comparatively larger and the distance between pins is greater. This larger distance between the pins enables easy error detection as each pin can be approached easily.
Ability to Withstand Electromagnetic Signals
Electromagnetic signals can enter ICs and affect their functioning. It is essential to consider the electromagnetic compatibility of an IC packaging to ensure it is feasible for the desired circuit.
Surface mount packaging has better electromagnetic compatibility as compared to through-hole packaging. It means that the surface mount components are less prone to electromagnetic signals hence they are more efficient. This is because the surface mount devices have a shorter return path.
As already explained through-hole packaging is comparatively less-costly which helps reduce the overall product cost. Apart from that, there are other cost-savings associated with the use of through-hole packaging. For example, the assembling of through-hole components does not require any expensive equipment like a pick-and-place machine.
SMD and Through-hole Packages of NE555 Timer IC
How to Choose a Suitable Type of IC Packaging?
As explained above, there are several differences between through-hole and surface mount packaging and the designer has to consider multiple parameters. Apparently, choosing the right type of IC packaging can help save cost but a wrongly chosen type can cause certain compatibility issues and elevate product cost.
The role of IC packaging cannot be neglected when it comes to the IC’s effectiveness. The packaging keeps the IC safe and secure, protects it against mechanical stress and corrosion. Altogether these factors endorse the role of IC packaging in enhancing the circuit’s reliability. This is why designers must choose a suitable type of IC packaging before buying components.
Following are detailed factors that designers must consider while choosing IC packaging.
- The number of pins(inputs and outputs) must be considered. Typically, BGAs have a high number of pins whereas QFN (quad-flat no-leads) packaging components have a fewer number of pins. In case of limitations, the QFN package is more suitable but if you prefer a high pin count then the BGA package is more feasible.
- The thermal specificationsof an IC vary from package to package. It is not essential if the circuit has to operate at a nominal temperature and is not prone to excessive heating or cooling. But in the case of circuits that are prone to extreme atmospheric conditions, packaging’s heat management must be considered. Moreover, smaller components are likely to damage while soldering as their temperature elevates. So, the IC packaging must be chosen as per the thermal specifications. It is recommended to use BGA packaging for high heat-dissipation.
- Another important factor is the operational speedof the circuit. While choosing suitable IC packaging, always consider the high-speed I/Os. Again, for high-speed circuits, it is recommended to use BGA packaging.
- Lastly, consider the time needed to assemble the circuit. In some projects, the deadlines are short or several circuits have to be developed in a short time. Given the short time through-hole packaging takes to assemble, through-hole components are more suitable.
IC Packaging Selection; Key Take-aways
The role of IC Packaging in-circuit functioning is far more than just IC housing; it affects the efficiency of the entire circuit. Without proper IC packaging, the IC is prone to environmental effects, electromagnetic signals, and mechanical stress. Moreover, IC packaging has an important role in the assembling process.
Some IC packagings are more convenient to assemble while some are comparatively complicated. But all packaging types have pros and cons. The designer must consider the characteristics of IC packaging and circuit specifications before choosing an IC packaging.
When it comes to compactness and electromagnetic signal resistance, SMDs are suitable. But through-hole compoents are more suitable if the overall cost has to be kept minimum and the assembling process needs to be simple and less time-consuming.