Electronic gadgets run the world. We depend on them from toothbrushes, coffee machines, and robotic vacuum bots, to noise cancelling headphones, smartphone-powered lights, and cars with lane assist and backup cameras. 

There’s a tiny piece inside each of those life-improving gadgets that powers it. In the electronics field, that component is called a Printed Circuit Board (PCB). To everyone else, it’s called a chip.

Placing and fastening miniscule electronic components on the tiny (usually green) chip is a precise process called PCBA (printed circuit board assembly). What materials and techniques are used in PCBA to attach components to the board? Of the many options, what works best?

Let’s dive into that!

(SMT) Surface Mount Technology

Surface mount technology is a technique used for mass production. An automated pick-and-place machine picks up components (also called SMDs) and places them on the surface of a board, fastening them with solder.

SMD (Surface Mount Device)

SMD stands for Surface Mount Device, a type of electronic component mounted directly onto a circuit board using an SMT machine. Soldering paste fastens the components. SMDs take up less space than leads. These components make it easier to manufacture smaller, more compact PCBs.

BGA (Ball Grid Array) Soldering

A ball grid array (BGA) is a type of surface-mount packaging. BGAs are used for integrated circuits, specifically for SMDs like microprocessors which require permanent mounting. Though it is a type of SMT, the ball grid array uses a different approach to connections. This technique permanently mounts integrated circuits using a grid of solder balls under the components.

Unlike SMT or Through-hole techniques where only the perimeter of the components is soldered, with BGA, the entire bottom surface area of the device is used for connections. BGA boards have more interconnections than normal PCBs, allowing for high-density, smaller sized PCBs. Since the pins are on the underside of the board, the leads are also shorter, yielding better conductivity and faster performance of the device.

There are three types of BGAs, depending on the material used for the substrate.

The PBGA or Plastic BGA uses BT resin/glass laminate for the substrate, along with plastic packaging material. It is used in high-efficiency devices as they are low cost, and offer convenient surface mounting with a high reliability.

The Tape BGA (TBGA) package is good for medium- to high-end applications with heat dissipation but no external heatsink. They use two types of interconnections between the substrate and the board based on lead and inverted solder bonding.

The Ceramic BGA (CBGA), as the name suggests, uses ceramic as the substrate material.

PCBs with BGA components are smaller in size, cheaper, and are densely packed with connections on a small surface area. They deliver superior performance with high reliability, making them ideal for high-performance applications such as CPUs, data controllers, or mobile phone processor chips.

There are a few drawbacks to BGA assembly: The pins are densely packed on the board and each pin requires a precise amount of solder paste. This is better achieved by automatic machines rather than manual processes. Also, since the connections are on the underside of the board, optical inspection is not possible and so BGA PCBs require X-ray inspection. 

Through-hole Technology

Through-hole components are wired leads (legs) that are pushed through drilled holes on the circuit board. Traditional manual assembly used through-hole technology. However, wave soldering machines are now available in the market to secure through-hole leads at high volume. 

What Works Best in PCBA: SMT, BGA, or Through-hole?

For low-volume PCB production (such as prototyping), through-hole technology may work best. Through-hole is often regarded as the better choice for components that need to handle high stress—wire leads provide a strong bond. Through hole is often the choice mount technique for front connectors where USB cables and cords will be plugged in. However, there is an extra cost associated with drilling holes and soldering on both sides of the PCB is required, which adds time to production. Through hole connectors also limit the routing area on multi-layer boards.

Modern electronic devices demand multiple high-level functionalities, efficient performance, and increased speed—all in a reduced device size.  Even with an increased number of electronic components, the assembly must be thinner. BGA packages are ideally suited for these requirements. For example, ICs with more than 200 I/O terminals are usually manufactured using BGAs.

When production volumes are high, Surface Mount is a better choice because the SMD components take up less space making for a more compact, component-dense circuit board. Since SMDs are conducive to automation using pick-and-place robotic machines, SMT is a more reliable technique than hand-assembly using through-hole technology—no drilling required. SMT is the industry standard technique for back connectors. There are, however, a couple of disadvantages of SMT: it’s not ideal for attaching high-stress components and SMT requires an initial investment in expensive machinery for large-scale production.

Overall, SMT is more cost-effective and time-efficient.

Why the Shift to SMT?

Regardless of the pros of through-hole mounting mentioned above, surface mount technology offers many advantages that make it best for PCBA. 

SMT allows the placement of components on both sides of the board, allowing a much denser placement of SMDs on the board. Complex connections are possible in a limited space. SMT results in lighter and more powerful PCBs. A greater level of component density also reduces processing power during assembly. SMT does not require drill holes (which slows production and adds cost).

Surface Mount Technology works best in PCBA as the rate of assembly is as high as tens of thousands of placements per hour. On the other hand, through-hole technology assembles components at a speed of less than a thousand per hour. SMT solder joints are much easier to automate with repeatable tasks programmed into robotic machines. 

In a market where production delays can cause an organization to lose customers and their trust, being fast and reliable is crucial for business success. That’s why surface mount technology in the PCBA process wins the manufacturer’s favour.

Trust MIS Electronics to fulfill your PCB assembly specs, whether you are looking for hand-assembled through-hole technology for prototypes or high-volume SMT production. We have decades of experience delivering high-quality PCBA services as a proud Toronto-area manufacturer with a proven track record. Get a no-obligation quote from us today.