What are Access Holes

The holes present on a PCB can be classified into three types, namely Plated Through Hole (PTH), Non-Plated Through Hole (NPTH), and Via Holes. It is important to note that these should not be mistaken for Slots or Cut-outs.

Vias are essentially plated holes that serve the purpose of connecting tracks on different layers, rather than being used for mounting through-hole components like regular holes. It is important to note that while holes can also be used to connect tracks on different layers, their primary function is for mounting through-hole components.

A via is a plated through hole (PTH) in a PCB that serves the purpose of providing electrical connectivity between different layers of the printed circuit board by connecting traces on different layers. It is not intended for mounting component leads, and therefore, it usually has a small hole and pad diameter.

The small openings on a PCB where solder is applied are commonly referred to as “solder holes” or “through-holes.” These holes can also be known as “pin holes” or “blow holes,” which are caused by the outgassing of the printed board during the soldering process. The formation of these holes during wave soldering is typically linked to the thickness of the copper plating.

Through-hole technology is a manufacturing process commonly used in electronics. It involves inserting component leads through drilled holes in a printed circuit board (PCB) and soldering them to pads on the opposite side. This can be done either manually or through automated insertion.

A blind hole and a through hole differ in terms of their depth. A through hole passes through the entire wall of a part, creating openings on both sides. On the other hand, a blind hole has a specific depth and does not break through to the other side of the workpiece.

Through-hole technology offers a significant advantage as it results in a more robust connection between the board and components. This makes it an ideal choice for larger components that are subjected to high power, high voltage, and mechanical stress, such as transformers, connectors, and semi-conductors.

The two primary types of through-hole components are axial lead and radial lead. Axial lead components have leads on both ends and exit the part in a straight line. On the other hand, radial lead components have both leads on one side.

Through-hole PCB components are preferred for high-reliability products that require stronger interconnections between layers. In contrast, SMT components are only secured by surface soldering, while through-hole component leads run through the board, making them more resistant to environmental stress.

In the process of drilling PCBs, various types of holes are created, such as component holes, mechanical holes, and via holes (including blind holes, buried holes, micro-holes, and thru-holes). To achieve the necessary accuracy, the holes are typically created by means of a manual or laser PCB drill.

Surface mount technology allows for higher manufacturing capacity compared to through hole technology. This is due to the automated assembly process involved in SMT. However, through hole technology is better equipped to handle environmental stress and creates stronger bonds between components.

There are two types of mounting holes in PCBs: supported and unsupported. Supported holes are plated and usually connected to the ground plane, while unsupported holes are non-plated and require an outer keep-out zone to prevent interference with other components and traces as they are not connected to a ground plane layer.

BGA (Ball Grid Array) soldering is a technique that involves the permanent mounting of integrated circuits using a grid of solder balls beneath the components. In contrast to SMT or through-hole techniques, where only the perimeter of the components is soldered, BGA utilizes the entire bottom surface area of the device for connections, resulting in a more comprehensive and efficient connection.

SMD and SMT are two terms that are often used interchangeably, but they actually refer to different things. SMD stands for surface mount device and refers to the electronic component itself that is mounted on a PCB. On the other hand, SMT stands for surface mount technology and refers to the process of placing electronic components on a printed circuit board. So, the main difference between SMD and SMT is that SMD is the component, while SMT is the process used to mount the component on the PCB.

Through-hole technology, also known as “thru-hole”, is a mounting method utilized for electronic components. This method involves inserting leads on the components into drilled holes on PCBs and soldering them to pads on the opposite side. The assembly process can be done manually (by hand placement) or through the use of automated machinery.

A clearance hole refers to a hole in an object that is large enough to allow the threads of a bolt or screw to pass through, but not the head of the bolt or screw. This type of hole is designed to prevent the threads from biting into the material and allows for easy insertion of the screw or bolt.

The term “hole” originated from the Old English word “hol” which means “cave”. In ancient times, caves were not only used as hiding places but also served as dwellings. The word “hole” is now used in various contexts such as a rabbit’s dwelling or the golf term “a hole in one”.

Examples of holes include the central “hole in a donut” shape found in a torus, a section removed from a plane, and the area that is absent from Euclidean space after a knot is removed from it.

The various hole patterns can be classified into four types: round, square, slot, and ornamental or decorative. Round holes are widely used due to their simplicity and cost-effectiveness.

One of the drawbacks of through-hole technology is that it requires pre-drilled PCBs, which can be costly and time-consuming. Additionally, THT components can only be placed on one side of the board, and on multilayer boards, the available routing area is limited due to the need to drill holes through all layers of the PCB.

Tooling holes, also referred to as Fabrication Hole, Pilot Hole, or Manufacturing Hole, serve the purpose of providing registration and hold-down points on a PCB or a panel of PCBs during the manufacturing process.

Benefits of Copper Filled Vias:

Copper filled vias are necessary because they enhance the thermal conductivity of the via. This is particularly important in applications where high heat is involved, as it helps to keep the heat away from the board, thereby increasing its lifespan and preventing defects.

The 2 layer PCB, also known as a double-sided PCB, consists of a printed circuit board with copper coating on both the top and bottom sides. The middle layer is an insulating material commonly used in printed circuit boards. This design allows for layout and soldering on both sides, making it easier to layout and reducing the difficulty of the process. As a result, it is widely used in various applications.

The distance between two holes in a PCB depends on the type of hole. For PTH, the minimum distance from the bonding pad to the hole to outline should be at least 20mil (D≥20mil). As for NPTH, it is recommended to have a minimum distance of 40mil from the hole to outline (E≥40mil).

4 layer through-hole PCB is a type of printed circuit board that is composed of four layers of glass fiber. The layers include the top layer, bottom layer, VCC, and GND, which are connected using through holes, buried holes, and blind holes. Compared to double-sided boards, 4 layer through-hole PCBs have a higher number of buried and blind holes.

Drilling plays a crucial role in the construction of PCBs, whether it’s a single-layer board that needs mounting holes or a multilayer PCB that requires vias. Typically, both types of drill holes are necessary, along with other variations.

The drill bits used in this drilling technology have a minimum diameter of approximately 6 mils (0.006″), which is the smallest hole size that can be drilled on a PCB.

For through holes, it is recommended to use a tap with a straight flute, which is suitable for both through and blind holes.

To achieve the best thread engagement, it is generally recommended to have a thread depth of 1 1/2 times the screw diameter. For instance, if the screw diameter is 1/4″, the thread depth required would be (1.5 x .25) = .375″.