Design dimensions of printed conductors and holes for pad

Shape and size of pad

The components are fixed on the printed circuit board by solder welding through the lead hole on the board. The copper box wire connects the pad  the electric connection of the device in the circuit.  The effect of the pad is when welding components, solder is placed to connect the pins of the components to the wire of the steel tube.

1) shape of pad

In the design of the pad, the shape of the pad is determined by the shape and size of the components, the vibration of the package form and the condition of heating and force.

Island pad, its solder and pad between the line into one, similar to the shape of a small island, so called island pad. Island pad is commonly used in vertical irregular arrangement installation.

With the use of island pad, the area of copper foil is increased, so that the printed wire of the pad is not easy to fall off, thus enhancing the anti-peeling strength of the product.

The round pad and the lead hole are concentric circles. The size of the pad is 3 times as large as the L diameter of the lead hole. Circular pads are often used in single-sided and double-sided printed boards with regular arrangement of components. In order to prevent the pad from falling, the pad should be as large as possible when the size of the board allows.

In the design of the circuit, considering that the distance between the two pins of the packaged integrated circuit is too short, and the lead passes between the pins, it is necessary to draw the round pad and change it into an elliptical long pad, Oval pad is a kind of pad which is widely used at present.

In a word, in the design of printed circuit, the shape of pad can be designed flexibly according to the actual situation. In the design, if the plate and wire are close to prevent short circuit. When the components are large, the precision is not high and the circuit allows, the welding pad can be made manually by etching.

In addition, in order to reduce interference, a large area of ground coverage is often used in design to prevent virtual welding or copper pipe warping, which affects the welding quality.It has two parameters: through hole diameter and pad diameter.

2) diameter of pad lead hole

The lead hole is in the center of the pad, its hole diameter should be slightly larger than the diameter of the welded lead wire, not too much small, in case it is difficult to insert components.

Lead hole

The pore size of Kong Tai cannot be too large, and the large size of Kong Tai can easily lead to defects such as virtual welding pores,

Make the mechanical strength of the connection worse.

3) size of pad

The size of the pad is determined by the size of the lead hole. Generally speaking, for a single-sided plate, the size of the pad is larger than that of the lead.

The diameter of the wire hole is larger than 1. 3mm; on the high density circuit board, the minimum diameter of the pad can be equal to the diameter of the lead hole

Add Imm; for double panels, the size of the pad is about twice the diameter of the lead hole.

2. Dimensions and shapes of printed conductors

The design of printed circuit board is mainly to design printed wire. The components on a printed circuit board are solid by printed wires current electrical connection. When designing printed conductors, it is necessary to determine the length and width of printed conductors, the dimensions of wire spacing, etc.

Size and graphic format can not be randomly selected, it relates to the printed circuit board size and circuit performance.

1) length and width of printed conductors

In general, printed conductors should be arranged as short and wide as possible to prevent parasitic inductors and parasitic capacitance pairs

The effect of the circuit is also conducive to withstand the current and easy to manufacture.

The thickness of copper foil is generally 0.02-0.05mm. Current intensity and allowable heating to determine relationship between thick printed conductors and their maximum operating current

In addition, the width of the printed wire is also similar to that of copper is related to the adhesion strength between the insulating substrates. The width of the conductor should be due to the size of the whole plate and pad should not be large group, should choose as wide wire as possible, the width of the wire like0. 3-2mm, of which 0. 5mm lead the width is mainly used for micro-miniaturization electronic products.

2) layout sequence of conductors

In the layout of printed wires, because the signal lines are more concentrated and the density is higher, it is necessary to consider the layout of signal lines first, however

Then consider the power cord and the ground wire. In layout, power lines and ground wires are much wider than signal lines and have less restriction on length

Some components use a large area of copper foil ground wire as a static shielding layer or radiator.

3. Design size of perforation

A hole is also known as a connecting hole. The conductive layers of the double panels and multilayers are insulated from each other, if different conductance is required the electrical connection between layers needs to be realized through a hole. The way to make a hole is to drill a hole in a multi-layer connection holes, and then deposit conductive metal on the wall of the hole.

The hole is used to connect the conductive pavilion between different layers, and its function is to connect with the copper wire, which is used to connect the elements.

Between pieces of pins. There are three types of perforations, namely, the channel holes and the semilaterial holes,.

Through the hole is a hole from the top to the bottom: from the top or bottom to a middle layer, instead of

The open hole is called the half blind hole, and the half blind hole is visible outside the board.

This is only used for conducting connections in the middle layer, not for the the hole that penetrates to the item layer.