라이브러리 제작시 PCB Hole size와 PAD 사이즈 계산하는 법

안녕하세요. 라이브러리를 제작할때 PCB홀 사이즈는 얼마가 적당할지? 고민이죠?

정확한 계산방법은 없습니다. 부품의 특성에 맞게 적당하 값을 선택해야합니다.

PCB의 홀(Hole) 사이즈는 리드핀의 굵기를 고려해서 결정합니다.

그렇다면 어떠한 이론적 근거를 생각해서 사이즈를 결정해야 할까요?

드릴 사이즈 대비 pad 사이즈는 얼마가 적당할까요?

PCB 라이브러리 만드는 룰을 IPC 문서를 활용하는 것이 좋습니다.

IPC-2222, IPC-7251, IPC-2221 문서에 내용이 있습니다.

1. Calculate the Minimum Hole Size

Minimum Hole Size is calculated according to equations below:

Minimum Hole Size = Maximum Lead Diameter + 0.25mm (for Level A of IPC-2222)
Minimum Hole Size = Maximum Lead Diameter + 0.20mm (for Level B of IPC-2222)
Minimum Hole Size = Maximum Lead Diameter + 0.15mm (for Level C of IPC-2222)

2. Calculate the Pad Diameter

After you calculate the Minimum Hole Size, you should know that the Minimum Annular Ring is
0.05mm (50um). According to IPC-2221 the Minimum Fabrication Allowance is 0.6mm for Level A, 0.5mm for Level B and 0.4mm for Level C.

Pad Diameter = Minimum Hole Size + Minimum Annular Ring X 2 + Minimum Fabrication Allowance

Pad Diameter = Minimum Hole Size + 0.1mm + 0.60mm (for Level A of IPC-2221)
Pad Diameter = Minimum Hole Size + 0.1mm + 0.50mm (for Level B of IPC-2221)
Pad Diameter = Minimum Hole Size + 0.1mm + 0.40mm (for Level C of IPC-2221)

Example: Maximum Lead Diameter = 0.55mm
According to Level A Minimum Hole Size = 0.80mm; Pad Diameter = 1.50mm
According to Level B Minimum Hole Size = 0.75mm; Pad Diameter = 1.35mm
According to Level C Minimum Hole Size = 0.70mm; Pad Diameter = 1.20mm

IPC-7251 Naming Convention for the Circular and Square Through Hole Pads

C + Pad Diameter + H + Hole Diameter (for the Circular Pad)
S + Pad Diameter + H + Hole Diameter (for the Square Pad)

Example: C150H90
C = Circular Pad
150 = 1.5mm Pad Diameter
H90 = 0.9mm Hole Diameter

Differences between density levels A, B and C

Levels A, B and C describe the measure of the relative ease of manufacturing.

Density Level A is used for General Design Producibility. It is a Preferred Level. Level A is used for the Low component density. In this case, footprint geometry is ‘Maximum’. This method is applied to the most robust producibility.

Density Level B is used for Moderate Design Producibility. It is a Standard Level. Level B conditions are suitable for reflow, wave, drag or dip soldering. In this case, footprint geometry is ‘Median’. This method provides a robust solder attachment conditions.

Density Level C is used for High Design Producibility. It is a Reduced Level. Level C is used for the High component density. In this case footprint geometry is ‘Minimum’. This method is applied to a hand-held and portable appliances.

#라이브러리 #홀사이즈 #PCB설계 #ARTWORK