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About Pad
Jun 10, 2018

Many people will draw a solder plate according to the component manual, but you should pay attention to how to draw the best solder plate. The following tips will help you learn more about the solder plate. 

Generally speaking, the welding disc can be divided into 6 categories, which are as follows according to the shape : 

1. Square welding disc -- when the components on the printing plate are large and small, and the printing wire is simple, it is usually adopted. When making PCB by hand, it is easy to use this kind of welding disc.

2. Island welding disc -- the connection between the welding disc and the welding disc is integrated. Often used in vertical irregular arrangement installation. For example, this kind of welding disc is often used in the recorder. 

3. Open-end welding disc -- it is often used to ensure that after wave soldering, the hole of manual resoldering disc is not sealed by soldering tin.

4. Teardrop welding disc -- it is often used when the wire connecting the welding disc is small, so as to prevent the peeling of the welding disc and the wire breaking off from the welding disc. This kind of pad is commonly used in high frequency circuits. 

5. Round welding disc -- widely used in single and double-sided printing plate with regular arrangement of components. If the density of the plate allows, the welding plate can be larger, so as not to fall off during welding.

6. Polygonal disc -- it is used to distinguish the disk with a similar external diameter and a different aperture, so as to facilitate processing and assembly. 

Oval welded disc - this type of disc has sufficient area to enhance the anti-stripping ability and is often used for double-row straight insert devices. 

▼ Design standard of shape and size of pad in PCB design(WELLS PCB&PCBA ODM&OEM)

1. The minimum unilateral diameter of all welding disks shall be no less than 0.25mm, and the maximum diameter of the entire welding disks shall be no more than 3 times of the element aperture. 

2. Try to ensure that the distance between the edges of the two pads is greater than 0.4mm. 

3. In the case of dense wiring, it is recommended to use oval and long round connection plates. The diameter or minimum width of the single-panel welding disc is 1.6mm. Double panel lines of weak current welding plate in a hole with 0.5 mm diameter, bonding pad too easy to cause unnecessary even welding, aperture is greater than 1.2 mm or welding plate is greater than 3.0 mm diameter welding plate shall be designed for the diamond or quincunx welding plate. 

4. The organic inserted parts shall be designed as drip welding plates along the bend foot direction to ensure full welding points at the bend foot. 

5. For plug-in components, in order to avoid the occurrence of copper foil breakage during welding, copper foil shall be completely covered on the single-side connection plate; And double panel minimum requirement should fill tear drop. 

6. The welding plate on a large area of copper shall be chrysanthemum-shaped, not soldering. If there is a large area of ground wire and power line area (more than 500 mm square) on the PCB, it should be partially open Windows or designed for mesh filling.


PCB manufacturing process requirements for pad

1. Test points should be added on both ends of the pasted element device without connection to the inserted element device, and the diameter of test points should be equal to or greater than 1.8mm, so as to facilitate online test of the tester. 

2. The size and spacing of the welding disc should be exactly the same as the size of the patch element.

3. If the IC foot welding plate with dense foot spacing is not connected to the hand plug-in welding plate, the test welding plate shall be added. If it is patch IC, the test point shall not be placed in the chip IC silk screen. The diameter of the test point is equal to or greater than 1.8mm, so as to facilitate the online test instrument. 

4. If there is a hand soldering element in a single panel, the tin groove should be removed. The direction is opposite to the direction of the tin passage. The width of the hole should be between 0.3mm and 1.0mm.

5. If the distance between the welding plates is less than 0.4mm, white oil shall be applied to reduce the continuous welding during the peak crossing. 

6. Tin primer shall be designed at both ends and ends of the patch element. The width of tin primer is recommended to adopt 0.5mm wire, and the length is generally 2 and 3mm. 

7. The spacing and size of the conductive rubber keys should be consistent with the actual size of the conductive rubber keys, and the PCB board connected with this shall be designed as gold fingers, and the corresponding gold-plated thickness shall be specified. 

8. The size and spacing of the welding disc should be exactly the same as the size of the patch element.

Wells Electronic Technology L.TD which  is one of the market leader in electronic industry in China  for PCB fabrication and PCB assembly with 10 years experience.