For SMT processing, assembly and interconnection of printed circuit boards must adapt to the current rapid development of SMT chip assembly technology. And the use of SMT chip processing on PCBA circuit boards has been the mainstream of SMT chip manufacturers, nearly all circuit boards will use SMT chip processing, enough to see its importance in the circuit board. Today, GT professional technical staff to introduce you to the main features of SMT chip processing it.
1, high density: because the number of SMT chip processing pins up to hundreds or even thousands, the pin center distance up to 0.3mm, so the circuit board on the high progress of BGA need fine lines and fine pitch. Line width from 0.2 to 0.3mm reduced to 0.1mm or even 0.05mm, 2.54mm grid between the double line has developed to 4, 5 or even 6 wires. Fine line and fine pitch greatly improved the SMT assembly density. In the case of high precision of the corresponding SMT placement processing equipment, the corresponding placement processing plant can be completed.
2, small aperture: SMT in most metalized holes are not used to insert the component pins, in the metalized holes are no longer welding, metalized holes only as layers and layers of electrical interconnection, so to reduce the aperture as much as possible to provide more space for SMT placement. Hole diameter from the past 0.5mm to 0.2mm, 0.1mm or even 0.05mm.
3, low coefficient of thermal expansion: any material will expand when heated. Polymers are usually higher than inorganic materials. When the expansion stress exceeds the bearing limit of the material, the material will be damaged. As the SMT pins are many and short, the CTE between the device body and the SMT is not consistent, and damage to the device caused by thermal stress occurs from time to time. Therefore, the SMT circuit board substrate CTE should be as low as possible to adapt to match the device.
4, good performance in high temperature resistance: most SMT circuit boards today require the installation of components on both sides. Therefore, SMT chip processing circuit boards need to be able to withstand two reflow soldering temperature. Currently, lead-free soldering is widely used, the welding temperature is higher. After welding requires SMT chip circuit board deformation is small, no blistering, the pad still has good solderability, SMT chip circuit board surface still has a high degree of flatness.