Mounting process of different packages for SMD components
The packaging structure of SMD is the basis of process design. It is classified according to the structure of pins or soldering terminals: mainly chip components (Chip), J-shaped pins, L-shaped pins, BGA, BTC, Castle class
Chip component packages mainly include chip resistors, chip capacitors and chip inductors. Packages with a size of 0603 and above have good manufacturability, and under normal process conditions, there are few soldering problems; packages with a size of 0402 and below have poor manufacturability, and are generally prone to adverse phenomena such as tombstoning and flipping.
J-lead pin packages include SOJ, PLCCR, and PLCC, which have better solder resistance. The J-lead pin type package has a large lead-lead spacing and is not easy to deform. Under the general process level, there will be no poor welding problems, and it has very good manufacturability.
L-shaped(Gull-wing lead) pin packages mainly include SOIC, BQFP, QFP, SQFP and QFPR, and TSSOP has better solder resistance. It is easy to absorb moisture, and it is necessary to confirm whether the moisture absorption exceeds the standard before use. If the moisture absorption exceeds the standard, it should be dried. Package pins with a pin pitch of 0.65mm or less are relatively thin and easily deformed, so be careful when handling them. Packages with a pin pitch of 0.40mm and below are very sensitive to the amount of solder paste. A little more may cause bridging, and a little less may cause open soldering.
The BGA pins (solder balls) of the BGA package are located under the package body, and the soldering situation cannot be directly observed by the naked eye, and X-ray equipment must be used for inspection. BGA is a moisture-sensitive device. If it absorbs moisture, it is prone to welding defects or defects such as "popcorn" and deformation. Therefore, it must be confirmed whether it meets the process requirements before assembly. BGA is also a stress-sensitive device. The stress of the four corner solder joints is concentrated, and it is easy to be broken under mechanical stress. Therefore, it should be placed as far away as possible from the edge of the panel and the mounting screws when designing the PCB.
BTC packages mainly include QFN, DFN, SON, LGA, and MLFP. The manufacturability of BTC packages is relatively poor. In other words, soldering is relatively difficult. Common problems are voids in the solder joints, virtual soldering or bridging of surrounding solder joints.
BQC has 19 years of production experience, and has rich placement experience for any packaged SMT components. It can timely and effectively avoid some risks of poor placement, and control the entire production process with high efficiency and high quality.
