What are the most problems with smt footprint
As a member of the smt processing plant, based on experience, it is concluded that there are several packages and problems that are most prone to problems (according to the difficulty) as follows:
(1) QFN: The most common undesirable phenomenon is bridging, open welding (open welding).
(2) Tight-foot components: For example, SOP QFP below 0.65mm, the most prone to failure is bridging and soldering (open welding).
(3) Large-pitch, large-size BGA: The most common problem is the stress breakage of the solder joint.
(4) Small-pitch BGA: The most common undesirable phenomenon is bridging and soldering (open welding).
(5) Long fine-pitch surface mount connectors: The most common undesirable phenomenon is bridging, open soldering (open soldering).
(6) Micro switches and sockets: The most common problem is the internal rosin.
(7) Transformers, etc.: The most common problem is the open welding.
The main reasons for common problems are:
(1) The bridging of fine pitch components is mainly caused by poor solder paste printing.
(2) The cracking of solder joints of large-size BGA is mainly caused by moisture.
(3) Bridging and soldering of small-pitch BGAs are mainly caused by poor solder paste printing.
(4) The open welding of components such as transformers is mainly caused by the poor coplanarity of the components and pins.
(5) The bridging and open welding of the long fine pitch gauge connector is largely due to the PCB soldering deformation and the layout direction of the socket.
- The internal rosin of the micro switch and socket is mainly caused by the capillary action formed by the structural design of these components.
Above problems normally easy happened in production ,No matter the manufacturer ,but also the designer should be take care for it ,just to avoid any mistake or loss in production and design steps
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Thank you for the reading .