Printing the solder paste on the PCB (Printed Circuit Board) and go through reflow oven to re-melt the solder paste and solder the electronic components on PCB is most common process in today’s electronics manufacturing industry. Printing the solder paste on the PCB just like painting on the wall. The only different is solder paste printing ask more accurately position and must control the solder paste volume on each pad. It requires a certain jig call “stencil” is a sheet-metal made and have designate aperture on the position that needs to print solder paste.
Almost of current PCB assembly manufacturer apply the “stencil” jig to enhance the solder paste printing process to get more accurately printing position of solder paste and control the solder volume. Once the solder paste print shift from its pad too much then the solder will not joint the electronic component and PCB pad together. The solder paste volume over or less quantity will make solder short or open defect.
Recently one of my top manager ask to mount the shielding-can or call shielding-cover directly on the Printed Circuit Board to instead of mount the shielding-clip or call shielding-frame on the board first then cover the shieling-can. He said this “new process” is more cheap and can reach better RF (Radiation Frequency) performance. Also most of current popular cell phone board apply this solution.
First of all, with the rapid growth of mobile phone technology, the Electronic Manufacturing Service (EMS) in mainland China sometimes meet serious labor shortage. Second, the Industry 4.0 promotes the requirement of factory automation for each EMS. Therefore, many parts which cannot adopt SMT reflow process are requested to fulfill Paste-In-Hole process (PIH process), such as the type-A USB connectors, Ethernet connector, power supply sockets, transformers, and so on. Originally, most of these kind of devices were touch-up soldered after SMT process. 