SMT patch processing is the core technology in the SMT process, and the speed of patch processing often restricts the production line’s capacity.
An SMT chip processing production line must have at least one high-speed chip placement machine for mounting conventional size components and a multi-function chip placement machine for mounting special size components. Various problems are always encountered in the process of SMT patch processing. The editor of Zhongke Circuit Board Factory will introduce to you the causes and solutions of these common problems.
1. Poor wetting during PCBA processing
Phenomenon: During the soldering process, there is no reaction between the substrate solder area and the metal after the solder is infiltrated, resulting in less soldering or missing soldering.
(1) During wave soldering, there is gas on the surface of the substrate, causing poor wetting.
(2) When the residual metal in the solder exceeds 0.005%, the flux activity will decrease and poor wetting will occur.
(3) The surface of the welding area is contaminated, the surface of the welding area is stained with flux, or the surface of the chip component has generated metal compounds. Both situations mentioned above will cause poor wetting. Such as sulfide on the surface of silver and oxide on the surface of tin will cause poor wetting.
(1) Strictly follow the steps and instructions when welding;
(2) The surface of PCB circuit boards and components should be cleaned;
(3) Choose suitable solder, and set reasonable soldering temperature and time.
Phenomenon: One end of the component does not touch the pad and stands upright or it touches the pad but is still upright.
(1) It is related to the wettability of solder paste;
(2) The shape of electronic components is easy to produce tombstones;
(3) The temperature rises too fast during reflow soldering, and the heating direction is uneven;
(4) The wrong solder paste is selected, there is no preheating before soldering, and the size of the soldering area was selected incorrectly.
Solutions for PCBA processing:
1. Set the printing thickness of solder reasonably;
2. Reasonably formulate the temperature rise of the reflow soldering zone;
3. Store and retrieve electronic components as required;
4. Reduce the surface tension of the component ends when the solder melts;
5. The PCB circuit board needs to be preheated to ensure uniform heating during soldering.
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