Main points of implementation of through-hole reflow soldering in PCB prototype patch factory

PCB model patch factoryThe through-hole reflow soldering process requires relatively high component temperature resistance. For leaded soldering, components should be made of resins that do not degrade within 60 to 90 seconds at 183°C and a peak temperature of 240°C. During lead-free soldering, components should be manufactured with resins that are above 220°C, with a peak temperature of 260°C, and do not deteriorate within 60 to 90 seconds. Let's take a look at the key points of implementation of PCB prototype chip manufacturers.

One is the pad design. In the PCB sample board placement factory, the through-hole pads of the through-hole reflow soldering process are generally designed to be round or oval. For manual insertion devices, the component pin diameter is generally 0.15mm-0.25m smaller than the diameter of the insertion hole; for the mountable interposer device, the component pin diameter is generally 0.3mm-smaller than the diameter of the insertion hole. 0.5mm; If the gap is too large, it is easy to cause false soldering, and the positioning accuracy of the device will also be reduced; if the gap is too small, the solder in the through hole is easily ejected by the component pins, resulting in empty soldering and solder balls. In addition, in the PCB sample placement factory, the distance between the through-hole pad and the surface mount pad should be greater than 0.5mm to meet the requirements of the stencil opening.

The second is steel mesh design. The key to reflow soldering of plug-in components in PCB prototype placement factories lies in the reasonable solder paste printing stencil design. Not only must the solder volume of the SMD component pins be carefully considered, but also the through-hole solder filling volume must be carefully calculated. Moreover, in the SMT process, the demand for solder paste between the surface mount pad and the insertion hole is very different, and the distance between the SMD component and the insertion pin is generally relatively small. In order to meet the demand for both solder paste, PCB The sample patch factory will take the following two relatively common measures: 1. Appropriately expand the stencil opening according to the through-hole pad ratio, and perform secondary printing at the position of the through hole; 2. Make a stepped stencil, and partially perform the stencil No matter what method is used for thickening or thinning, it needs to meet the basic requirements of stencil opening area ratio ≥ 0.71 and width to thickness ratio ≥ 1.6. At present, the through-hole reflow soldering process of PCB sample board placement factories generally uses stepped steel mesh to increase the amount of solder paste in the through-holes.