DfM Report PCB : 20-5001-00000030 RevP00 Client : Thomas&B etts1 1.In order to properly orient the TH connectors with respect to the wave and to avoid warpage of the board during wave soldering, the PCB must be oriented in the wave soldering machine with J5 or J12 in the front. This makes that most SMT components on the bottom side need to be rotated 90 degrees, just like C12 in order to be properly oriented, to avoid skips. 2.Still in order to prevent skip solder, the SMT component pads need to be extended 0.010” each towards the exterior, in order to allow for more wetting surface. 3.To avoid solder bridges on TH components, the annular rings of the TH parts have to be adjusted so that the Cu to Cu spacing is 0.035”, in the case of RoHS products. J5, J10 -13, J16 and all the JPs, at minimum, need the annular rings to be decreased. 4.Many SMT pads need thermal relieving connections to Cu planes, in order to avoid excessive heat during soldering and even higher heat, should rework be required. See red boxes in Image 1 for examples of the mentioned situation. For calculus of thermal reliefs see IPC- 2222 paragraph 9.1.2. They are defined in IPC-2221, paragraph 9.1.3. Image 1 5.Several polarized components, e.g. D5 and D7 have the polarity mark under the body of the component, once it is installed, therefore not visible after assembly, see Image 2. Polarity marks outside of the body is advisable.
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