Transcript Slide 1
Assembly Techniques Electronics Unit – Lecture 4 Component Preparation Component Placement and Soldering Inspection Activity – Assemble and test SkeeterSat LSU 06/04/2007 Electronics 4 1 Component Preparation Axial Lead Components Most will require their leads to be bent to conform to the spacing of the hole in the circuit board. Use a lead bender if possible. Otherwise, always grasp the lead, not the component body, when bending leads. LSU 06/04/2007 Electronics 4 2 Component Preparation Radial Lead Components A well-designed board will have the holes spaced to match radial lead parts. If adjustment must be made it must be done very carefully. LSU 06/04/2007 Electronics 4 3 Component Preparation Integrated Circuits When IC chips are to be soldered directly on to circuit boards (a socket is not used) their pins are often slightly too far apart and must be gently aligned. Be sure to be grounded when handling ESD sensitive chips. LSU 06/04/2007 Electronics 4 4 Component Placement Observe the proper orientation of polarized components. Note banded end of diodes, and notched end of IC chips Components should be as close to the board as possible without stressing the leads. Orient components so that their value markings can be easily read after installation. Have resistor color bands all reading in the same direction. LSU 06/04/2007 Electronics 4 5 Inspection Inspect Twice, Solder Once Be sure that the correctly valued component has been inserted into the correct location, with the proper orientation, BEFORE soldering any leads. After soldering one lead it’s good practice to inspect again before soldering the rest of the leads. LSU 06/04/2007 Electronics 4 6 Inspection After all leads are soldered, inspect again, looking for: “Dry” or “cold” solder joints Poor adhesion of solder to pads or leads Solder bridges across traces or pads Unsoldered leads 90 % of all failures are related to soldering problems LSU 06/04/2007 Electronics 4 7 In Case of Emergency… So, after all your best efforts and careful inspection, you made a mistake….. LSU 06/04/2007 Electronics 4 8 In Case of Emergency… So, after all your best efforts and careful inspection, you made a mistake….. Don’t Panic… Remain Calm… Components can be removed from a circuit board. LSU 06/04/2007 Electronics 4 9 In Case of Emergency… Use a “solder sucker” or “solder wick” to remove solder from the hole. It’s usually wiser to sacrifice the component by cutting it’s leads off, then removing the leads one at a time. This will avoid damaging the traces on the circuit board, which are very difficult to repair LSU 06/04/2007 Electronics 4 10 Activity E4 Assemble and test your SkeeterSat. LSU 06/04/2007 Electronics 4 11