ECE210 - Lab 4 - Soldering and Thevenin

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School

University of Massachusetts, Amherst *

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210

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Electrical Engineering

Date

Jan 9, 2024

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pdf

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Uploaded by DoctorPorpoiseMaster992

UMass ECE 210 – Fall 2023 Lab 4 : Soldering and Thevenin Equivalents GOALS: • Solder through-hole components into a printed circuit board (PCB) • Thevenin equivalent circuit analysis DATA required for Lab report (get instructor check off before leaving): TABLE - Thevenin equivalent voltage and resistance PICTURE – Soldered circuit with closeups of joints SPICE SIMULATION – Diagram and DATA Introduction: Soldering through-hole components into a PCB Soldering is an essential skill for electrical engineers. You will solder through-hole components (resistors and header pins) into a printed circuit board (PCB) with a soldering iron and then measure various voltages and currents in the circuit. You will verify Thevenin’s theorem by measuring the equivalent voltage and resistance of your circuit and compare them to your theoretical calculations.

PART 1 – SOLDERING SAFETY: 1. Always wear safety glasses! (Solder can splatter into your eyes easily!) 2. The iron will heat any metal it touches hot enough to burn you. Be careful! General Soldering Tips: 1. Keep your workstation neat and organized 2. Solder will STICK to the tip of the iron if it is clean and ready for soldering (Clean with tip tinner for 10 seconds if solder does not stick) 3. Check resistor values with Multimeter BEFORE soldering 4. Watch: Basic Soldering Lesson 6 - "Component Soldering" 5. Watch: SDG #066 Solder Through-hole Components - Soldering Techniques #02 Solder Station Setup: 1. Plug in your iron fully and turn on your soldering station 2. Set the temperature to 750° F (we’ll be using lead-free solder) 3. Increase the standby time so it stays on longer than a few minutes. 4. Wet the sponge and turn the cuts in the sponge front/back (If the cuts are sideways, the sponge will FLING MOLTEN solder) 5. Clean your safety glasses with alcohol spray at the front of lab (WEAR THEM!)

Solder the header pins into the PCB for applying voltage to the circuit: 1. Break pins into single pins, then insert them in the board for V1 and GND. Cut with a snips and be careful as the pins can go flying if not held. (Another reason to wear your safety glasses!) 2. To hold the pins in place while you solder them, use a breadboard (or black sponge) to hold the header pins while they’re inserted into the PCB, with the PCB upside down . Otherwise, the pin could slide down and make it hard to connect to. 3. Apply the solder iron tip to the PCB pad and to the component lead (wire) simultaneously to heat them up before adding any solder. It should heat up in just a few seconds if your solder iron tip is already ‘tinned’ with a little solder. 4. Once the PCB and component lead are hot, apply a small amount of solder to the PCB pad and the component lead. You should not need to touch the solder directly to the iron tip. The solder should melt just by touching the PCB pad and flow freely, ‘wetting’ the surface of the PCB and creating a concave meniscus with good adhesion. Take turns with your lab partner soldering components. Keep your iron tip clean as you solder by brushing it off with the brass sponge or sponge with water to remove excess flux. Excess flux will burn on to your tip and prevent it from tinning properly. Brass cleans the tip without damaging it. Any burnt areas on the solder tip will not conduct heat and the solder will not melt. Tin your tip often! Turn off your solder iron when not in use! Keep your soldering station in good condition for the next group!

Inspect your joints and repair if you see: 1. Excess Solder or shorting between pads: Remove with a solder wick. Laying the wick on the solder and heating the wick will cause the solder to be drawn up the wick and remove it from the pad. You can use extra flux to help wick the solder up. (ASK a TA for assistance). 2. Not enough solder: Reheat joint and add a little more solder 3. Cold joint: Reheat the joint after re-tinning your iron tip 4. Too much heat: Ask TA for help. You may need a new board. 5. Shorting: Same solution as excess solder above. Use solder wick to remove solder.(Ask TA for help) If the joint is good place the jumper connector onto each exposed header pair on the board as you go and verify, they all make solid and firm connections. Test that the jumper fits tightly. It should NOT wiggle. Continue until all the header pins have been soldered. The smoke: You’ll notice your iron smokes when you melt new solder, but then stops. Why? The smoke stops because the FLUX inside the solder burns away, leaving just the metal. Without flux the solder doesn’t flow as well. You can add just flux with a flux pen, but it is often convenient to just add more solder (which has more flux inside).

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