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Clean and shiny solder (indicates good wetting and bonding)Wires are tightly twisted or overlappedEntire joint is fully coated with solder — no exposed copperThe shape is smooth, not lumpy or blobbyNo sharp points or spikes (can lead to shorts)Wires are overlapped about 1–2 cm (½–¾ inch) for good mechanical strengthSolder flows into and around the wire strands or overlapThe joint should look like one continuous piece, not two wires just stuck together
Cold Joint: Dull, grainy, or frosted appearanceInsufficient Solder: Wires are only partially coveredExcess Solder (Cold Blob): Huge blobs of solder sitting on top without wetting the wiresPoor Overlap or Contact: Wires are barely touching, or not twisted properly
Cut off part of the insulation of two wires Tin each wire (Coating wires in a thin layer of tin before connecting them)Solder the wires together
Identify the top of your PCB. Insert both leads of the resistor into the PCB. Bend the legs of the resistor slightly to hold it in place. Following the soldering tips from the Lab Joint section above, apply head to the resistor leg and soldering pad for about 1 second. Next feed a small amount of solder into/onto the heated solder pad/component leg. Hold the soldering iron in place until the solder flows. Using solder wick, remove the solder from the component and hole completely.
Lab 4: Soldering
This lab covers soldering. Soldering is the process of using a metal alloy with a low melting temperature to fuse together two other pieces of metal. This is used in all electronics for two reasons: 1. It ensures a strong mechanical connection (i.e. the wires in your computer don’t fall off the circuit board in transit) and 2. Provides a highly conductive electrical connection.
Tips for Good Solder
To make a good solder joint you need four things:
Clean leads on each component to be connected. Generally, in lab, component leads are sufficiently clean that no special action need be taken. However, when performing repair work, this will not be the case. More of repair soldering later.
A good mechanical connection. Solder is not that strong and is malleable, so you need a mechanical connection in addition to the solder (electrical) connection. Generally, unless the components are damaged, the components are designed with adequate mechanical strength.
Plenty of heat to warm the wires and melt the solder. Soldering involves heating the component leads/wires and circuit board pads to a sufficient temperature that the solder melts and flows around the mechanical connection.
Soldering is easier and a better connection is made with the soldering iron tip is clean and shiny. Soldering is easier because a clean tip transfers heat to the connection faster than a dirty tip. A better connection is made because there is less chance that crud gets into the connection.
Lap Joints
A lap joint is when two wires are connected by overlapping them and soldering them together (fig 1).
Fig 1: example of lap joing
What should a good lap joint look like...
What a lap joint should not look like
Steps to make a lap joint
Through Whole PCB Solder
Through hole PCB soldering is how you attach electric components to a PCB (Fig 2).
fig 2: example of PCB solder
Steps
My Solders
Lap Joint: During this lab I made 5 lap joints. I learned that it is very easy to apply to much solder (fig 3). I also learned that it is very easy to apply to much heat on the wires which can create hot spots (fig 4). I did have a really good lap joint however that I am very proud of (fig 5).
Fig 3: Example of to much solder
Fig 4: example of solder with hot spots
Fig 5: Good Solder
PCB: PCB Solder I found to be a little bit easier since it was a lot more stable than soldering 2 wires. The main thing to remeber here is that the solder creates a volcano. I made 2 PCB solders. One I didn’t get the proper volcano shape (fig 6) but the other one is good (fig 7)
Fig 6
Fig 7
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