Working Practices

 
These Techniques described later can only be SUCCESSFUL if the guidelines below are followed:
  • CAD Considerations
  • Lighting
  • Cleanliness
  • Hand Tools

 
CAD Considerations

The PCB Design will need modification at the CAD Level to enable these techniques to be WORKABLE:

  • VIA PADS need to be at least 55 to 60mil diameter IF the drilling is to be done BY HAND.

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  • SMT Rectangular Pads MUST be LONGER so that they protrude out and are VISIBLE even when the device is sitting on the pad. This is so that you can observe and create a reliable joint when manual soldering.

 
Lighting

Use 2 standard 60W DESK LAMPS one either side of your work area and placed low to the bench to give maximum intensity. This will illuminate the work area adequately and not produce SHADOW.

Visual Inspection is the KEY to success.

Most faults are VISIBLE with
the lighting described above.

With these techniques you have to rely TOTALLY on
YOUR OWN EYES for quality control.

THE MORE LIGHT YOU HAVE,
THE MORE YOU'LL SEE

 
Keeping Everything Clean

Before any soldering work is done on the pads they need to be cleaned with IPA (SEE BELOW) using a soft toothbrush style brush to remove oxides.

The PCB will re-oxidize within an hour, so
clean JUST BEFORE you intend to solder.

IPA (Isopropyl Alcohol) is used in AEROSOL SPRAYS as a diluent and solvent and is a common component of such products like MAGNETIC TAPE HEAD CLEANING SOLUTIONS. It has the advantage that it EVAPORATES quickly.

 
Hand Tools

Standard tools are adequate for the job, accept for the ones mentioned below:

  • Soldering Iron
    • Modern Temperature Controlled types are adequate. The Solder Tip needs to be pointed thus giving access to individual SMT joints.
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    • Pointed Tips when used on SMT Pads have an added advantage of less heat capacity. So once placed on an SMT pad the temperature drops rapidly. This has the advantage that quick joints can be made on the tiny pads without them getting damaged.
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  • Tweezers
    • DON'T use SHARP ones! These may DAMAGE delicate SMT resistors. Flat Ended types are preferable as rounded ones can't be used to pick up the smaller SMT devices.
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  • Solder Braid
    • Use the narrowest grade you can. Using fat ones take too long to heat up which may damage the pads.
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  • Inspection Eyeglass
    • These are available in different magnifications. A X8 magnification is adequate. Using any higher doesn't display enough board area. There are some types available with a built-in measuring facility. These are important for checking actual PCB pad and drill hole sizes.
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  • Cut and Crop Tool
    • Also known as Cut and Clench or Cut and Crimp The tool automatically squashes the wire flat before cutting above it. This tool is used in the VIA Technique described later.

  • Heat Gun
    • This type of tool is required for removing (reworking) SMT components, This is the only tool that needs a certain amount of training to use successfully. This will be described later.

    • Heat Guns come in 2 forms:-

      • Paint Strippers
      • Hot Air Tools

    • Paint Strippers
      • These are relatively cheap and generate a wide column of very hot air with limited control over the air flow. These are more suited for removing the larger SMT devices or where heating a larger surface area of the PCB is required.
         
    • Hot Air Tools
      • These are designed to heat small areas and usually have a proper air velocity control to regulate air flow and thus the temperature. Thus these are more suited for removing the smaller SMT devices.

    • Generally though, as we're more interested here in a Low Cost solution, the techniques described later will be referring to the Paint Stripper type of tool.