- Higher throughput including multi-height deposits
- Ability to dispense glue patterns with one pass of the squeegee
- Precise deposits with no blockages
- Stencils are easy to clean
- Glue dot programming is effected off-line using simple guidelines
The stencil technology differs from that used to print solder paste, where the intention is to transfer the entire contents of the aperture onto the PCB. When glue printing, good use is made of the adhesive's ability to remain as a partial retention in the apertures. This is based on the simple relationship of the surface area of the deposit base (PCB contact area) relative to the aperture wall surface area (see diagram below).
Where apertures are small, for example 0.3mm (0.012"), the adhesion between the glue and stencil effectively retains some of the deposit and the resultant dots have a small or low Glue Dot Height (GDH).
Stencil apertures of 0.8mm (0.032") ensure a larger percentage of the adhesive is transferred onto the PCB. When the stencil and board are separated the stencil drags the adhesive and the resultant dots will be higher.
For apertures of between 1.5mm to 2mm (0.060" to 0.080") most of the adhesive is transferred onto the PCB and the GDH will be similar to the thickness of the stencil.
Each of the adhesives currently available have individually distinct properties and characteristics which may require some process variations. Most manufacturers offer guidelines and basic design rules to ensure compatibility with screen printing.
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