SERIGRAPHY PROCESS IMPROVEMENT

Publishing Venue

Motorola

Related People

Abstract

This concerns an improvement in a serigraphy process used to dispense solder paste on a PCB (Printed Circuit Board). The solder paste is manual- ly placed along a scraper. The paste is introduced in the openings of the serigraphy screen and thus, is deposited on the PCB through the moving scrapes (Figure I).

MOTOROLA Technical Developments

8

SERIGRAPHY PROCESS IMPROVEMENT

by Bertrand Bourreau, Denis Ferron and Gabriel Fouchereau

  This concerns an improvement in a serigraphy process used to dispense solder paste on a PCB (Printed Circuit Board). The solder paste is manual- ly placed along a scraper. The paste is introduced in the openings of the serigraphy screen and thus, is deposited on the PCB through the moving scrapes (Figure I).

This process has two disadvantages:

  The solder paste is held back by a plastic baffle situated on each side of the scraper (Figure 2). The quantity of wasted paste is reduced considerably due to the fact that the baffles are out-of-line so that a baffle can receive the solder paste wasted by the opposite baffle (Figure 3).

This improvement has two advantages:

. Cost: No more dry paste is wasted.

Quality: Since there is no dry paste, the reflow process is improved.

  The baffles have been made without sharp cor- ners in order to provide for easy cleaning of the scrapers (see the rounded baffles-Figure 4). This improvement is applicable to any type of serigraphy arrangement.

  Some of the paste collects on each side of the scraper when moving, keeps still and dries rapidly. This may represent up to 50% of the paste initially placed on the scraper.

Frequently, the operator has to add solder paste under the scraper to compensate for the loss of paste that appears on each side of the scraper.

* The improvement implemented consists of par- tially h...