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Method for flux spray control

IP.com Disclosure Number: IPCOM000145889D
Publication Date: 2007-Jan-30
Document File: 4 page(s) / 70K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for flux spray control. Benefits include improved functionality, improved performance, and improved ease of implementation.

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Method for flux spray control

Disclosed is a method for flux spray control. Benefits include improved functionality, improved performance, and improved ease of implementation.

Background

      The purpose of spraying flux is to spray a thin layer of liquid flux onto the bump areas of a flip chip substrate. Over-spraying can occur in the keep-out zone (KOZ) of the substrate during the spray flux process due to the poor control of flux spraying. The over-spraying contaminates the adjacent solder paste, interrupts the underfill (UF) flow pattern, and causes uneven flux distribution. Material waste, voiding, and electrical failure can result.

      Conventionally, a cone-shaped spray nozzle is used to spray a liquid flux. However, due to the poor control of the spraying process, a flux is often over-sprayed outside the substrate bump areas (see Figure 1).

General description

      The disclosed method is flux spray control. Charged moving particles/droplets exert magnetic force (Lorentz force) that is vertical to the moving direction of the particles/droplets. The force is in proportion to the speed of the moving droplet (V), the charging quantity (Q), and the magnetic strength (B). Conventionally, the spray flux droplet is not charged during spraying (see Figure 2).Charged droplet/particles exert a Lorentz force in a magnetic field, enabling control of the flux spray pattern to solve the over-spay issue.

      The key elements of the disclosed method include:

•     Spray flux nozzle connected to a positive electrode to charge the flux droplet during spray

•     Specifically designed magnetic field to control the flux droplet during spray

•     Deionization of the substr...