Apparatus for real-time estimation of printing medium properties and

Abstract

The apparatus may be used with printing apparatus in which a media spreading member, such as a squeegee, moves relative to a surface, causing printing medium to be moved across said surface. The printing medium can be electrical solder paste and the surface can be a stencil. The apparatus is used for measuring linking parameters that are related to mechanical properties of the printing medium and the printing environment, such as viscosity and coefficient of friction. The apparatus comprises means for measuring a machine parameter that represents the force experienced by the media spreading member and means for resolving the measured force parameter into components equivalent to two orthogonal components, typically normal to the surface and tangential to it in the direction of relative motion. The apparatus also includes means for measuring a machine parameter that represents the velocity of the media spreading member relative to the surface. Means are also provided for measuring the linking parameters by determining a specific instance of a predetermined general relation among the measured machine parameters of velocity, first force component and second orthogonal force component and the linking parameters. The means for determining a specific instance of a relation may include means for comparing at least three sets of associated measured machine parameters and, based on the comparison, identifying a relationship that shows agreement with all of the sets of measured machine parameters within a predetermined level of accuracy. A typical such means for identifying such a relationship is an apparatus that applies a least squares relationship selecting technique. Suitable general relationships for Newtonian and non-Newtonian fluids may be used. A method is also disclosed.