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In-Situ Method to Monitor Lamination Flow

IP.com Disclosure Number: IPCOM000062163D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Gotro, JT: AUTHOR [+4]

Abstract

The proper flow of resin in the lamination of a multilayer printed circuit board is critical for a number of subsequent operations. Because resin flow is dependent on a variety of conditions that can cause problems, the monitoring of the platen displacement and its alignment, that are used in the lamination process, provides a method of identifying flow variations for corrective action. Lamination is a squeezing flow geometry. A schematic of the geometry is given in Fig. 1.

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In-Situ Method to Monitor Lamination Flow

The proper flow of resin in the lamination of a multilayer printed circuit board is critical for a number of subsequent operations. Because resin flow is dependent on a variety of conditions that can cause problems, the monitoring of the platen displacement and its alignment, that are used in the lamination process, provides a method of identifying flow variations for corrective action. Lamination is a squeezing flow geometry. A schematic of the geometry is given in Fig. 1. If only polymer flows during lamination (assuming negligible glass deformation), the flow can be expressed in terms of the change in thickness: (1)

(Image Omitted)

where 2h0 and 2hf are the initial and final thicknesses, pP is the polymer density, and p0 is the prepreg density given by:

(Image Omitted)

where MP is the mass fraction of polymer in the prepreg (also called pick-up), and pg is the density of the glass cloth. Equation (1) may be used to calculate the flow number continuously during lamination by monitoring the thickness variation with time, where 2h(t) is the thickness at any time t. (2)

(Image Omitted)

If the plate separation changes sufficiently slowly so that a quasi-steady-state condition is achieved, and stress overshoot and inertial terms may be neglected, and the viscosity can be approximated as Newtonian, the rate of plate motion is given by the following equation: (3) where F is the compressive force, R is the radius (or equivalent radius) of the sample, and h is the viscosity. At constant force, this equation can be integrated to obtain: (4) The flow number may now be cast in terms of the change in viscosity: By monitoring the platen displacement during lamination, both flow number and viscosity data can be obtained. The principle of operation for the capacitance sensor may be understood by examining the general capacitor equation: C = K* (A/D) where C is the capacitance, K is the dielectric constant of the medium, A is the area of the capacitor, and D is the capacitance of the gap. For a given medium (air in this case) and capacitor (the sensor device), K and A are fixed. Hence, the capacitance C is inversely proportional to the sensing gap D. In practice, the capacitance voltage V is m...