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Enhanced Double-sided Surface Mounted Assembly

IP.com Disclosure Number: IPCOM000041201D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bakos, P: AUTHOR [+2]

Abstract

An improved method is disclosed for double-sided surface mountings that improves the reliability and allows multiple rework capability. Surface mounting of components is facilitated by screening a solder paste on the circuit board through a mask. The components are then transported by a pick-and-place machine to the board and placed onto the screened paste pattern. The component, paste and substrate are heated until the solder melts and reflows. The assembly is then allowed to cool to ambient temperature to obtain adequate bonds between the component leads and the pads. Because the screened paste is wet during component attachment, only one side of the circuit board can be populated with components at a time.

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Enhanced Double-sided Surface Mounted Assembly

An improved method is disclosed for double-sided surface mountings that improves the reliability and allows multiple rework capability. Surface mounting of components is facilitated by screening a solder paste on the circuit board through a mask. The components are then transported by a pick-and-place machine to the board and placed onto the screened paste pattern. The component, paste and substrate are heated until the solder melts and reflows. The assembly is then allowed to cool to ambient temperature to obtain adequate bonds between the component leads and the pads. Because the screened paste is wet during component attachment, only one side of the circuit board can be populated with components at a time.

To perform double-sided surface mounting, a suitable adhesive must be used to secure the components to the board during the solder reflow process. Some of the requirements of the adhesive are that it be a thermally conductive, high temperature, electrically insulating and removable adhesive to permit component rework.

A dry, Vacrel resist film with a top layer of polyester and a bottom layer of polyolefin is used as the adhesive. The polyester film and the polyolefin is removed and the inside resist film is folded into an adhesive media of the desired thickness. The folded film is placed on the component between the leads and dried at room temperature. The component with the resist adhesive is then placed onto t...