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METHOD TO AFFIX & WAVE SOLDER IC CARRIERS ON A FLEXIBLE SUBSTRATE

IP.com Disclosure Number: IPCOM000005555D
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-15
Document File: 2 page(s) / 117K

Publishing Venue

Motorola

Related People

Jay Miniet: AUTHOR

Abstract

The goal of this article is to describe the steps required to affix and wave solder IC carriers on the top side surface of a flexible substrate.

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@ MOTOROLA

Technical Developments Volume 5 October 1985

METHOD TO AFFIX & WAVE SOLDER IC CARRIERS ON A FLEXIBLE SUBSTRATE

by Jay Miniet

ABSTRACT

The goal of this article is to describe the steps required to affix and wave solder IC carriers on the top side surface of a flexible substrate.

INTRODUCTION

   The electronic industry's present state-of-the-art method for IC carrier soldering on a rigid substrate employs the screening or stencilling of preformed solder paste on an IC foot-print or geometrical pad pattern. The IC carrier is positioned either manually or automatically on the substrate surface and then the assembly is reflowed with an IR system or a similar technique. This process must be repeated if components are to be used on both sides of the substrate. On the other hand, the capillary wave solder method not only permits the affixing of IC carriers on the flexible substrate topside surface, but also it allows the attachment of surface mount devices on the flexible substrate bottom-side surface, making it possible to wave solder the components on both surfaces at the same time.

PROCEDURE

Taking advantage of the flexible polyimide Kapton material, we have achieved a design stage never experienced in the electronic industry. We have a material thin enough to induce the use of a capillary soldering technique.

   Let us take a circuit design (see drawing) using several IC carriers. The IC carrier has 18 connecting pads. These pads are ,050 inch centers on four sides. The IC carrier area is about .30 square inches. No corner pads are recommended with this thin material. The IC carrier foot print is similar to a hybrid layout, but with the unique difference of plated thru vias matching the locations of the IC wall crevices. On the flexible substrate bottom-side surface, the vias are found to have a minimum pad diameter and a big diameter aperture. The rest of the com- ponents are SMC's, including resistors, capacitors and transistors, as well as diodes in SC%23 packages. Due to circuit criteria, only leaded components packages are available for some capacitors and one crystal.

   The placement of the IC carrier is accomplished with the assistance of a IC nestle-tool fixture. This fixture provides recesses to secure the IC carrier in place. It is recommended for a better alignment, that JEDEC IC packages be used. This fixture is keyed up to the flexible substrate internal tooling holes. Also, these tooling holes are used to key up the SMC's auto-placement machine.

The SMC's will be the first phase of the flexible substrate assembly. The devices will be adhered to the f...