DESIGN AND PROCESS DEVELOPMENT FOR THE ASSEMBLY OF 01005 PASSIVE COMPONENTS

摘要

Growing demands for smaller electronic assemblies hasrnresulted in reduced sizes of passive components,rnrequiring the introduction of newer components, such asrnthe 01005 devices. Component miniaturization presentsrnsignificant challenges to the traditional surface mountrnassembly process. A successful assembly solution forrnthese 01005 devices should be repeatable andrnreproducible, and should include guidelines for (i) thernselection of solder paste and (ii) appropriate stencil andrnsubstrate pad design, and should ensure strict processrncontrol standards.rnDuring the first phase of this study, different stencil types,rnaperture designs, pad layouts and process parameterrnsettings were evaluated with the goal of achieving a highyieldrnassembly solution for 01005 components. Printedrncircuit board assemblies are populated, usually, with bothrnlarge active devices (often surface mount packages),rnalong with much smaller passive components (such asrn01005s). Consequently, it was decided to use a 4 milrnthick stencil along with a type 4 solder paste. Based onrnthese process and design conditions, several stencilrnaperture shapes were evaluated using metrics, such asrntransfer efficiency and variance in volume of therndeposited solder. These two criteria help determine solderrnvolume adequacy and consistency. In addition, differentrnpad layouts were studied vis-à-vis their ability to promotern(or inhibit) component self alignment during the solderrnreflow process.rnThe results of the first phase of this study indicated thatrnan electroformed stencil performed much better than arnlaser cut stencil in terms of transfer efficiency. However,rnconsidering the relatively higher cost of an electroformedrnstencil, a follow up (second) study focusing on the use ofrna laser cut stencil was considered essential. The objectivernof this study was to develop a process that providesrnhigher yields while ensuring cost effectiveness. Aperturerndesigns were adjusted to increase the area ratio. Thernresults showed that it was possible to develop a robustrn01005 assembly process with the use of 4 mil thick laserrncut stencil in concert with a type 4 solder paste.