TWI Industrial Member Report Summary 579/1996
S B Dunkerton and N R Matthews
As electronic devices get smaller, new techniques for assembly need to be examined.
Electronic devices continue to get smaller, and packages have increasing numbers of pins with a reduced pitch. Packages with a pitch of 0.5mm are already in use, and smaller pitches are becoming available. These trends in miniaturisation are presenting problems in assembly using conventional techniques such as mass reflow. For example, solder must be placed accurately, and there are increased problems with solder bridging between leads. Leads are fine and fragile, and it is more difficult to cope with a lack of coplanarity.
More tolerant connection techniques are needed in the foreseeable future. It is probable that the most promising route to fine pitch surface mount technology will be use of outward extending leads, such as gull wing, together with a soldering technique which will clamp the leads to the substrate board during processing. Hot bar/thermode heating and heating using a Nd:YAG laser are believed to be the most promising processing techniques.
- To evaluate and develop laser and hot bar/thermode soldering processes for attaching fine pitch components on to circuit boards and substrates.
- To compare these processes with state- of-the-art mass reflow, where possible.