Development of a 68-Pin Multiple In-Line Package

A multiple in-line package (MIP) is described which consists of a 68-lead plastic chip carrier soldered to a copper-clad epoxy-glass printed wiring board adapter. This package was developed to provide a means for adapting chip carriers to dual in-line package (DIP) dominated circuit assemblies. Lead frame type pins in the adapter board provide for the connection between the MIP and its associated printed circuitry by conventional wave soldering. The MIP pin-out consists of four rows of 17 leads each. The leads are on a 0.25-cm (0.1-in) pitch and the rows are spaced at 0.76 cm (0.3 in) to conform to DIP standards. A high soldering process yield is assured by the proper preparation of the adapter board and the use of a batch assembly sequence for the chip carrier attachment. A thin solder coating provides a check on the copper solderability, extends shelf life, and temporarily secures the through-hole pins to the board. Stencil printing of solder paste provides the additional solder required for acceptable through-hole pin and chip carrier interconnects. Accurate placement of the chip carrier was found to be necessary, since no repositioning occurs during solder reflow. Extensive accelerated environmental testing was performed to determine the reliability of both the chip carrier and the MIP assembly. It is concluded that a level of reliability equivalent to that of existing plastic molded packaging technologies such as DIP's is achieved by leaded plastic chip carriers as well as such carriers mounted to MIP adapters. The thermal dissipative capability of a MIP soldered into a printed wiring board was determined to be 32°C/W in a room temperature natural convective environment. This can be reduced to 15°C/W with 900 ft/min forced air cooling.