Browse Prior Art Database

Circuit Boards With Directly Attached Chips

IP.com Disclosure Number: IPCOM000036259D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Related People

Funari, J: AUTHOR [+2]

Abstract

Circuit chips are conventionally attached to ceramic substrates which are subsequently attached to a circuit board. Direct attachment of the chip to the board eliminates a level of packaging reducing the package cost, increasing the computer speed, and lowering the probability of field failures.

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Circuit Boards With Directly Attached Chips

Circuit chips are conventionally attached to ceramic substrates which are subsequently attached to a circuit board. Direct attachment of the chip to the board eliminates a level of packaging reducing the package cost, increasing the computer speed, and lowering the probability of field failures.

The present method utilizes a pick/place/solder element containing both vacuum and forced hot gas, such as nitrogen. The element is used to pick up a chip from a supply station, move it to a designated X-Y location over a board, deposit the chip, and solder the chip.

The circuits for chip attachment are coated with a chromate solder barrier to prevent solder run-out, resulting in a good, high solder joint or connection when soldered. The circuit pads used to accept the chip contain a highly solderable copper surface protected by a

(Image Omitted)

layer of positive resist. During fluxing and soldering, the resist is lifted and disintegrates to reveal the clean copper surface that is easily soldered.

The process shown in Figs. 1 and 2 provides circuitization of the circuit board, application of a chromate coating as a solder barrier, utilization of positive resist to provide a solderable surface, and the use of pick/place/solder tool (Fig.
3) to facilitate direct chip attachment to circuit boards without degradation of the base laminate material.

Fig. 1b is a schematic representation of a chip, board and solder joint after each of the process steps (Fig. 1a) is performed. Positive working photoresist, such as Shipley Company's AZ-345 resist, is applied to a metallized board (step
1). The board is then photo processed by means of a print and etch process (step 2) to form printed circuits with the resist still intact. The board is then re- exposed and devel...