Fishing – trapping – and vermin destroying
Patent
1987-12-29
1989-08-15
Hearn, Brian E.
Fishing, trapping, and vermin destroying
437219, 26427611, 357 74, 29848, 29856, H01L 2156
Patent
active
048574830
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the encapsulation of integrated circuits.
2. Description of the Prior Art
Certain users of integrated circuits wish to be supplied with circuits in the form of continuous flexible strips (in rolls) bearing these integrated circuits.
This makes it easier for these users to automate the mounting of these integrated circuits on printed circuit boards or on other supports. This is especially the case with integrated circuits designed for surface-mounting. The surface-mounting of components is a type of mounting be automated far more easily than the mounting of components by insertion in holes drilled in printed boards.
Surface-mounting machines are fed with components in the form of coiled strips that carry components. These strips are carried forward step by step as with a cinematographic spool. It is only when the individual component is being mounted on a printed circuit that it is separated from the rest of the strip.
There are two main types of manufacturing processes for integrated circuit chips.
In the first type of manufacturing process, a cut-out metallic leadframe (a copper leadframe for example) is used as a supporting strip is used. For each component position, this leadframe has, firstly, a socket to receive an integrated circuit chip and, secondly, individual conductors, which act as external connection pins for the integrated circuit. To make the leadframe retain sufficient mechanical strength, the conductors forming the external pins are connected to one another by elements of the leadframe and they are therefore short-circuited with respect to one another. It is only when an individual component is being detached in order to be mounted that the pins are unshorted by sectioning the elements which connect the conductors to one another.
In the second type of manufacturing process, a dielectric film (generally a polyimide) is used as the supporting strip. On this support, a pattern of thin film conductors is formed. Here again, these conductors here again act as external pins for the component when it is being mounted on a printed circuit. The conductors are printed on the dielectrical film. Hence, it is the dielectrical film that gives them mechanical strength, even if, in certain places, this film has openings over which the conductors pass. It is not necessary to provide for joining elements between the various conductors to ensure their mechanical rigidity.
In practice, there are two major problems here. The first problem relates to the testing of the integrated circuits and the second relates to their protection.
As regards the test, with strips made from a cut-out metallic leadframe it is impossible, in principle, to test the circuits so long as they are on the strip since their pins continue to be short-circuited until they are separated into individual components. The test (on the wafer) can be done on the integrated circuit chip before this chip is fixed to the leadframe and connected to the conductors of this leadframe. The test could also be done after separating an individual component when it is mounted on a printed circuit, but that would be to late since it is preferable to supply the user with rolls of already-tested components.
Moreover, this is one of the reasons why there is a need felt for mounting the integrated circuits on dielectric films because, in this case, the pins are not short-circuited and the circuits can be tested on the strips.
With respect to the problem of protecting integrated circuits, these circuits are known to be chemically and mechanically very fragile and it is obviously out of the question that a user should be supplied with a strip of integrated circuits in which the circuit chips are not protected in one way or another against mechanical shocks, corrosive agents and, if necessary, against electromagnetic radiation.
For strips made from a conducting leadframe, this raises no problem: the protection is got by encapsulation in a thermosetting resin. The technique is t
Labelle Jean
Steffen Francis
Hearn Brian E.
Pawlikowski Beverly A.
SGS-Thomson Microelectronics S.A.
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