Patent Application
20050239237
This application claims priority to German Patent Application Serial No. 102004020580.9, filed Apr. 27, 2004, and which is incorporated herein by reference in its entirety.
The invention relates to a method for producing a BGA chip module. The invention also relates to a BGA chip module with a carrier, a chip arranged on an upper side of the carrier and bonding points on the underside of the carrier.
BGA stands for Ball Grid Array and refers to chip modules which have their bonding points arranged in the form of a grid on the underside of the module. It is customary for example to provide 64 bonding points in a grid spacing of 1.5 mm, 1.27 mm or 1 mm with a diameter of the “balls” of about 0.6 mm.
BGA chip modules of this type are known from, for example, the textbook by Wolfgang Scheel (editor): Baugruppentechnologie der Elektrotechnik, Verlag Technik, Berlin, first edition 1997. The chip, the term chip being used for integrated circuits, is mounted in a standard package. The bonding points of the chip must be connected to bonding points on the underside of the module during the production of a BGA chip module. It is known to use a carrier which has via holes, through which chip terminals are connected to terminal pads on the underside of the module. Solder balls are applied to the terminal pads of the underside, so that the terminal pads can later be connected to a printed circuit board.
The disadvantage of this method is that generally expensive, multilayered printed circuit boards have to be used, in particular if there are relatively great requirements for reliability, for example relatively great thermal or thermomechanical loads are to be withstood without damage. This makes BGA chip modules of this type expensive, since many wiring interposers and via holes are required to lead the terminals to the correct point.
An object of the invention is to provide a method for producing a BGA chip module which is less expensive to produce. Furthermore, a BGA chip module which can be produced at low cost is to be provided.
This object is achieved by a method for producing a BGA chip module with the steps of providing a carrier, forming holes at points of the carrier at which bonding points of the BGA chip module are to be produced, forming metallization areas on an upper side of the carrier and covering the holes, connecting bonding points of a chip to the metallization areas, and introducing bonding elements into the holes.
With respect to the chip module, the object is achieved by a BGA chip module of the type stated at the beginning, wherein the carrier has through-holes, which are covered on the upper side by metallization areas, the metallization areas being electrically connected to bonding points of the chip and bonding elements being accommodated in the holes.
The invention is explained in more detail below on the basis of an exemplary embodiment. In the drawings:
An advantage of the method according to an exemplary embodiment of the invention is that the forming of holes in a carrier can be implemented very inexpensively, for example by punching. The application of metallization areas is likewise a low-cost production step. The same applies to the introduction of bonding elements into the holes from the underside of the carrier. Consequently, the overall method comprises low-cost production steps using low-cost starting materials. In comparison with the method according to the prior art, it dispenses with the use of expensive multilayered printed circuit boards which have via holes. It likewise dispenses with the method step of applying terminal pads. These are replaced by the bonding elements which are fitted into the holes.
In an advantageous embodiment, the bonding elements are solder balls. These are of such a size that on the one hand they touch the metallization areas arranged on the upper side of the carrier and on the other hand they protrude beyond the surface of the underside, in order in this way to form the “balls” of the ball grid array.
It is also inexpensive to use an epoxy film as the carrier. This costs little and is easy to process. The method steps and machines required for this are known from the production of chip card modules and therefore do not present any technological problems.
The holes have been formed at points at which there are later intended to be bonding points of the finished BGA chip module 1. The metallization areas 4 therefore have, if need be, the form of interconnects, in order to allow on the one hand bonding at a favorable point and on the other hand provision of the bonding points of the BGA chip module at the specified point.
After the forming of the metallization areas 4, the holes 3 are closed on the upper side 5 of the carrier film 2. Solder balls 8 are then fitted from the underside 9, and are connected to the underside of the metallization areas 4 in the plane of the upper side of the carrier film 2. The size of the solder balls 8 is made to match the thickness of the carrier film 2 such that the solder balls 8 protrude beyond the underside 9 and so form “balls” of the “ball grid array”. There is later the possibility of mounting the finished BGA chip module 1 on a printed circuit board and connecting it to the latter mechanically and electrically by melting of the solder balls 8.
On the upper side 5 of the carrier film 2, the arrangement enclosing the chip 7 is provided with a covering layer 12, which is formed for example by injection molding or as a glob top.
The embodiment represented is a carrier film 2 with metallization on one side. However, it is also within the scope of the invention to use a carrier film 2 with metallization on both sides, if this is necessary to provide further connection possibilities.
In the exemplary embodiment shown in
The BGA chip module 1 is still in a carrier strip 13, so that it still has to be singulated by punching out.
As is evident from the use of a carrier strip, a customary reel-to-reel process can be used for the production of the BGA chip modules 1 according to the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 020 580.9 | Apr 2004 | DE | national |
