Abstract: A method of applying a tacking agent to a printed circuit board. The printed circuit board (10) has a number of solder pads (12), and each solder pad is preclad with a layer of solder (14) between 0.02 and 0.3 mm thick. A plastic film (16) is temporarily adhered to the printed circuit board by a pressure sensitive adhesive. The plastic film has a number of apertures (22) that correspond to the solder pads, and is positioned so that the apertures in the film expose the solder coated pads. There is a breakaway tab (20) on the plastic film that is used to peel the film from the printed circuit board in a later operation. The film is roller coated with a high viscosity tacking agent (30) so that a layer of the tacking agent is applied to the exposed interconnect pads. The plastic film is then peeled cleanly away from the printed circuit board using the breakaway tab, leaving the tacking agent only on the solder pads.

Abstract: A soldering process for use with solder clad printed circuit boards (10) uses a pin transfer means to apply a tacking agent to the substrate. An array of pins (24) is dipped into a film of tacking agent (22). The pins are removed from the tacking agent (26) carrying with them a predetermined amount of tacking agent. The pins are then contacted (27) to the printed circuit board and removed (28). During this process, a predetermined amount of tacking agent is deposited at selective locations on the printed circuit board. A component is placed (30) on the printed circuit board in the tacking agent and the circuit board and component are heated (40) in order to reflow the solder and effect the solder joint between the component and the board.

Abstract: A method for applying solder on a substrate (12) comprises the steps of providing a substrate (12) having predefined solder pads (15) and then providing solder spheres (16) for suitable placement on the solder pads. Then applying flux (14) and tacking media (18) between the solder pads (15) and the solder spheres (16) and then placing the solder spheres on the solder pads. Subsequently the solder spheres are heated onto the solder pads of the substrate providing reflowed solder (26) on the solder pads. Then a layer of flux tacking media (28) is applied on the reflowed solder. Next, a component (30 or 40) is placed on the reflowed solder and flux tacking media providing a substrate assembly (10). Finally, the circuit assembly is heated allowing the component to be soldered to the solder pad.

Abstract: A semiconductor device assembly comprises a semiconductor device (10) attached to a substrate (20). The substrate has a metallization pattern (22) on the surface and a polymeric film (24) covering most of the surface and the metallization pattern. A window-frame shaped opening (26) is created in the film, exposing portions of the substrate surface. The semiconductor device is attached to the substrate in such a manner that it lies in the interior perimeter (28) of the window-frame shaped opening in the film. An adhesive material (18) is applied to fill the space between the semiconductor device and the substrate. The window frame opening in the polymeric film serves to confine the adhesive to the area in the opening and underneath the device and prevents unwanted spread of the underfill material by forming an ideal fillet geometry. In another embodiment of the invention, the semiconductor device is in a package and the package is attached directly to the substrate.

Abstract: A method of soldering leadless components to a printed circuit board without using solder paste is disclosed. A thick layer of solder (42) is plated onto a printed circuit board (40), and an oxide layer (43) is formed by heating. Solder flux (45) is applied to those solder pads that are intended to be reflowed, and components (54) are placed. The printed circuit board is heated, and a solder joint (68) is effected between the components (54) and the circuit board (40), while the unfluxed solder pads (66) do not reflow and remain flat. Solder flux is then applied to the remaining solder pads (66) on the same or the opposite side of the circuit board. Additional components (77) are placed, and the circuit board (40) is reflowed a second time.