Method for the manual placement of bottom terminated leadless device electronic packages using a mated stencil pair
AssigneeBusiness Electronics Soldering Technologies, Inc.
InventorsRobert P. Wettermann, Hung Hoang, Raymond A. Cirimele
Life of this patent
Estimating the term…
Abstract
The present invention relates to a process for the rework of bottom terminated leadless devices as well as a pair of stencils for the manual reattachment of such devices (commonly known as a QFN, LGA or MLF packages). This process is used to remount these devices once they have been removed from the printed circuit board or placing new devices on an already populated PCB. It is also used to add bumps to the bottom side of an electronic device package or pads.
Claims15
A method for manually attaching a leadless device onto a printed circuit boards comprising the steps of:
- providing a matched pair of polyimide single use first and second stencils each having a pattern of apertures that corresponds to a pattern of contacts on a surface of the leadless device and a pattern of contacts on surface of the printed circuit board;
- aligning the apertures in the first stencil with the pattern of contacts on the leadless device and affixing the first stencil to the surface of the leadless device with an adhesive;
- manually squeegeeing solder paste into the apertures in the first stencil;
- reflowing the leadless device to attach the solder and produce solder bumps on the contacts on the surface of the leadless device;
- removing the first stencil from the surface of the leadless device;
- aligning the apertures in the second stencil with the pattern of contacts on the leadless device and applying the second stencil to the surface of the printed circuit board;
- manually squeegeeing solder paste into the apertures of the second stencil;
- and
- aligning the solder bumps of the leadless device into the filled apertures of the second stencil on the printed circuit board;
- and
- reflowing the leadless device and printed circuit board to attach the leadless device to the printed circuit board.
A method for manually reworking a pattern of contacts on a surface:
- providing a polyimide single use stencil having a pattern of apertures that corresponds to the pattern of contacts;
- aligning the apertures in the stencil with the pattern of contacts and affixing the stencil to the surface with the contacts with an adhesive;
- manually squeegeeing solder paste into the apertures in the stencil;
- reflowing the surface with the contacts to form solder “bumps” on the contacts on the surface;
- and
- removing the stencil from the surface.
A stencil set for use in attaching a leadless device having a pattern of contacts onto a printed circuit board having corresponding pattern of contacts comprising:
- a pair of polymide stencils each including a plurality of apertures in a pattern that corresponds to the pattern of contacts on the leadless device and the printed circuit board, each stencil having an adhesive on one surface thereof that is protected by a release liner, wherein the stencils are configured for a single-use application.
Dependencies are inferred from the claim text.