Ball grid array probing technique

A printed circuit assembly, comprising:

• a printed circuit board having a front side and a back side, the printed circuit board having at least one electrically conductive via formed therein, said at least one electrically conductive via extending from the front side of said printed circuit board to the back side of said printed circuit board;
• a ball grid array package having an electronic circuit contained therein, said ball grid array package being mounted to the front side of said printed circuit board so that at least one circuit node of the electronic circuit is electrically connected to said at least one electrically conductive via;
• at least one probe pad formed on the back side of said printed circuit board, said at least one probe pad being electrically connected to said at least one electrically conductive via, said at least one probe pad also being laterally displaced from said at least one electrically conductive via, said at least one probe pad being located in a predetermined pattern on the back side of said printed circuit board and corresponding to a predetermined signal to be sampled;
• at least one ground pad formed on the back side of said printed circuit board, said at least one ground pad being electrically connected to a ground plane contained on said printed circuit board;
• a solder mask layer deposited on the back side of said printed circuit board, said solder mask layer having at least one probe pad aperture formed therein and at least one ground pad aperture formed therein, said at least one probe pad aperture in said solder mask layer being substantially aligned with said at least one probe pad so that said at least one probe pad is exposed by said at least one probe pad aperture formed in said solder mask layer, said at least one ground pad aperture in said solder mask layer being substantially aligned with said at least one ground pad so that said at least one ground pad is exposed by said at least one ground pad aperture formed in said solder mask layer, said solder mask layer also covering said at least one electrically conductive via.

A printed circuit assembly, comprising:

• a printed circuit board having a front side and a back side, the printed circuit board having at least one electrically conductive via formed therein, said at least one electrically conductive via extending from the front side of said printed circuit board to the back side of said printed circuit board;
• a ball grid array package having an electronic circuit contained therein, said ball grid array package mounted to the front side of said printed circuit board so that at least one circuit node of the electronic circuit contained therein is electrically connected to said at least one electrically conductive via;
• at least one probe pad formed on the front side of said printed circuit board, said at least one probe pad being electrically connected to said at least one electrically conductive via, said at least one probe pad also being laterally displaced from said ball grid array package, said at least one probe pad being located in a predetermined pattern on the front side of said printed circuit board and corresponding to a predetermined signal to be sampled;
• and
• a solder mask layer deposited on the front side of said printed circuit board, said solder mask layer having at least one probe pad aperture formed therein, said at least one probe pad aperture in said solder mask layer being substantially aligned with said at least one probe pad so that said at least one probe pad is exposed by said at least one probe pad aperture formed in said solder mask layer.