Abstract:
A method of forming BGA interconnections having improved fatigue life is disclosed. In particular, a combination of mask-defined and pad-defined solder joints are selectively positioned within the BGA package. The mask-defined solder joints possess a high equilibrium height, which forces the pad-defined solder joints to elongate, thereby making the pad-defined solder joints more compliant. Further, the pad-defined solder joints posses a slightly longer fatigue life because the stress concentrations found in the mask-defined solder joints are not present in the pad-defined solder joints. Therefore, the fatigue life of BGA packages is increased by implementing a majority of mask-defined solder joints to maintain a high equilibrium height, and selectively placing pad-defined solder joints in high stress areas of the BGA package.
Abstract:
A printed circuit board includes a plurality of lands thereon. The size D2 of the outer land 3 in the direction along the outside array is less than the size D1 of the inner land 1 in the direction along the inside array. Therefore, it is possible to pass the pattern 4 with enough clearance against the outer land 3. The outer lands 3 are formed with an oval, elliptical or oblong shape. Namely, the size D3 of the outer land 3 in the direction perpendicular to the direction of the outside array is greater than the size D2. Then, it is possible to ensure a sufficient reliability of a soldered part. Preferably, the connected area 5 between the inner land 1 and the pattern 4 and the connected area 7 between the outer land 3 and the pattern 6 are formed as a shape of a tear-drop. Then, the patterns 4, 6 cannot be easily cut by a thermal stock or a heat cycle. The solder resist 8 is coated, around the outer land 3, from an outer area to an inner area of the outer land 3, except for the central area 3A. The resist 8 is further coated, around the inner land 1, from an outer area to an inner area of the inner land 1, except for the central area 1A. Then, each area 5, 7 is reinforced by the resist 8. Further, since a clearance between exposed areas 1A and a clearance between exposed areas 3A are widened, a bridge of solder does not easily occur.
Abstract:
A solder mask having a clover-leaf shaped opening around a PTH for enhanced performance. The solder mask resides on a surface of a printed circuit board comprising lands and PTH's. The opening around the PTH is configured to maintain a minimum channel width between the PTH and an adjacent land while maximizing the opening around the PTH, thereby decreasing the likelihood that the solder mask material will be inadvertently drawn into the PTH.
Abstract:
A printed circuit board is provided having a beveled edge for ease of insertion into a receptor. The beveled edge is extended onto the solder mask to present a contiguous beveled surface. Moreover, the PCB includes bonding pads which can be surface mounted with pins extending from the receptor. Each bonding pad includes a forward portion and a rearward portion. The forward portion is covered with the solder mask layer to present a smooth surface channeled inward in a V-shaped configuration. The forward portion channels or directs the pin along a central axis near the apex of the V-shaped forward portion onto the upper surface of the bonding pad rearward portion. Accordingly, the pin is channeled to an area absent solder paste along the central axis such that during subsequent reflow operation the solder paste is reliably extended over and around the centrally placed pin.
Abstract:
A method for producing an electronic part mounting structure in which electronic parts such as IC packages are electrically connected to the surface of a printed circuit board utilizes a low-melting point metal. More particularly, the method provides an electronic part mounting structure capable of sufficiently and assuredly supplying solder to a portion between the terminal of a printed circuit board and the leads of an electric part while maintaining a predetermined thickness required to connect the printed circuit board and the electronic part to each other. By arranging the structure such that a gap, in which a solder layer having a predetermined thickness can be formed between the terminal of the printed circuit board and the lead of the electronic part to be connected to the terminal, is formed, the solder required to solder-connect the two elements can be sufficiently and assuredly supplied to the gap. Therefore, a reliable solder connection can be established.
Abstract:
A process for reflow mounting an electronic component includes coating a terminal electrode on a mounting board with a second solder having a second melting point higher than a reflow temperature, placing the mounting board with the electronic component on a mounting land on a conveyor which may be brought into contact with the second solder on the terminal electrode, and heating the mounting board to the reflow temperature. The terminal electrode may be coated with a solder repelling material at a selected dividing area effective for dividing the terminal electrode into a plurality of sections substantially isolated from each other in terms of solder flow. Alternatively, a mounting jig may be used for supporting the mounting board without bringing the second solder on the terminal electrode into contact with the mounting jig.
Abstract:
Disclosed is a method of providing solder on selected portions of a printed circuit board. Solder is first electroplated over copper conductor patterns on the board by means of a first photoresist layer. After stripping the first photoresist, a second photoresist layer is laminated over the board and developed to expose selected portions of the solder. The exposed portions are selectively stripped. The copper exposed by the selective stripping is then subjected to a scrubbing while the photoresist protects the remaining solder, and the second photoresist is removed.
Abstract:
Movement of surface mount components during soldering onto TEFLON.TM. printed wiring boards is prevented by applying a strip of solder mask material to a solder pad to define a component lead area and applying solder to areas of the areas of the solder pad not covered by the solder mask strip. Solder paste is applied to the component bad area and the surface mount component is positioned with a lead in registry with the component lead area. The entire board is then heated to mechanically and electrically adhere the component lead to the pad.
Abstract:
A printed circuit board has a copper foil pattern formed thereon in the shape of exclamation marks oriented in the direction of solder flow such that undesirable peelback effects can be isolated and the amount of solder attached to the pattern can be uniformly controlled.
Abstract:
A circuit board having apertures within which circuit component leads are soldered and having a surface coated with solder resist in a universal pattern. The solder resist coating intersects the periphery of the apertures to alter the temperature environment in the aperture during the soldering process, preventing the formation of solder fillets at the board surface and permitting gasses to escape from the apertures.