Abstract: A sequential electrochemical reduction method and apparatus are provided for assessing and restoring solderability of electronic component leads. The method detects and quantifies the presence of metallic oxides that are detrimental to solderability by sequential electrochemical reduction in contact with an electrolyte in an inert atmosphere. A cathode having a high hydrogen overvoltage is placed in contact with the electrolyte. A solderable portion of the component to be tested is placed in contact with the cathode and the electrolyte. An inert counter electrode and a reference electrode are also placed in contact with the electrolyte. A current is passed between the cathode and inert electrode, and the voltage and current are measured as a function of time during reduction of metallic oxides on the solderable portions of the component.

Abstract: Apparatus for assessing solderability of electronic component leads and printed wiring boards by sequential electrochemical reduction. The apparatus detects and quantifies the oxides present on copper, solder, andintermetallics that are detrimental to solderability. A solderable portion of the component to be tested is immersed in an electrolyte to form an electrode. An inert counter electrode and a reference electrode are also placed in the electrolyte. A current is passed from the inert counter electrode to the tested component, and the potential between the component and the reference electrode is recorded as a function of time. In a plot of the electrode potential versus the total charge passed, a series of inflection points identify and quantify particular metallic oxides present on the solder. The plot is compared with previous analyses of aged specimens having known oxide compositions that correlate with degradation of solderability.

Abstract: A system is provided for regenerating reducing agents used in ancillary chemical or electrochemical processes such as restoring solderability of electronic components. The system includes a cathode, an anode, and an electrolyte system that is separated by a semipermeable ionic barrier into a catholyte and an anolyte. The catholyte includes the reduced member of a redox couple, which can be regenerated electrochemically. The redox couple of the electrolyte system is charged like a battery and discharged during the ancillary process. Regeneration of the reduced member of the redox couple is accomplished at the cathode. The cathode comprises an electrode having a high hydrogen overvoltage so that sufficiently negative potentials can be attained while minimizing hydrogen evolution. Chemical balance is maintained by the semipermeable ionic barrier, which permits proton migration from the anolyte to the catholyte but acts as a barrier against diffusion and migration of cations from the catholyte to the anolyte.

Abstract: A sequential electrochemical reduction method and apparatus for assessing solderability of electronic component leads and printed wiring boards. The method detects and quantifies the oxides present on copper, solder, and intermetallics that are detrimental to solderability. A solderable portion of the component to be tested is immersed in an electrolyte to form an electrode. An inert counter electrode and a reference electrode are also placed in the electrolyte. A current is passed from the inert counter electrode to the tested component, and the potential between the component and the reference electrode is recorded as a function of time. In a plot of the electrode potential versus the total charge passed, a series of inflection points identify and quantify particular metallic oxides present on the solder. The plot is compared with previous analyses of aged specimens having known oxide compositions that correlate with degradation of solderability.

Abstract: A roughened surface of a conductive substrate, such as copper, provides uniform Sn-Pb solder coatings and improved solder retention at printed wiring board (PWB) plated through-hole rims (knees) and surface pads during solder dipping or reflow. A high density of copper surface features of moderate average roughness provides the most favorable solder coating thickness distribution. Various chemical or electrochemical etching processes may be used to produce the desired copper surface topography. Reflowed solder thickness distribution in a PWB knee region attained with a ferric chloride copper etching process peaks at 4 .mu.m, which provides a good margin of safety for preventing exposure/oxidation of the underlying Cu-Sn intermetallics. The ferric chloride copper etching process yields only 1% of solder thickness measurements in the undesirable 0-1.5 .mu.m range for plated through-hole rims. Copper surface roughening is expected to greatly reduce solderability loss in mass produced PWBs.

Abstract: A low-temperature, nondestructive method of electrochemical reduction is provided for restoring solderability of oxidized electronic component leads and solderable portions of printed wiring boards. The component or circuit board is immersed in an electrolyte solution. The electrolyte is chosen to be non-reactive with the circuit board and component materials. In one embodiment, the electrolyte comprises a benign borate buffer solution. The solderable portion of the component or circuit board is connected to the cathode of an electric power source to form a first electrode. A second, inert electrode is connected to the anode of the current source and immersed in the electrolyte. Current passing between the electrodes electrochemically reduces the metallic oxides on the solderable portions of the component or circuit board. In a second embodiment, the electrolyte comprises an active reducing agent.