Copper Plating Bath Analysis and Control A copper plating bath is a working solution that changes as it is used, and the changes are not visible in the appearance of the deposit until they are advanced. The analysis and the additions that keep the bath in its window are the…

Assembly Process Capability and Control Charts A capability index compares the spread of a process with the tolerance it has to meet. A control chart shows whether the process has moved. The two answer different questions and both are needed. What Capability Answers The index compares the process spread with…

Reflow Profile Development and Control A reflow profile is the temperature history the assembly experiences as it passes through the oven, and it decides whether the solder forms a sound joint or merely melts. Building one is an exercise in satisfying several constraints at once: the alloy needs to reach…

Paste Volume and Print Verification Paste volume is the single largest influence on solder joint quality, and it is also the variable that a production line can measure most easily. Every joint on the board begins as a printed deposit whose height, area and shape decide how much solder will…

Desoldering and Rework Techniques Compared Every assembly eventually needs a joint remade. Removing solder is a different problem from adding it, because the joint has to be heated through a board that may already be populated, and the surrounding material has seen at least one thermal cycle. The methods differ…

BGA Solder Ball Alloy Selection A ball grid array package carries its own spheres, pre attached by the component supplier, and the assembly process joins those spheres to pads with paste. The alloy of the ball and the alloy of the paste are therefore two separate choices that meet at…

Controlled Impedance: Preparation, Placement and Process Control Controlled impedance turns a geometric feature into an electrical specification. A trace of a given width, on a given layer, above a given reference plane has a characteristic impedance, and the design says that impedance must stay within a tolerance. Making that true…

Solder Mask Thickness and Its Effect on Assembly Solder mask is drawn as a two dimensional pattern, but it is printed as a three dimensional layer. Its thickness decides whether the mask can cover a tall trace, whether a dam between two pads survives assembly and whether a via is…

Panel Utilization: Preparation, Placement and Process Control Printed circuit boards are made on panels and sold as boards, and the difference between the two is where a significant part of the cost lives. Panel utilization is the fraction of the panel that becomes product, and improving it lowers the price…

Thermal Shock Versus Thermal Cycling Tests Thermal shock and thermal cycling both expose a board to a temperature change, and they produce different failures because the rate of change is different. A test that is chosen for the wrong reason qualifies the wrong property. What Separates the Two A thermal…