How to reflect the role of spray tin process in the production of multilayer printed circuit boards?

PCB manufacturing can be divided into two main stages:fabrication and assembly. The surface finishing process inevitably joins them together, ensuring that there is sufficient adhesion between the bare board and the components for sustained performance and greater reliability.There are many different styles of PCB surface finishing, but for non-consumer equipment, spray tin stands out: as an extension of the solder material (and therefore the solder process), it can be easily integrated into all circuit board materials that use the same solder for bonding components to the bare board. to the bare board using the same solder. This advantage applies to both leaded and lead-free solders, making spray tin an indispensable and highly applicable solder treatment in PCB production.

The Role of Tin Spray in Manufacturing

The study of the tin spraying process is relatively simple: after a much-needed period of social contact with the molten solder, the panel can be blown away from the excess solder by an air stream through a plane-aligned air knife at temperatures above the melting point of the solder. After curing, the panel data be cleaned in time to remove the remaining flux, and then the student undergoes controlled baking to dry. The tin spray process technology can be carried out by either vertical or horizontal raise system designs, depending on the development of the solder deposition method method: for vertically aligned baths of molten solder or nozzle/roll configurations that simultaneously distribute solder to the top and bottom of the board. The horizontal as well as the process has several main advantages.

As an in-line process, it can be easily integrated with existing equipment such as pre-etching, washing and drying. By integrating several processes into one in-line system, the solder can be preheated simultaneously, thus reducing processing time and increasing throughput accordingly.

Because the effect of gravity is constant on each side of the board, multilayer pcb fabrication the solder surface is more uniform. In general, in-line systems reduce the number of people in contact with the panels, minimize defects associated with mishandling, and increase throughput.

Checking and addressing common tinning errors

The first advantage of spray tin for manufacturers is that the solder process is already so well characterized and integrated into PCB production that it is almost difficult to translate it into a surface finish. There is no need for x-ray fluorescence or destructive cross-sectional analysis, as a simple visual inspection is sufficient. The tin-sprayed surface should be silvery and shiny - just like a solder joint - with no visible signs of partial or incomplete solder joint wetting. The presence of an uneven tin sprayed surface is usually indicative of a number of potential process failures.

Thinning of the coating - Not enough solder was applied to cover the pad surface during application development.

Incorrect process parameters - some combination of flux, solder temperature, or panel tinning time results in a poor surface finish.

Removing too much solder - After the air knife removes most of the solder, the residual solder does not fully cover the pads given the surface tension.

Process Control of Tin Spray Surface Finishes

When intermetallic compounds are typically located between the solder layer and the copper liner layer, the lack of a tin spray coating exposes the intermetallic compounds to the atmosphere. While the presence of intermetallic compounds indicates process wettability, exposure to the atmosphere can seriously affect the solderability of the surface, so rework is considered. Therefore, PCB factorythe tin spray process must be controlled to ensure a uniform coating and minimal intermetallic growth to maximize the distance between surface solder layers. Since bare copper readily dissolves into the molten solder, process engineers and technicians need to monitor the settling of the metal in the molten pool and its fall to the bottom of the crucible due to its density. According to Le Chatterley's principle, this can be mitigated by unclogging the precipitation or slightly increasing the temperature and copper content of the solder bath to prevent copper dissolution and intermetallic compound precipitation in the panel.