Surface mount assembly (SMT) includes a crucial role to play from the New service Introduction (NPI) process for electronics manufacturing.
The top degree of automation from the SMT methodology supplies a variety of advantages, from automatic correction of errors, to simpler and faster assembly, better mechanical performance, increased production rates and reduced labour costs.
The SMT assembly process on an electronics manufacturing services (EMS) provider might be separated into four key stages:
Solder Paste Printing
Automated Optical Inspection (AOI)
With respect to the complexity from the design, or maybe your own outsourcing strategy, your products or services could move through each one of these processes consequently, otherwise you may find which you omit a measure or two.
We want to highlight the precise attributes, and the vital importance, of the solder paste printing process for the NPI.
Attempting to your specifications
The first task for your EMS provider is to analyse the printed circuit board (PCB) data that is certainly specific to your order, to ensure that they pick the required stencil thickness and the most suitable material.
Solder paste printing is easily the most common technique of applying solder paste to some PCB. Accurate solder paste application is hugely critical in avoiding assembly defects which may use a knock on effect further around the production process. Therefore it is vital that key stage is correctly managed and controlled through your EMS partner.
Solder paste is basically powdered solder that is suspended in a thick medium called flux. The flux provides for a form of temporary adhesive, holding the constituents in position prior to the soldering process begins. Solder paste is applied for the PCB employing a stencil (generally metal, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness from the stencil ‘s what determines the volume of solder applied. For many projects it may well even be important to have several thicknesses in numerous areas within the one stencil (sometimes called a multi-level stencil).
Another main factor to take into account inside the solder printing process is paste release. The correct kind of solder paste must be selected based upon how big the apertures (or holes) from the stencil. When the apertures are very small, as an example, then your solder paste might be prone to adhering to the stencil rather than adhering correctly to the PCB.
Manipulating the rate of paste release however can be managed, either by causing changes to the design of the aperture or by lessening the thickness with the stencil.
The solder paste that is used also can impact on the last print quality, so it is imperative that you pick the appropriate combination of solder sphere size and alloy for your project, also to make sure it is mixed on the correct consistency before use.
As soon as the stencil continues to be designed along with your EMS partner is preparing to produce the first PCB, they will next be considering machine settings.
Quite simply, the flatter you can the PCB with the printing process, better the final results will probably be. So by fully supporting the PCB throughout the printing stage,either by the use of automated tooling pins or having a dedicated support plate, your EMS provider can get rid of the chance of any defects such as poor paste deposit or smudging.
You’ll want to take into account the speed and pressure from the squeegees throughout the printing process. One solution is to have one speed for that solder paste but to own varying examples of pressure, depending on the unique specifications with the PCB and also the whole squeegee.
Washing the stencils, both prior to and throughout production, is likewise crucial in ensuring qc. Many automatic printing machines use a system that could be set to completely clean the stencil after having a fixed amount of prints which assists in order to avoid smudging, and prevents any blockages with the apertures.
Finally too, the printers should have a built-in inspection system (like Hawk-Eye optical inspection) that may be preset to evaluate the existence of paste across the whole PCB after printing.
The solder paste printing process is really a precise and detailed the one that will have a significant part to learn in the ultimate success of your respective new service. And, simply because this short article highlights, a lot of detailed work is planning to occur behind the scenes before your EMS partner solders the very first electronic aspect of a board.