Surface mount assembly (SMT) carries a crucial role to learn in the New Product Introduction (NPI) process for electronics manufacturing.
The top degree of automation inside the SMT methodology provides a number 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 to have an electronics manufacturing services (EMS) provider might be broken down into four key stages:
Solder Paste Printing
Pick make
Oven Profiling
Automated Optical Inspection (AOI)
Depending on the complexity with the design, or maybe your own outsourcing strategy, your product or service could pass through each of these processes subsequently, or you might discover that you just omit one step or two.
We should highlight the specific attributes, along with the vital importance, in the solder paste printing process on your NPI.
Working to your specifications
Step one for the EMS provider is to analyse the pcb (PCB) data that is certainly specific to your order, to ensure they select the required stencil thickness and the most suitable material.
Solder paste printing is among the most common approach to applying solder paste into a PCB. Accurate solder paste application is hugely crucial in avoiding assembly defects which could use a knock on effect further along the production process. Therefore it is vital that key stage is correctly managed and controlled from your EMS partner.
Solder paste is essentially powdered solder which was suspended in the thick medium called flux. The flux behaves as a form of temporary adhesive, holding the ingredients in place prior to the soldering process begins. Solder paste is used to the PCB utilizing a stencil (generally metal, but occasionally nickel,) then once the solder is melted it forms an electrical/mechanical connection.
The thickness in the stencil ‘s what determines the level of solder applied. For a few projects it may well be essential to have a lot of thicknesses in different areas inside one stencil (known as a multi-level stencil).
Another primary factor to take into consideration in the solder printing process is paste release. The right sort of solder paste should be selected in relation to the dimensions of the apertures (or holes) inside stencil. In the event the apertures are incredibly small, by way of example, then this solder paste could possibly be prone to adhering to the stencil and never adhering correctly on the PCB.
Controlling the rate of paste release however can be simply managed, either start by making changes to the style of the aperture or by reduction of the thickness with the stencil.
The solder paste utilized can also influence on the ultimate top printing quality, therefore it is vital that you choose the appropriate blend of solder sphere size and alloy to the project, and to make sure it is mixed on the correct consistency before use.
Ensuring quality
As soon as the stencil may be designed along with your EMS partner is ready to make the first PCB, they are going to next want to consider machine settings.
Basically, the flatter you can maintain the PCB with the printing process, the better the end result will probably be. So by fully supporting the PCB in the printing stage,either using automated tooling pins or which has a dedicated support plate, your EMS provider can get rid of the potential for any defects including poor paste deposit or smudging.
It’s also important to consider the speed and pressure of the squeegees throughout the printing process. One solution is going to be have one speed for the solder paste but to own varying degrees of pressure, depending on the unique specifications with the PCB as well as the entire squeegee.
Cleaning the stencils, both before and throughout production, will also be essential in ensuring qc. Many automatic printing machines have a very system which can be set to wash the stencil from a fixed number of prints which helps to prevent smudging, and prevents any blockages of the apertures.
Finally too, the printers needs to have a built-in inspection system (including Hawk-Eye optical inspection) that may be preset to observe the use of paste over the whole PCB after printing.
The solder paste printing process is really a precise and detailed the one which may significant part to experience inside the ultimate success of your respective new product. And, since this blog post highlights, a lot of detailed work is likely to occur behind the scenes before your EMS partner solders the initial electronic aspect of a board.