Application selection depends on several criteria including areas such as material selection, volume of PCBs to be coated, budget, throughput speed, type of coverage required and ease of masking. Unfortunately, it can be a combination of factors that effect choice rather than individual factors and it is important to look at all the information collectively.
When quotations are prepared in our coating service, the first question that is asked is what material is to be used?
This can be critical since some coatings lend themselves to spray processing compared to dip and vice versa. For example, a moisture cure coating is not ideal for dipping since eventually the whole dip tank will cure which can be an expensive exercise! Other factors like volume and throughput are also important. It would be easy to choose selective robotic coating for all boards, assuming an automation process would be the most cost effective. However, cost of set up and program time against volume need to be considered.
|A good example is where a batch size may only be a monthly drop of 10 boards at a time and it costs more to set up the robot than to coat the board and the speed advantage has been lost. Another point with robotic systems is whether the board design is suitable for selective spray? If the board is very 3D in nature or has areas which are critical as no go for coating then it may be a difficult option and at least some of the process may have to be manual in nature. Finally, factors such as budget are very important. Amortisation of costs other a number of boards gives’ the final cost of the project. It just may be the case that cost of capital equipment cannot be returned easily and lower cost solutions may need to be found such as aerosols or subcontracting the work out.
In the end it is the balance of factors which matters and this is the reason SCH have more than sixty different conformal coatings and a variety of application methods available since there is no perfect way to coat all boards.