A. Simply stated, it stands for Solder Mask Over Bare Copper. Traditional solder mask coatings are done over a reflowed tin/lead finish. Although the tin/lead finish is desirable for the pads for better solderability, this tin/lead coating is not necessary for the rest of the circuitry if it is protected by solder mask. The real reason for developing this process was to prevent the wrinkling effect of the tin/lead trapped under the solder mask when it is again reflowed during the assembly operation when the components are soldered with a wave solder machine.
02) How can I save money when I create a new design?
02) How can I save money when I create a new design?
A. It's called DFM - Design for manufacturability. This consideration in designing the artwork will save money over and over again during the manufacturer of the bare boards and the assembly of these boards. Contact us for detail.
03) Can you perform an electrical test on our boards and if so, how is this done?
03) Can you perform an electrical test on our boards and if so, how is this done?
A. We prefer to test your boards but this is an optional process requiring a test fixture charge. You will not pay for this fixture again if the board does not change. The test is a bed of nails netlist test for opens and shorts based on the nets extracted from the Gerber files supplied for the fabrication. Once tested, the boards have been verified to match the Gerber files 100% against opens or shorts.
04) What is the most efficient method of providing a PCB manufacturer with artwork?
04) What is the most efficient method of providing a PCB manufacturer with artwork?
Most companies have moved away from hard copy artwork these days. The generally accepted method is to transfer electronic (Gerber and HPGL) data by modem or Internet. However modems can sometimes be troublesome with compatibility problems, busy lines and the expense of long distance calls. So increasingly the Internet offers a trouble free, cost effective service. An important point, most PCB manufacturers prefer customers to include the machining details in the form of a drawing within the electronic data package. This enables work to begin immediately - often this item is forgotten.
05) What is the best way to dimension the finished profile of the board?
05) What is the best way to dimension the finished profile of the board?
The profile of a board should always be referenced to an easily recognized datum. This can either be a component hole or the finger of a gold edge connector. Clear, uncluttered dimensions eliminate any chance of error or confusion. The golden rule must be keep it clear and simple.
06) How much space do I have for silk screen legend?
06) How much space do I have for silk screen legend?
All the area not occupied by drilled holes or surface mount pads. It is often difficult to design a board that meets this requirement. When designs are received where silk screen legend encroaches upon the holes or pads a competent manufacturer will have the facility in its front end work stations to clip out the offending text. This obviously needs the customer's permission and can delay the commencement of production.
07) What is the practical limit for solder mask dams between surface mount pads?
07) What is the practical limit for solder mask dams between surface mount pads?
This should be considered as 0.1 mm for the production of cost effective boards.
08) Do via holes need pads on the outer layers?
08) Do via holes need pads on the outer layers?
Yes, and it should be remembered that these must be at least 0.3mm larger than the finished hole size to ensure that the drilled hole is adequately surrounded by copper at all stages of manufacture.
09) Can I leave isolated tracks on the surface of the board?
09) Can I leave isolated tracks on the surface of the board?
This is a most unwise procedure. These isolated tracks will become over plated and will be difficult to cover with solder mask. If the design needs an isolated track then it is advisable to cross hatch the unpopulated area.
10) What is the smallest via hole that can be incorporated before incurring additional cost?
10) What is the smallest via hole that can be incorporated before incurring additional cost?
As boards are stacked for drilling, the size of the smallest hole determines the drilling stack height. Often via holes are unnecessarily made too small with the effect of increasing drilling costs. For most manufacturers, the smallest via before incurring a cost penalty would be around 0.45mm finished size.
11) What are the cost implications of buried vias?
11) What are the cost implications of buried vias?
The cost of a blind and buried via board depends upon the quantity of holes between different layers as this will dictate the number of bonding and drilling operations. Typically a 50% increase in price occurs. It is often more cost effective to increase the layer count by 2 layers than move to blind and buried via.
12) How can I differentiate between development and production boards?
12) How can I differentiate between development and production boards?
One method is to use a different color resist to the standard green. In particular, boards with red resist are very easy to spot. An alternative method is to print legends with a different silk screen color, white or yellow being standard.
13) What format can you read?
13) What format can you read?
We prefer to receive Gerber data, HPGL, extended Gerber CAM350 (RS274X) or ACAD DWG/DXF, but if you cannot output in these formats, send your design data and we will arrange for it to be post processed.