Large boards and pooling – new guidelines
|425×425 top view|
Over the last 12 months we have received an increasing number of boards in our pooling services at the maximum size allowed 425 x 425 mm. These are not genuine single circuits but panels made up of many smaller circuits. To get around our specified maximum panel size 350 x 250 mm, the individual circuits on these oversize panels are not profiled out. In that way the users can describe the panel as a single circuit, though we know, of course, that they will subsequently cut out the individual circuits.
This practice raises two serious issues.
First it impacts on the overall efficiency of the pooling service.
To keep prices down for all our customers we need to use as much of each pooling panel as possible. The more customers’ orders we can produce for a given area of material, the lower can we make our prices. But a panel 425 x 425 mm means that the rest of the pooling panel is wasted. That’s one reason why we set the maximum customer panel size at 350 x 250 mm (the other is that this is also the largest standard size panel used on many or most automatic assembly machines). We allowed a maximum circuit dimension of 425 mm to give maximum flexibility to our customers, knowing that very few actually need individual circuits 425 x 425 mm.
Second, it is likely to produce less good PCBs.
Putting together panels with several different circuits on them requires skill and experience to optimise tooling and to achieve a good copper balance on each side and side to side. We use sophisticated software to calculate the plating index which measures how well the copper is balanced. When we apply this to these large combination panels, in most cases we see a very poor copper balance with significant areas of over- and under-plating, reducing the quality of the finished circuits.
|425×425 bottom plating||425×425 top plating2||425×425 bottom plating 2||425×425 top plating|
To avoid these issues we have decided to set the maximum size of a single circuit on our pooling services at 8.75 dm2, the same area as our largest eC-registration-compatible panel 350 x 250 mm. You can order larger boards up to a maximum in one dimension of 425 mm, (e.g. 425 x 100 mm) so long as the total area is not more than 8.75 dm2.The largest panel size on the pooling services remains 350 x 250 mm whether panelised by Eurocircuits or by the customer. Further it is our policy that all customer panels prepared by us according to the Eurocircuits panel rules are eC-registration-compatible (maximum 350 x 250 mm to fit the eC-equipment).
If you need a single circuit larger than 8.75 dm2 or a panel larger than 350 x 250 mm, then upload it as an inquiry in On demand. We will check that it is falls within the parameters of good production practice. If it does, we will send you a quotation. If not, we will make suggestions to improve its manufacturability.