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Page 48 of 109

JULY 2019 I PCB007 MAGAZINE 49 Product specification begins at the time of quote and is continuously updated through dialogue with the customer until production begins. Our experience at NCAB shows that about 30% of all of the new articles provided to us arrive with missing data or contain am- biguous or conflicting information in describ- ing the build. This causes engineering ques- tions (EQs) to be raised, which take time to clarify and can easily affect delivery dates. Some examples of missing, ambiguous, and conflicting information include: • Outline information/data/drawings • Unspecified plated or non-plated holes • Unspecified surface finish • Unspecified copper thickness • Unspecified material to be used • Unspecified color of solder mask/legend print • Unspecified thickness of the finished board • Missing Gerber or drill files • Board thickness does not match the specified build • Legend print included in the documentation but not to be printed • Dimensions on the drawing do not match the Gerber outline • Number of holes in drill drawing does not match with the number of holes detailed in the supplied drill file • The hole sizes in the drill drawing do not match the sizes in the drill file • Copper thickness in specification is not per IPC • Specified impedance requirements cannot be achieved based upon the stated build • Attached netlist contains short/opens compared to Gerber files Recommendations So, how does a design team avoid these data transfer pitfalls? Here are five key recommen- dations for preparing to transfer a design to manufacturing. 1. Include the Original Data And if this is a move, include the working files. Providing both sets of data ensures your design matches what you should have already been receiving and reduces the number of EQs. Tooled data is very useful when delivered along- side the original files. If this is a first-time build, it helps to provide the desired array layout, en- suring the supplier produces the correct array. 2. Include Stackups Another factor that will greatly increase the likelihood of a correct build includes stackups (previous or desired). Not specifying the stack- up could yield a different end-result depend- ing on manufacturer preferences and materi- al choices, affecting designed impedance and other performance issues. 3. Include Any Previous EQs Assuming the order has previously received pre-production engineering, it's helpful to in- clude documentation on any previous EQs. Those previously answered questions will help reduce repeat questions. Some common exam- ples of items that might trigger an EQ include: • Unterminated traces • Shorts (intentional or unintentional) • Conflicting information in the fabrication documentation If this is a first-time build, expect to receive EQs. A good supplier will ask detailed ques- tions before building anything. If you do not receive questions, you should be suspicious of what that supplier changed without consent.

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