Issue link: https://iconnect007.uberflip.com/i/1533085
MARCH 2025 I DESIGN007 MAGAZINE 57 I tell my class that there's no such thing as giv- ing fabricators too much information, but you can handicap the fabricator by specifying cer- tain things. Maybe the designers specify a via. ey want to put a tolerance on it, ±3 mils. But in most situations, via size isn't design criti- cal. I explain that this designer should specify "Plus 3 minus the hole size." at allows the fabricator to take your pad design and select a drill that will help them meet Class 3 or Class 2 standards. I talk to them about cop- per weights and make it clear that when you tell the fabricator a start weight copper, that fab now has to default to IPC for internal and external copper; now the fab has rules to fol- low at that thickness. Dack: If designers start by defining base cop- per based on their performance needs and let IPC-6012 determine the finished thickness for that weight, will they be fine? You don't need to specify base copper. Just tell the fabricator, "is is what my finished cop- per thickness needs to be." Is it half-ounce or 1-ounce copper? If you say, "I need a 1-ounce or half-ounce starting copper," that defines the etch compensation rules for the fabricator. en the designer decides on hole fill; the lay- ers get plated, and the plating gets higher. e team decides they need a little bit more than Class 3 and that's affecting all the rules for the fabricator without even understanding what you're trying to achieve as a designer.