IPC Printed Circuit Board Requirements

IPC classifications describe industry-set standards of quality in PCB design, manufacturing and assembly. PCBI manufactures a minimum of IPC Class 2 PCBs and can satisfy requirements for class III manufacturing. Class 2 includes most industrial products and consumer electronics that require longer life cycles, while still allowing for minor cosmetic imperfections that do not compromise mechanical or electrical functionality. Class 2 is the most common choice in PCB fabrication and has the most balance in terms of cost and performance expectations.

Class 3 manufacturing comes at a premium cost for good reason. Products falling into this category require longer operational life cycles, on-demand performance, high-reliability and have the most controlled manufacturing tolerances and specifications of all three classes. Aesthetic defects that do not affect electrical or mechanical functionality that can meet Class 2 standards would fail inspection for Class 3. You'll find Class 3 PCB in industries such as flight, high-end medical equipment and automotive. Multiple testing and inspection points throughout the manufacturing process drive up the cost in addition to slowing down production. The number of through-hole technology used in your design can also considerably slow the manufacturing process as Class 3 requires the vertical fill of the barrel at 75% (compared to 50% for Class 2). Consider longer lead times if Class 3 requirements are necessary for your project.

The chart below breaks down the specific requirements to meet each standard. Contact us to learn more.

Common IPC-6012D/DS Requirement Differences Per Product Class

Characteristic		Class 2	Class 3	Class 3A*	IPC 6012D/DS RequirementUOS**
Annular Ring External PTH		90° Breakout Accepted Line width to meet Req.	50 μm [0.00197 in.] min. 20%isolated area reductions due to	50 μm [0.00197 in.] min. 20% isolated area reductions due todefects permitted. Tear Drops AABUS	Table 3-9 / 3.4.2
Annular Ring Internal PTH		90° Breakout Accepted Line width to meet Req.	25 μm [0.00098 in.] min.	25 μm [0.00098 in.] min.	Table 3-9 / 3.6.2.1
Annular Ring, Unsupported Hole		90° Breakout Accepted Line width to meet Req.	150 μm [0.00591 in.] min.	150 μm [0.00591 in.] min.	Table 3-9 / 3.2.4
Burrs and Nodules		Accepted if minimum hole diameter and copper thickness is met			Table 3-10
Bow & Twist		Max. of 0.75% for Surface Mount Boards / 1.5% for all others			3.4.3
Cracks, Laminate		Cracks within and outside not > 80 μm [0.00315 in]			3.6.2.4
Cracks, Barrel / Corner		None Allowed			Table 3-10
Cracks, External Foil		Allowed if not extended into plating			Table 3-10
Cracks, Internal Foil		None Allowed			Table 3-10
Dielectric Thickness/Spacing		90 μm [0.00354 in.] min. unless specified			3.6.2.17
Lifted land (Visual)		None allowed on the delivered (non-stressed) printed board			3.6.2.10
De-wetting Solder Connection areas		5% Max	5% Max	None allowed*	3.5.4.5
De-wetting Solder Connection areas		Conductors and planes are permitted
Plating Thickness, Copper, Through, Blind, Buried Vias, >2 Layers, Average		20 μm [0.00079 in.] min.	25 μm [0.00098 in.] min.	25 μm [0.00098 in.] min.	3.6.2.11 Table 3-4
Plating Thickness, Copper, Through, Blind, Buried Vias, >2 Layers, Thin Areas		18 μm [0.00071 in.] min.	20 μm [0.00079 in.] min.	25 μm [0.00098 in.] min.*	3.6.2.11 Table 3-4
Plating Thickness, Copper, Through, Blind, Buried Vias, >2 Layers, Wrap		5 μm [0.00019 in.]	12 μm [0.00047 in.]	12 μm [0.00047 in.]	3.6.2.11 Table 3-4
Plating Thickness, Copper, Blind and Buried Microvias, Average		12 μm [0.00047 in.] min.	12 μm [0.00047 in.] min.	20 μm [0.00079 in.] min.*	3.6.2.11 Table 3-5
Plating Thickness, Copper, Blind and Buried Microvias, Thin Areas		10 μm [0.00039 in.] min.	10 μm [0.00039 in.] min.	18 μm [0.00071 in.] min.*	3.6.2.11 Table 3-5
Plating Thickness, Copper, Blind and Buried Microvias, Wrap		5 μm [0.00019 in.]	6 μm [0.00024 in.]	6 μm [0.00024 in.]	3.6.2.11 Table 3-5
Plating Thickness, Copper, Buried Via Cores (2 Layers), Average		15 μm [0.00059 in.] min.	15 μm [0.00059 in.] min.	20 μm [0.00079 in.] min.*	3.6.2.11 Table 3-6
Plating Thickness, Copper, Buried Via Cores (2 Layers), Thin Areas		13 μm [0.00051 in.] min.	13 μm [0.00051 in.] min.	18 μm [0.00071 in.] min.*	3.6.2.11 Table 3-6
Plating Thickness, Copper, Buried Via Cores (2 Layers), Wrap		5 μm [0.00019 in.]	7 μm [0.00027 in.]	7 μm [0.00027 in.]	3.6.2.11 Table 3-6
Nicks and Pinholes, Planes		Max. size is 1.0 mm [0.0394 in] with not more than 4 per side, per 625 sqcm [96.88 sqin]			3.5.4.1
Negative Etchback		25 μm [0.00098 in.]	13 μm [0.00051 in.]	None allowed*	3.6.2.8
Positive Etchback		Between 5 μm [0.000197 in.] and 80 μm [0.00315 in.] with preferred depth 13 μm [0.000512 in.]		Between 5 μm [0.000197 in.] and 40 μm [0.001574 in.] with preferred depth 13 μm [0.000512 in.]*	3.6.2.6
		The combination of dielectric removal from etchback plus wicking allowance shall not exceed the sum of the maximum allowable etchback or smear removal and the maximum allowable wicking limits in *Table 3-10 and as depicted in Figure 3-15.
Surface Mount Lands		Defects along edge of land not > 20%; internal defects not > 10%			3.5.4.2.1
		Defects internal to the land remain outside central 80% of the diameter.
Plating Separation		None Allowed			Table 3-10
Voids, Laminate		Voids within and outside thermal zone not > 80 μm [0.00315 in.]			3.6.2.3
Voids, Copper in Holes (Visual)		One per hole in not more than 5% of the holes	None allowed	None allowed at 3 diopters (approx. 1.75X)*	3.3.3 Table 3-7
Voids, Final Finish Plating (Visual)		Three per hole in not more than 5% the holes	One per hole in not more than 5% of the holes	None allowed at 3 diopters (approx. 1.75X)*	3.3.3 Table 3-7
Nail Heading		Acceptable - indicator of process variation - alert management			3.6.2.19
Inner layer Inclusions/Separations		None Allowed			Table 3-10
Cap Plating of Filled Holes (Visual)		When cap plating of the filled holes is specified on the procurement documentation, plating voids exposing resin are not allowed, unless covered by solder mask. Must maintain structural integrity.			3.5.4.8
Cap Plating of Filled Holes Min.		5 μm [0.00019 in.]	12 μm [0.00047 in.]	12 μm [0.00047 in.]	3.6.2.11.2 Table 3-11
Cap Plating of Filled Holes Depression – max.		127 μm [0.005 in.]	76 μm [0.0030 in.]	76 μm [0.0030 in.] general areas 50 μm [0.0020 in.] in BGA areas	3.6.2.11.2 Table 3-11
Cap Plating of Filled Holes Protrusion – max.		50 μm [0.0020 in.]	50 μm [0.0020 in.]	50 μm [0.0020 in.]	3.6.2.11.2 Table 3-11
Electrodeposited Copper Tensile Strength		> 248 Mpa [36,000 PSI]	> 248 Mpa [36,000 PSI]	> 275.8 Mpa [40,000 PSI]	3.2.6.2 per IPC-TM-650 2.4.18.1
Electrodeposited Copper Elongation		> 12%	> 12%	> 18%	3.2.6.2 per IPC-TM-650 2.4.18.1
*Requirements for Class 3A product are referenced in IPC-6012DS.				**UOS = Unless Otherwise Stated
IPC 6012 Class Chart.doc	For Reference Only			Rev:13-Oct17

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IPC REQUIREMENT DIFFERENCES

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