This month’s article shares a sampling of the baseline appearance related tests Hatch performs on custom Android tablets to ensure the product meet Hatch’s quality standard. Beyond the baseline tests, when checking the quality of a custom Android tablet Hatch will add custom quality checks based on that product’s specific functionality or requirements. If the custom Android device has 2 SD card ports, Hatch will add tests to check their functionality and usability. For example, transferring data between the ports themselves and the tablet’s internal memory and the ease of inserting the SD card into the slot.

The name of each specific check is followed by details of the inspection process.

Cosmetic Defects

These are checks that relate to the appearance of the custom Android tablet. The appearance of a tablet has three classifications based on areas of the product.
Class AA: refers to the active display area. This is the area where the image appears.
Class A: refers to the area which is visible when watching the display within the viewing angle.
Class B: refers to the area which is not visible during watching the display.

Definition: A surface defect is any kind of defect, which changes surface shape or color.

Tolerance

Screen size, in.	Surface class	Defect square, mm²	Qty, pcs	Minimal distance, mm
6…7	AA*	≤0.02	≤1	≥25
	A	≤0.1	≤1	≥25
	B	≤0.2	≤2	≥25
	AA*	≤0.02	≤2	≥25
7.85…8	A	≤0.1	≤2	≥25
	B	≤0.2	≤3	≥25
	AA*	≤0.02	≤3	≥25
9…10.1	A	≤0.1	≤3	≥25
	B	≤0.2	≤4	≥25

* Including Mura defects.

** If distance between defects is lower than allowed, then defects are treated as a parts of one and their squares are to be summed.

Mold Parting Lines

Plastic injection parts are created by forcefully injecting molten plastic inside two steel molds. The two molds are separately milled to create a space for the molten plastic to settle and harden into the part that’s used in casing of the finished product.

Definition: Mold parting line is the convexity of the molded parts along the line of mold core and mold cavity parting.

Tolerance

Height, mm	Width, mm
≤0.1	≤0.1

Print Defects

Custom Android tablets and electronics in general usually have some text or artwork on the case.  Common printing methods include silk screen, embedding in the mold, and laser engraving.  The artwork includes logos, like a brand mark or the logo of a certification (such as FCC, CE, NOM, Anatel, etc).  Text usually appears next to buttons or ports, so the user knows what to use them for, or to display the model name or number.

Definition: Print defects are to be evaluated by such parameters as shift and tilt.

Tolerance

Location	Shift, mm	Tilt, degrees
Brand Logo	≤3	≤1
Certification Logo	≤5	≤1
I/O Ports Names	≤0.5	≤2
Button Names	≤0.5	≤1

Flushness and Gaps

When making a tablet case, whether it’s metal or plastic, there’s always a stage in the process to refine the parts, ensuring they fit together perfectly.  Common issues are the gaps between the parts and ensuring a proper fit between the internal connection points.  Here’s the inspection done to check the appearance of where case parts meet.

Definition: Flushness and gaps are step height and distance between the attendant edges of abutted parts.

Tolerance

Flushness, mm	Gaps, mm
≤0.2	≤0.2

Color/glossiness deviation

Many tablet cases are painted after coming out of their molds.  Sometimes the painting process has flaws which create non-uniform coloration.  Color appearance problems can also happen when color aren’t mixed properly during the case painting or silk screening processes.  Ways to prevent color appearance discrepancies include using specific Pantone colors or another kind of color standard and doing a visual comparison with an approved sample, commonly referred to as the ‘Golden Sample’.

Definition: Color or glossiness deviation is difference of mechanical parts color or glossiness, including artwork, comparatively to the reference.

Tolerance

Reference	CIE76 ∆E	∆G, GU
Itself (uniformity)	≤2	≤5
Golden sample*	≤4	≤10

*Sample signed by counterparts before mass production.