SURFACE MOUNT TECHNOLOGY (SMT)<br>LEADLESS CHIP CARRIERS "LLCC"

SURFACE MOUNT TECHNOLOGY (SMT) LEADLESS CHIP CARRIERS "LLCC"
	LEADLESS CHIP CARRIERS Leadless Chip Carriers (LLCC) packages are characterized by external connections consisting of metallized inset terminations (a castellation), making the package resemble a miniature castle. The use of LLCC packages is not recommeneded for high reliability/spaceflight applications, due to the limited mechanical reliability of the terminations. See Section 7.01 "Surface Mount Soldering, General Requirements", for common accept/reject criteria.

PREFERRED The part is centered with the castellations centered across the width of the land pattern area and properly oriented. Solder fillets exhibit complete wetting, proper thickness and positive angle. NASA-STD-8739.2 [12.8.1], [12.9.7.a]	ACCEPTABLE The part is not centered, but the castellations are on the land pattern (there is no side overhang). NASA-STD-8739.2 [12.8.1], [12.9.7.a]

ACCEPTABLE END JOINT WIDTH (C) The width of the solder joint shall be equal to the castellation width (W). NASA-STD-8739.2 [12.8.1], [12.9.7.a]	ACCEPTABLE MAXIMUM FILLET HEIGHT (E) The fillet shall extend to the edge of the castellation metallization, and shall have a positive wetting angle. NASA-STD-8739.2 [12.8.1], [12.9.7.a]

SURFACE MOUNT TECHNOLOGY LEADLESS CHIP CARRIERS "LLCC"(cont.)

ACCEPTABLE MINIMUM FILLET HEIGHT (F) The solder fillet shall extend upwards at least 75% fo the castellation metallization, and shall have a positive wetting angle. NASA-STD-8739.2 [12.9.7.b.2]	ACCEPTABLE SIDE JOINT LENGTH (D) The length of the side joint(D) shall be 50% of the minimum fillet height (F), or the land length external to the package (S), whichever is less. NASA-STD-8739.2 [12.9.7.a]

ACCEPTABLE SOLDER FILLET The solder fillet may have a bulbous appearance, but shall be well-wetted and exhibit a positive angle at the castellation and pad terminus. NASA-STD-8739.2 [12.9.7.a]	UNACCEPTABLE EXCESS SOLDER The solder fillet shall not exhibt a negative wetting angle at the top of the termination and/or at the edge of the land area. NASA-STD-8739.2 [12.9.7.b.3]

ACCEPTABLE SOLDER THICKNESS (G) The solder thickness shall elevate the chip body by at least 0.127 mm (0.005 in.) above the printed wiring board surface, unless satisfactory cleaning can be demonstrated with reduced clearance. NASA-STD-8739.2 [12.9.7.a.3]	UNACCEPTABLE INADEQUATE SOLDER THICKNESS (G) A spacing of less than 0.127 mm (0.005 in.) between the chip body and the printed wiring board surface may prevent removal of flux and solder fines from underneath the chip NASA-STD-8739.2 [12.9.7.a.3]

SURFACE MOUNT TECHNOLOGY (SMT) LEADLESS CHIP CARRIERS "LLCC"(cont.)

UNACCEPTABLE END OVERHANG (B) End overhang of the edge of the chip body (with respect to the pad termination end) is not permitted. NASA-STD-8739.2 [12.6.2.9]	UNACCEPTABLE IMPROPER WETTING The solder fillet shall exhibit a positive wetting angle, wet all elements of the connection, and shall extend to the edge of the pad. NASA-STD-8739.2 [12.9.7.a.1]

UNACCEPTABLE INSUFFICIENT SOLDER The minimum fillet height (F) shall not be less than 75% of the castellation thickness. NASA-STD-8739.2 [12.8.2.b.6], [12.9.7.b.2]	UNACCEPTABLE NONWETTING The fillet shall not exhibit non-wetting at the top of the solder fillet. NASA-STD-8739.2 [12.9.7.b.4]

UNACCEPTABLE POOR FLOW The fillet shall not exhibit poor or uneven flow at the top of the solder fillet. NASA-STD-8739.2 [12.9.7.b.4]	UNACCEPTABLE SIDE OVERHANG (A) The castellation shall not overhang the edge of the land. NASA-STD-8739.2 [12.9.7.b.1]


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