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Conformal LGA PTH structure having Via In Pad , partial hard Ni /Au , Copper opposite to LGA side-- CITC performance of robust structure & Use thereof

IP.com Disclosure Number: IPCOM000016285D
Original Publication Date: 2002-Oct-04
Included in the Prior Art Database: 2003-Jun-21
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Abstract

Conformal LGA PTH structure having Via In Pad , partial hard Ni /Au , Copper opposite to LGA side-- CITC performance of robust structure Use thereof Copper thickness on Plated thru hole (PTH) is very critical. Current induced thermal Cycling (CITC) data suggest that PTH reliability exposure exists when there is less than 0.7 mil copper thickness is present . Such PTHs , bearing galvanic etch potential conditions, upon thermal exposure cracks (see below). fails CITC below 10 cycles. Higher the copper thickness better the CITC performance.

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  Conformal LGA PTH structure having Via In Pad , partial hard Ni /Au , Copper opposite to LGA side-- CITC performance of robust structure & Use thereof

Copper thickness on Plated thru hole (PTH) is very critical. Current induced thermal Cycling (CITC) data suggest that PTH reliability exposure exists when there is less than 0.7 mil copper thickness is present . Such PTHs , bearing galvanic etch potential conditions, upon thermal exposure cracks (see below). & fails CITC below 10 cycles. Higher the copper thickness better the CITC performance.

CITC DATA :

1

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Cycles to Fail vs Cu Plating thickness in Partial Ni/Au PTH

1000

10 and 14mil drilled via in 120mil thick board

10mil drilled PTH EOL 14mil drilled PTH EOL

Preferred range for Reliable PTH:

Cu Plate >= 0.9 (as plated)

Cu Plate >= 0.7 (EOL before assembly)

CITC cycles > 10

PTH Reliability Exposure

CITC "Reflow" Cycles to Fail

100

10

1

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

Copper Thickness in PTH (mils)

2

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