In 2011, the value of Gold (Au) surged to $1900/ozwhich had a drastic influence on Wirebonded ICs utilizing Au wires. IC suppliers scrambled to transform from Au to copper (Cu) wire on as many merchandise as they might. Nevertheless, automotive ICs have been reluctant to make the bounce because of lack of reliability information and efficiency track-record. Nevertheless, in the present day’s automotive ICs are huge customers of Cu wires pushed by value and reliability concerns.

In 2021, the automotive semi market was $52.6B and it has grown 5x since 2001 (Supply: Omdia). Wirebond ICs are the dominant a part of this rising market in the present day. Wirebond packaging represents greater than 90% of the automotive packaging market (Supply: Yole).

Previous automotive ICs proceed to make use of Au wire, however new wirebond ICs are nearly all the time designed with Cu wires. Aside from excessive value, Au wires additionally present reliability points after Excessive Temp Storage Life Testing (HTSL). Particularly, Kirkendall voids are noticed within the joint between the wire and the Aluminum pad. Cu wires don’t present such voids as seen within the following determine.


Supply: Yole Developpement Automotive Packaging Markets and Know-how Traits Report 2019

Previous automotive ICs proceed to make use of Au wire, however new wirebond ICs are nearly all the time designed with Cu wires. Aside from excessive value, Au wires additionally present reliability points after Excessive Temp Storage Life Testing (HTSL). Particularly, Kirkendall voids are noticed within the joint between the wire and the Aluminum pad. Cu wires don’t present such voids as seen within the following determine.


HTSL 1000h @ 175C Outcomes

For brand spanking new functions, Cu wires have grow to be the default because of decrease value, higher conductivity, HTSL efficiency, and now mature gear/course of capabilities. Nevertheless, Cu wires do pose some challenges:

    1. Cu wire is tougher than Au wire and the die bond pad construction should be evaluated for compatibility with the upper stress related to Cu wirebonds. The presence of lively circuitry underneath the bond pads may be in danger to be used with Cu wires. This is without doubt one of the most important causes that many older gadgets utilizing Au wires couldn’t be retrofitted with Cu wires. Even with suitable gadgets, materials and course of controls are obligatory to guard towards pad injury.
    2. Though Cu wire reveals comparatively higher HTSL & Temperature Biking (TC) efficiency, it’s extra prone to HAST (Extremely Accelerated Stress Take a look at) reliability failures. The presence of Chlorine (Cl) ions within the Epoxy Mould Compound (EMC) results in Intermetallic Compound (IMC) corrosion that may trigger an open joint failure. Different points of the EMC similar to PH stage and Sulfur content material should be additionally thought-about.
    3. Cleaner meeting surroundings is necessary to eradicate contaminants that may result in reliability failures with Cu wires. This requires tighter controls and surroundings monitoring to cut back contaminant particle counts and their attainable sources.
    4. Different BOM parts similar to leadframe/substrates, die connect and the particular variation of Cu wire chosen are necessary. There are several types of Cu wires.

a.  Probably the most widespread Cu wires is the AuPCC (Gold and Palladium Coated Copper Wire). This wire has a 4N Cu (4 “Nines” = 99.99% purity) core with a Pd coating and Au coating.
b.  Two different variations are additionally getting used for greater reliability:

i.   Alloyed Cu wire makes use of 2N Cu (99% purity) doped with different supplies. The objective is to realize improved Excessive Temp Storage Life efficiency.
ii.  Hybrid Cu wire is much like Au PCC wire however makes use of a 2N Cu core doped with different supplies. That is supposed to realize superior efficiency in automotive reliability testing. The Hybrid Cu wire additionally has higher workability in contrast with Alloyed Cu.

The Automotive Electronics Council (AEC) has launched a reliability spec referred to as AEC-Q006 that should be used with AEC-Q100/101 to qualify automotive ICs utilizing Cu wires. This spec outlines stringent reliability standards to make sure that Cu wire ICs can carry out reliably in an automotive surroundings. To realize this reliability, cautious materials choice and course of optimization are obligatory. Cu wire is now the wire of selection in all wirebond functions and its use will solely develop in automotive functions sooner or later.

Prasad Dhond

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Prasad Dhond is Vice President of Amkor’s Wirebond BGA Merchandise. He beforehand led the Automotive market section and managed the Quad and Twin Leadframe product strains. Previous to becoming a member of Amkor in 2014, Dhond labored at Texas Devices for 12 years the place he held roles in product definition and advertising within the Analog product group. He holds a BSEE diploma from The College of Texas at Austin and an MBA from the Southern Methodist College.



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