Lead-free is defined as the non-intentional use of lead (Chemical symbol Pb) and less than 1000ppm in a homogeneous material. In an IC package, Pb is commonly found in the external lead finish or plating. In Chip Scale Packages (µCSP)/Wafer Level Packaging (WLP) and FlipChip, Pb may be found in the solder bumps.

Lead-free (Pb-free) surface finishes on most leadframe based packages are commonly composed of 100% matte tin (followed by annealing for 1 hour at 150°C). The exception is a few leadframe based packages of other EU RoHS-compliant plating finishes such as nickel/palladium/gold. Ball Grid Array (BGA), µCSP/WLP/flip-chip packages usually contain balls or bumps of tin/silver/copper.

For all lead frame based packages except Power Cap family products with 100% matte tin plating, the plating thickness is 400 - 800 microinches (µ-inch), or 10 to 20 microns. Power Cap products include DS9034xxx series or PCT-1 or PCT+1, PCT-2 or PCT+2, PCT-3 or PCT+3 package codes.

All lead-content products with equivalent lead-free qualified versions will be transitioned to lead-free, except those with technology limitations, such as Ball Grid Array and Flip Chip package formats.

If a customer requires that a package type not qualified as lead-free be manufactured and supplied, a request must be submitted to the Maxim Business Units.

Due to technology limitations, some package types are not currently qualified as lead-free. These include certain Ball Grid Array and Flip Chip package formats.

There will be no major changes in price for lead vs. lead-free packages.

It takes at least 4 weeks to get qualification lots assembled and tested. An additional 10 weeks is required for QA Reliability tests.

No. Revision to the die (product) were not necessary. Only packaging materials were changed as needed to comply with RoHS.

Please see: Lookup Lead-Free/RoHS Products and Content Data. Enter the Maxim part # in the "Part Number" search. The MSL is listed in the "Qualification" summary block.

Lead-free, RoHS-compliant part numbers have a (+) within the package code.

Example:
DICE+
G3255+3
W903B+1

All lead-free, RoHS-compliant products will have the (+) symbol marked on the top package in the area nearest Pin 1 lead, notch or dimple.

Package codes containing the "pound" (#) symbol indicate a RoHS-compliant part which has an exemption for lead.

We meet JEDEC J-STD-020C for most package types as follows:

For most SMD (Surface Mount Devices), our standard qualification is at 260°C peak reflow temperature with 3 reflows. See exceptions below.

260 (-5/+0) degrees Celsius.

NOTE: The reflow profile in the above table is only for qualification and is not meant to specify board assembly profiles. Actual board assembly profiles must be based on the customer's specific board design, solder paste and process, and should not exceed the parameters in the table.

240 (-5/+0) degrees Celsius.

NOTE: The reflow profile in the above Table is only for qualification and is not meant to specify board assembly profiles. Actual board assembly profiles must be based on the customer's specific board design, solder paste and process, and should not exceed the parameters in the table.

Yes there are exceptions due to the materials used in certain package types. These products have special suffixes added to the normal product part number as listed below with their profiles.

1. EDIP ("brick") modules are wave solder only. Peak solder temperature is 260°C. Keep in mind the solder is underneath the PCB.
   
   The EDIP module can be successfully processed through conventional wave-soldering techniques so long as temperature exposure to the lithium energy source does not exceed +85°C. Post-solder cleaning with water washing techniques is acceptable, provided that ultrasonic vibration is not used. Such cleaning can damage the crystal. This means that typical settings of 260°C pot temperature and 5 seconds contact time are acceptable, but the plastic body must not exceed 85°C.
   
   
2. Powercap bases can withstand 260°C not to exceed 30s above 255°C.
   
   Powercap (9034-PC0, 9034-PCX) do not get soldered. Max reflow is N/A.
   
   
3. SIPSTIK do not get soldered. Max reflow is N/A.

Maxim will no longer produce products with lead-content. If a lead-content version is needed, the alternative option is solder dip over lead-free finish under special flow. This request must be submitted to the Maxim Business Unit for approval.

For most lead frame based packages, the material is 85% Sn (tin)/15% Pb (lead) plating on external leads. For BGA and µCSP/WLP packages, the solder balls or bumps contain Tin/Lead combinations. For some specialty packages, certain components within the package contain exemptions for lead (example: Resistor).

Yes.

RoHS Substances:
Substances regulated by EU RoHS:
Lead, cadmium, hexavalent chromium, mercury, PBBs, and PBDEs

Possible RoHS substances in end products: Lead

Possible RoHS substances in packing materials: Cadmium

Components and Substances Contained in most leadframe based Plastic Packages:
Components: Leadframes, die attach, bond wire, molding compound, surface finish (plating), silicon chip.
Substances: Copper, iron, zinc, phosphorus, nickel, magnesium, gold, silver, tin, resin, lead (non Pb-free product), silicon and antimony trioxide and bromine (Sb₂O₃ and Br may be used as flame retardants in some molding compounds).

Components and Substances Contained in most µCSP/WLP packages:
Components: Silicon chips, die coats, UBMs (under bump metals) and solder bumps.
Substances: Silicon chips, resin, aluminum, nickel (V), copper, titanium, nickel, vanadium, tin, silver and lead (Pb is in non Pb-free products).

If the part is EU RoHS compliant then it is China RoHS compliant.

Each Maxim manufacturing, assembly and test facility is ISO 14001 registered. To obtain copies of these documents see this link.

At 260°C and below, the predominant lead-free solder pastes are:
Sn/Ag4.0/Cu.5 217°C (240°C–255°C)
Sn/Ag2.5/Cu.8/Sb.5 216°C (225°C–240°C)
Sn/Ag3.5 221°C (245°C–255°C)
Sn/Cu.75 227°C (250°C–260°C)
Sn/Bi3.0/Ag3.0 213°C (225°C–244°C)

NOTE: This list is a summary of solder paste types commonly used in the industry. Maxim doesn't recommend any usage of these pastes nor guarantees any benefits by using them.

Maxim's lead-free termination parts can be mixed with leaded termination parts and reflowed at a lower temperature (240°C) with proper reflow conditions and compatible solder paste. However, the reliability of Maxim parts with leaded terminations are not guaranteed at higher reflow temperature (above 240°C). Some reference sources show data that define a reduction in solder joint reliability by as much as 33% less than Eutectic solder joints when lead and lead-free metallurgies are mixed.

Element/Alloy Melting point (liquidus):
Pure Lead 327.5°C (621.5°F) 
Pure Tin 232°C (450°F) 
85Sn/15Pb 183°C–205°C (361°F–401°F)
70Sn/30Pb 183°C–193°C (361°F–379°F)
63Sn/37Pb 183°C–193°C (361°F–379°F)
60Sn/40Pb 183°C–190°C (361°F–374°F)

For high speed auto plating lines, MSA based electrolytes are most common. Numerous vendors such as Fidelity, Englehardt, LeaRonal, Isihara, Schlotter and other proprietary and home brews are readily available. For manual/rack/barrel plating lines, sulfuric acid based electrolytes are most common. Even more sources are readily available from numerous vendors such as above and lots of non-proprietary home brew chemistries. These are very inexpensive!

Our "green molding compounds" are the only molding compounds that don't have bromine. Aside from the green molding compounds, all of our other molding compounds contain bromine and antimony. The bromine contained in our "non-green molding compounds" is "elemental bromine" and is used as a flame retardant. Elemental bromine does not meet the definition of a PBB (polybrominated biphenyl) or PBDE (polybrominated diphenyl ether).

The reported weight is based on typical weight for a particular package code. Maxim uses multiple assembly locations to meet our customer's demand and to manage risk. The variations are due to multiple tools such as mold cavities and lead shear in addition to slight variations in the dimensions of the leadframe. Maxim's expectation is the weight variation is within 10%.

The unit weight is the weight of a sampled unit. The substance weights are estimated based on knowledge of content based on experience and % declared in the associated MSDS.

Take the weight of the constituent (i.e., lead) and divide by the unit weight. Multiply the outcome by 1,000,000. For example: the weight of lead in the part is 0.000375 grams and the unit weight is 0.1473 grams, therefore ppm = 0.000375/0.1473 × 1,000,000 = 2546 ppm.

Take the weight of the constituent (i.e., lead) and divide by the unit weight. For example: the weight of lead in the part is 0.000375 grams and the unit weight is 0.1473 grams, therefore % = 0.000375/0.1473 = 0.002546 × 100 = 0.2546%.

Tin whiskers are tested during package qualification at assembly site.

Tests performed are:
Prolonged storage at 85°C/85% RH for 500 hours and 1000 hours. 
Storage under 50°C–55°C for 1, 3, 6, and 12 month interval.

Less than 50 microns in any dimension of whiskers is considered acceptable. Visual inspection is performed under 30X magnification. There is currently no JEDEC/IPC standard for tin whisker testing, inspection and acceptance criteria.

Tin Whiskers are controlled and monitored in assembly by:

Visual inspection at 30X magnification. Frequency of 6X/shift, Sample size = 125 parts. 
Plating bath analysis once a day for Tin, acids and bath organic content.

All package body sizes, assembly materials (mold compound and die attach epoxy), assembly processes (down bond and die coat) and fab processes behave differently in a higher reflow environment (above 240°C). Sufficient reliability data is required from all of these packages and process/fab technologies to assure that product will survive and special packaging requirements are determined to eliminate potential field failures.

Note that package and process qualifications can be extended to other packages and process technologies by similarity.

Recommended Reliability Tests are:

IR or Convection reflow at 260°C peak temperature with preconditioning. 
85/85, HAST, Pressure Pot (Autoclave), High Temperature Storage, DHTL. 
Temperature cycling with IR or convection reflow as precondition. 
Solderability testing with and without aging.

Note that package preconditioning would depend on the Moisture Level rating of the package and materials used in lead-free assembly.

Existing Solderability Standard:

For the Western markets, most companies are using the MIL-STD-883 solderability test at 260°C with steam aging. For the European markets, most companies are using the IEC solderability test at 240°C with steam aging. Steam aging times vary from 4–24 hours with most companies doing 8 hours.

Maxim defines green as halogen-free mold compounds only.