Reliability

Qualification Requirements

The qualification requirements for Pb-free external lead finish differ for surface-mount device (SMD) or through-hole devices (THD).

For the THDs the primary qualification requirement is to demonstrate forward compatibility with new Pb-free solder pastes (based on SnCuAg). The tests to be performed typically include:

• Solderability with SnCuAg solder
• Resistance to Solder Heat

For the SMDs reclassification of the moisture sensitivity level (MSL) at a peak reflow temperature of 260 deg. C is required in addition to solderability validation. The MSL reclassification is performed on the largest die size that is used in the package. The tests to be performed typically include:

• Preconditioned Highly Accelerated Stress Testing (PC-HAST) - 96 hours minimum
• Preconditioned Autoclave (PC-AC) - 96 hours minimum
• Preconditioned Temperature Cycling (PC-TC) - 500 cycles minimum
• (Preconditioning is performed at the target MSL for 260 +5/-0 Deg. C)
• Preconditioning is performed at the target MSL)
• SAT after preconditioning to check for delamination
• Solderability with SnCuAg solder
• Resistance to Solder Heat (RSH - Solder Immersion)

Preconditioning

ON Semiconductor adheres to JEDEC standard J-STD-020C for preconditioning requirements for surface mount packages. The JEDEC methodology utilizes a predefined moisture soak followed by three reflow soldering passes to simulate warehouse storage and a customers two-sided board assembly process plus one repair cycle.

The reflow profile used by ON Semiconductor for Pb-free products is shown below. All profile features meet JEDEC standards. One profile feature, Peak/Classification Temperature (Tp), exceeds JEDEC requirements. At ON Semiconductor, all products are reflowed with a peak temperature of 260°C +5/-0 regardless of package size and volume.

Profile Feature	Sn-Pb Eutectic Assembly	Pb-Free Assembly
Preheat/Soak Temperature Min (Tsmin) Temperature Max (Tsmax) Time (ts) from (Tsmin to Tsmax)	100 °C 150 °C 60-120 seconds	150 °C 200 °C 60-120 seconds
Ramp-up rate (TL to Tp)	3 °C/second max.	3 °C/second max.
Liquidous temperature (TL) Time (tL) maintained above TL	183 °C 60-150 seconds	217 °C 60-150 seconds
Peak package body temperature (Tp)	For users Tp must not exceed the Classification temp in Table 4-1. For suppliers Tp must equal or exceed the Classification temp in Table 4-1.	For users Tp must not exceed the Classification temp in Table 4-2. For suppliers Tp must equal or exceed the Classification temp in Table 4-2.
Time (tp)* within 5 °C of the specified classification temperature (Tc), see Figure 5-1.	20* seconds	30* seconds
Ramp-down rate (Tp to TL)	6 °C/second max.	6 °C/second max.
Time 25 °C to peak temperature	6 minutes max.	8 minutes max.
* Tolerance for peak profile temperature (Tp) is defined as a supplier minimum and a user maximum.

 

Moisture Sensitivity Level (MSL)

Surface Mount Packages are qualified to 260 +5/-0 degrees C which exceeds JEDEC standard J_STD-020C.

The majority of the package MSL ratings will remain unchanged from the current MSL 1 classification. All packages have an MSL rating of MSL3 or better.

If there is a change in the MSL rating of a package, the customer will be notified and appropriate packing precautions will be taken before any product is shipped by ON Semiconductor (such as dry packing).