lead-frame plating composition change for legacy ......lead-frame plating composition change for...

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XTP526 (v1.2) November 23, 2020 www.xilinx.com 1

Lead-Frame Plating Composition Change For Legacy Eutectic Products

XTP526 (v1.2) November 23, 2020 FAQ: Implications of XCN18024

Overview To ensure business continuity and enable high-volume supply-chain capability for all tin-lead (Sn/Pb) plating type products, Xilinx is qualifying Pre-Plated Lead-Frame (PPF) without solder plating process for QFP packages. The PPF lead-frame will replace the external terminal Sn/Pb lead finish on Sn/Pb QFP packages. This additional lead-frame type will adhere to the same performance, quality and reliability specifications that apply to all product families, proven through extensive qualification and testing. As a result, there is no change in form, fit, function, or reliability with this lead-frame addition.

FAQs Q1: What is the PPF lead-frame? There are certain types of lead-frame widely used in the industry that have multiple layers of material plated onto the lead-frame such as pre-plated lead-frames (PPF). A three-layer lead-frame plating scheme comprising of nickel (Ni), palladium (Pd) and gold (Au) has been widely adopted in the market for over ten years as a green solution for semiconductor packaging (refer to Figure 1). These three-layers are pre-plated onto the lead-frame at the lead-frame supplier before package assembly. The PPF plating will be the external terminal lead finish on the QFP product packages affected. Figure 1: The IC terminal plating for Ag and PPF Lead-Frame (L/F).

Q2: Why is Xilinx making this change? Xilinx assembly supplier will stop Sn/Pb solder planting process in devices from date code DC2001. Therefore, Xilinx has changed the lead-frame from Ag L/F plating to PPF. This change ensures business continuity and enables high-volume supply-chain capabilities while the PPF can meet the restriction of hazardous substances in electrical and electronic equipment (RoHS) directive specification. Q3: When will this change take effect? This change will take effect in devices from date code DC2001.

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FAQ: Lead Frame Plating Composition Change For Legacy Eutectic Products

XTP526 (v1.2) November 23, 2020 www.xilinx.com

Q4: Which products are affected? This change affects all speeds and temperature grades for commercial / industrial “XC” device packages as defined in the tables below (Table 1, Table 2, Table 3). Any associated specification control document (SCD) versions of the standard part numbers are also affected. Table 1: Spartan-II and Spartan-3 FPGA QFP Device-Packages Affected

Device Package-Pin Device Package-Pin Device Package-Pin

XC2S100 PQ208

XC3S100E TQ144

XC3S400 PQ208

TQ144 VQ100 TQ144

XC2S15 TQ144

XC3S200

PQ208

XC3S50

PQ208

VQ100 TQ144 TQ144

XC2S150 PQ208 VQ100 VQ100

XC2S200 PQ208 XC3S200A VQ100 XC3S500E PQ208

XC2S30 TQ144

XC3S250E

VQ100 XC3S50A

TQ144 VQ100 PQ208 VQ100

XC2S50 PQ208 TQ144 XC3S50AN TQ144 TQ144

Table 2: CoolRunner-II CPLD QFP Device-Packages Affected

Device Package-Pin Device Package-Pin Device Package-Pin

XC2C128 TQ144

XC95144XL TQ100 XCR3032XL VQ44

VQ100 TQ144 XCR3064XL

VQ100

XC2C256

PQ208 XC95288XL

PQ208 VQ44

TQ144 TQ144 XCR3128XL

TQ144

VQ100 XC9536XL

VQ44 VQ100

XC2C32A VQ44 VQ64 XCR3256XL

PQ208

XC2C384 PQ208

XC9572XL

TQ100 TQ144

TQ144 VQ44 XCR3384XL

PQ208

XC2C512 PQ208 VQ64 TQ144

XC2C64A VQ100 XCR3512XL PQ208

VQ44

Table 3: QPro PROM QFP Device-Package Affected

Device Package-Pin

XQ17V16 VQ44




Q5: What is the different between the SnPb and PPF finish? There is no difference between the SnPb and PPF lead finish in the SMT process (comparison result found in Table 4). Table 5 shows typical conditions for the solder reflow processing of PPF lead finish. The optimal reflow profile used must take into account the solder paste/flux used, the size of the board, the density of components on the board and the mix between large and small components on the board. For PPF lead finish to avoid de-wetting and non-wetting, the reflow profile used should completely dissolve the Palladium into the solder, so that the solder joint forms with the underlying Nickel layer. The Pre Heat and Peak temperature parameters are advisable to be checked if non-wet and de-wetting is seen per industry guidance. See Table 6 for the X-Section of a PPF lead finish solder joint. For the component appearance, there is no difference for both L/Fs, except the PPF lead terminations will appear as a darker color compared to the SnPb lead terminations which will appear slivery-white. (Refer to Figure 2 and Figure 3). Table 4: SMT comparison for Ag planting and PPF L/F.

Table 5: SMT reflow suggestion profile. Sn63/Pb37 Name JEDEC JSTD-020 Recommendations Profile Parameters Used Max Rising Slope (Ramp Up) Tsmax 3°C/sec. max. < 3℃/sec Max Falling Slope Ramp-down 6°C/sec. max. < 3℃/sec Preheat/Soak Time ts 60-120 sec. at 100~150℃ 50-70 sec. at 150-170C

Melting/Liquidous Time/ (TL:Over 183℃)

tL 60-150 sec. 60~90 sec

Peak Temperature (package body) Tp 235C°C max. for Package Thickness <2.5 mm & Volume <350 mm³ 220°C max for Package Thickness ≥2.5 mm and Volume ≥350 mm³

220°C (package body)

Sn96.5/Ag3.0/Cu0.5 Name Set Max Rising Slope Tsmax 3°C/sec. max. < 3℃/sec Max Falling Slope Ramp-down 6°C/sec. max. < 3℃/sec Preheat/Soak Time ts 60-120 sec at 150-200°C 60~120 sec at 150-180°C Melting/Liquidous Time (TL:Over 217℃) tL 60-150 sec. 60~90 sec Peak Temperature (packagte body) Tp 245-260°C (package size dependent, refer to

JSTD-020 Table 4-2) 245℃




Figure 2: The appearance for original and PPF lead finish.

Figure 3: The lead stand-off of appearance lead.

Original (with solder plating) PPF (Without solder plating)

Figure 4: PPF Lead Finish Solder Joint: Palladium has dissolved into the solder.




Q6: How to check if the solder fillet is acceptable after surface mount? Based from IPC-A-610 “Acceptability of Electronic Assemblies” spec 8.2.5 Flat Ribbon, L and Gull Wing Leads definition, we can observe solder fillet performance. (Refer to Table 6 and Figure 5). Table 6: Dimensional Criteria - Flat Ribbon, L and Gull Wing Leads

Feature Dimension Class 1 Class 2 Maximum Side Overhang A 50% (W) or 0.5 mm (0.02 in), whichever is less; Note 1

Maximum Toe Overhang

B Note 1

Minimum End Joint Width

C 50% (W)

Minimum Side Joint Length

when (L) is ≥3 W D

(1W) or 0.5 mm (0.02 in),

whichever is less

3 (W) or 75% (L), whichever is longer

when (L) is < 3W 100% (L)

Maximum Heel Fillet Height

E Note 4

Minimum Heel Fillet Height

F Note 3 G + 50% (T); Note 5

Solder Thickness G Note 3 Formed Foot

Length L Note 2

Lead Thickness T Note 2 Lead Width Note 2

Note 1. Does not violate minimum electrical clearance. Note 2. Unspecified dimension, or variable in size as determined by design. Note 3. Wetting is evident. Note 4. See 8.2.5.5 Flat Ribbon, L, and Gull Wing Leads, Maximum Heel Fillet Height (E). Note 5. In the case of a toe-down lead configuration, the minimum heel fillet height (F) extends at least to the mid-point of the outside lead bend Figure 5: Target - Class 1 & 2 Fillet Appearances

Acceptable - Class 1 Acceptable - Class 2

A wetted fillet is evident.

Minimum heel fillet height (F) is equal to solder thickness (G) plus 50% lead thickness (T) at connection side.




Q7: What solderability testing is performed on the PPF lead finish? Industry solderability testing follows JEDEC J-STD-002D and consists of either Dip and Look Test or Surface Mount Process Simulation Test. Dip and Look Test: The Dip and Look solderability test per Figure 6 is not recommended to be used on PPF lead finish units as it has been found to give false de-wet and non-wet failures. This is because the Palladium in the PPF must dissolve into the solder allowing the solder joint to be made to the underlying Nickel. With process variations in the Dip and Look including low solder temperature or immersion time, the Palladium will often not completely dissolve in the solder and de-wet and non-wet failures will result. Figure 6: Dip and Look Solderability Testing

Surface Mount Process Simulation Test: This method per Figure 7 is recommended for the solderability testing of PPF lead finish units. Figure 7: Surface Mount Solderability Testing

The steps for the surface mount solderability test are as follows: Reference: J-STD-002D - Surface Mount Process Simulation test




Q8: What is the solderability test pass/fail criteria for PPF lead frame? After the solderability testing, the termination on the units must show a minimum of 95% solder coverage free from non-wetting, de-wetting and pin holes. The 95% coverage criteria applies to the critical area of the termination. The lead termination for QFP packages is a gull wing configuration. The critical area in gull wing leads is the bottom of the foot (Area A) and the edges of the foot (Area B) per Figure 8. Figure 8: Critial Area for solderability of Gull Wing Leads in QFP Packages Reference: J-STD-002D Appendix A

Figure 9 shows examples of passing PPF Surface Mount solderability testing units that used Sn63/Pb37 solder paste and lead free solder paste. Figure 9: Solderability (Surface Mount Process Simulation test):

Item PPF Lead Finish Soldering

type Eutectic

(Sn63/Pb37) Lead free

(Sn96.5/Ag3.0/Cu0.5) Criteria Solder thickness wetted fillet evident is acceptable. Solder thickness wetted fillet evident is acceptable. Result PASS PASS

Attached




Q9: What solderability testing data has Xilinx collected on PPF lead finish? Xilinx has performed surface mount solderability testing on PPF units at time zero after assembly and after uHAST 96 hours testing, HTS 1000 hour testing and Temperature Cycle Condition 1000 cycle testing with no failures seen. See Figure 10 for data. Figure 10: PPF Post Stress Surface Mount Solderability Results

Q10: What is the lead fatigue test pass/fail criteria? For the fatigue test, PPF can meet a criteria of mass weight:1.05 oz and >3 cycles without any lead broken or crack. This is defined in JESD-B105. (Refer to Table 7.) Table 7: Fatigue test:

Test item Data Cycle Lead fatigue test

(Mass weight:1.5oz) Avg S.S : 0/10, Pass




Q11: Are Sn whiskers any concern with PPF lead finish? For the Sn whisker, the PPF L/F does not have this phenomenon. Refer to JEDEC/IPC publication in Figure 11. Figure 11: Sn whisker:

Q12: How to fine tune the recipe for inspection machine? PPF leads will appear as a darker color and its lightness may be a little different under an inspection machine. The recipe of lightness on the inspection machine may need to be adjusted. Before recipe fine tune After recipe fine tune



10 www.xilinx.com XTP526 (v1.2) November 23, 2020

Q13: Will the affected products’ MDDS be updated? Yes, the affected products’ MDDS have been revised to show the Ni/Pd/Au lead finish and can be found on Xilinx.com. Instructions on how to find the MDDS for specific product/package combinations are in https://www.xilinx.com/support/answers/21277.html.

Revision History The following table shows the revision history for this document:

Date Version Description of Revisions

10/29/2018 1.0 Initial release.

03/30/2020 1.1 Revised Q1 CY20 to device date code DC2001.

11/23/2020 1.2 Updated answers 5 & 6, split question 7 into 10 & 11, and added questions 8, 9, 12 & 13.

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lead-frame plating composition change for legacy ......lead-frame plating composition change for...

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