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Lead Free MLCC, Chip-R, MLCI 

 

 

 

SMA Application Guideline 

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Background 

Pb free solder material was started in 1995. A 
composition of (Sn-4Bi-2Ag-0.5Cu-0.1Ge) was 
announced in July 1998, though, since later it was found 
that for 42 alloy (most popular material fore lead frame), 
wetting and joint strength was insufficient and further 
“Life-off” problem was newly found, the composition was 
reviewed and resulted in the present composition. 
According to the test data shown in that meeting, major 
components  (QFP, Chip-R, MLCC) were tested and 
significant difference in mechanical strength was not 
found compared with Sn/Pb solder. Some of Japanese 
electronic equipment providers  may think technical 
problems were to some extent cleared. However, since 
the data was just experimental and looked at only one 
aspect, different reliability problems might come up from 
each device manufacturer. The company also 
mentioned the solution as “latest” and “maybe not final”. 

Concretely technical standards for some test items were 
given by Sony. The standards are to test wetting and 
robustness of electrical components quantitatively. For 
some tests, use of special test equipment is required, 
however some of them can be replaced by other 
methods that require none of special equipment. 
Particularly for wetting test, “self-alignment method” can 
be used, because self-alignment effect seen in reflow 
soldering process depends large part on wetting.

 

Sn/Pb Phase Diagram 

(Engineering version) 

An alloy cannot necessarily be soldered at its melting point. 
At or slightly above its melting temperature the alloy is still 
sluggish, does not flow very easily, and seems to have 
restraint in its wetting characteristics. 

A good rule of thumb to use a range of approximately by 
33~90

°

C above the melting point for soldering operation, this 

range is suitable for most alloys. 

For 63/37 solder alloy, recommended alloy temperature 
during wetting around 245~275 

°

C. 

 

Figure 1. Sn/Pb Phase Diagram (Ref. “Solders and Soldering 3rd 

edition”, Howard H. Manko)

 

 

The proposal of Infineon, Philips and STMicroelectronics contains an upper limit for “lead-free” components of 0.1% related to 
the individual material, not to the whole package or component. The “lead-free” products give at least their European clients a 
certainty to be “green” in time. Although legislation has not yet been consolidated, a max. level of 1000ppm is mentioned in 
the law of some countries. 

Note: Shipping materials such as blister tape and paper based boxes are not part of this consideration, since they are usually 
part of existing recycling processes. 

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Evaluation of Pb Free solder paste 

 

Score=1 means very good, score=6 means very poor. Score=10 means extremely bad 

 (Ref. and rated by Soldertec Ltd.) 

 

Sn-3.5Ag 

Sn-Ag-Cu 

*8

 

Sn-Ag-Cu-Sb 

*9

 

Sn-0.7Cu 

Sn-Bi-Ag 

Sn-Zn-Bi 

Melting/Process temperature 

5 

3.5 

3.5 

6 

2 

1 

Peeling off after soldering 

*1

 

2.5 

2.5 

2.5 

2.5 

5.5 

5.5 

Solderability 

*2

 

4 

2 

3 

5 

1 

10 

Profile 

*3

 

3 

1.5 

1.5 

5 

4 

10 

Reliability 

*4

 

3 

1.5 

1.5 

4 

5 

6 

Recycling 

*5

 

2.5 

2.5 

2.5 

2.5 

5 

6 

Cost 

*6

 

4.5 

4.5 

4.5 

1.5 

4.5 

1.5 

Alloy authorization 

*7

 

1.5 

3 

4 

1.5 

5 

6 

Total score 

26 

21 

23 

28 

32 

46 

Average score 

3.3 

2.6 

2.9 

3.5 

4.0 

5.6 

 

*1

  Bi alloy easy to peel-off or lift-off after soldering, as well as not so environmental friendly. But Bi is helpful in wettability and 

solderability and to reduce soldering temperature. 

*2

  Zn alloy easy to be oxides, powerful flux is required. 

*3

  The advantage of Sn-Ag-C u   (-Sb) and Sn-Bi-Ag is able to apply lower solder joint temperature. However, need to 

considerate the soldered peel-off issue by applying Sn-Bi-Ag. 

*4 

It is average performance; the ranking might be changed under different application conditions. 

*5 

Zn and Bi will also created issues/costs, same situation as other alloys. 

*6 

The approximately of related costs is depended on Ag content. Tin strip is efficient than Solder paste. 

*7 

Sn-Ag-Cu is secured by some patents; some authorizations and patents secure Sn-Ag-Cu-Sb; Sn-Bi-Ag and Sn-Zn-Bi are 
secured in various ways  of patents. 

*8 

The recommended composition : Sn- (3.4~4.1)Ag- (0.5~0.9)Cu 

*9 

Standard composition : Sn-2.5Ag-0.8Cu-0.55Sb

 

 

 
Pb Free Components from Walsin Technology 

New coating technology, then offers advantages beyond the simpler elimination of lead : 

l

 

Pure tin termination coating. 

l

 

Improved shelf life because of low intermetallic growth. 

l

 

Improved solderability because of neglible degradation of the solder surface. 

l

 

No whiskers and no lead. 

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Recommended IR Reflow Soldering Conditions 

Ÿ

 

The following Lead free solderpastes are suitable to be applied with WTC components : 

1. 

Sn-3Ag-0.5Cu series

 of Lead free solder paste. Recommended by JEITIA on Jun.-2000. Typical ally melting 

point at +225~230

°

C. 

2. 

Sn-(3.7~4.1)Ag-(0.4~0.8)Cu series 

(e.g. Multicore Sn-3.8Ag-0.7Cu) of

 

Lead free solder paste. Recommended 

by NEMI. 

3. 

Sn-2.5Ag-0.5Cu-1Bi series 

(e.g. Senju #OZ-7085-340F-32-12) of Lead free solderpaste. Typical alloy melting 

point at +222

°

C. 

4. 

Sn-2.2Ag-20In series

 (e.g. Indium Indalloy #227) Lead free solderpaste. 

 

Ÿ

 

Soldering profile  : 

 

Fig 2. Infrared soldering profile for Lead-Free SMD 

 

Others 

For more information, please contact with 

Application Group, R&D Dept., Walsin Technology : 

 

e-Mail 

: 

PCDA1@PASSIVECOMPONENT.COM

 

Fax 

: +886-7-8136745 

Address  : 1, West 13 Street, Kaohsiung Export Processing Zone, Kaohsiung, Taiwan, R.o.C.