1X
High 高
Very Limited 很少
Limited 较少 1X
Limited 较少
Hazard to Manufacture
High
Moderate
Low
对生产者的危害
高
中等
低
High
Low

高
低
PCB Surface Finish Selection/PCB表面镀层的选择(2)
Different Finish Characteristics/不同镀层的特点 ➢OSP: can withstand higher processing temperatures. However, multiple heating cycles can induce degradation in wettability. 能耐较高的工艺温度,但是,多次加热将使可焊性变差 ➢NiAu: NiAu is a popular surface finish, It has the widest process window as compared with the other surface finishes, and is very good for multiple heating cycles. The occasional occurrence of “black pad” with the Electroless Nickel – Immersion Gold (ENIG) finish poses certain reliability concerns, Electrolytic Ni/Au may be used to prevent the occurrence of “black pad”, For area array packages, NiAu finishes may not be the best from the reliability point of view. NiAu是一个广泛使用的镀层,和其它的镀层比较,它有较宽的工艺范围,适合多次加热.对于ENIG(化学镀 镍浸金工艺)常常会会出现”黑焊盘”现象,从而出现可靠性问题.使用电解NiAu能避免”黑焊盘”的出现.从 可靠性的角度来说, NiAu对于面积列阵封装并不是最好的镀层.
.
PCB Surface Finish Selection/PCB表面镀层的选择(3)
➢I-Sn: Immersion Tin is one of the surface finishes that has been considered to replace HASL. This surface finish has the second best wettability as compared with NiAu if used for only 1 heat exposure, as the solderability of I-Sn degrades rapidly with the number of heat cycles. I-Sn finish is good for press-fit connectors. 浸锡是被当做能替代HASL的镀层,如果仅仅只加热一次,它有仅次于NiAu的可焊性,但随着加热次数的 增多,它的可焊性很快地下降. ➢I- Ag: Immersion Silver is another surface finish that can replace HASL. The wettability of I-Ag is better than OSP, The chemistry, thickness, and process control are critical to the performance of I-Ag. 浸银是另一个能替代HASL的镀层,它的可焊性比OSP好.化学,厚度和工艺的控制对于它的性能有很重 要的影响.
PCB Surface Finish Selection/PCB表面镀层的选择(6)
Wetting Force(润湿力): (fresh & baked) Ag > ENIG > HASL > Sn >> OSP
PCB Surface Finish Selection/PCB表面镀层的选择(7)
Good 好
Wire Bonding 线焊接
Cost (To HASL) 成本(相对HASL)
Availability 实用性
Not Recommended 不推荐
1X
Limited 较少
2X
High 高
Moderate 中等
Not Recommended 不推荐
0.3X
Not Recommended 不推荐
Au:3-8 Ni50-150
Excellent 优秀
8-20
Excellent 优秀
ImSn 40-60
Excellent 优秀
ImAg 3-12
Excellent 优秀
Contact Connections (接触式连接器)
Fair 一般
Good 好
Not Recommended 不推荐
Good 好
PCB Surface Finish Selection/PCB表面镀层的选择(4) Wettability(可焊性):
Ag > ENIG, HASL > Sn > OSP
PCB Surface Finish Selection/PCB表面镀层的选择(5)
Spreading(展开性): HASL, ENIG > Sn > Ag > OSP
PCB Surface Finish Selection/PCB表面镀层的选择(1)
Thickness (microinches) 厚度(微英寸)
Fine Pitch Quality 小间距元件质量
PCB Surface Finish Summary
HASL
ENIG
OSP
100-10000
Poor 差
Pull strength of LF QFP solder joints/LF QFP焊角拉力:
OSP > HASL > Ag > Sn > ENIG
Failure of ENIG has been observed to occur at interfaces of Ni-Cu and Ni3Sn4 在Ni-Cu和Ni3Sn4界面已发现ENIG失效.