Hi Borch,
Ok clearer. I understand you are talking about electroplated gold. As I understand this issue, it is gold volume that is the problem. If the percentage of gold in the resulting joint is above 3-4 percent, the joint can become brittle. There are two places in IPC standards where this is mentioned. These are shown below. As I know some people recommend that you make a solder volume calculation to estimate your final gold concentration range.
From IPC-6012
3.2.7.5 Electrodeposited Gold Electrodeposited gold plating shall be in accordance with ASTM-B-488. Purity and hardness
shall be specified in the procurement documentation. The thickness shall be as specified in Table 3-2 (Code G, GS,
GWB-1 and GWB-2).
Note: Industry investigations have shown that a gold-tin intermetallic phase forms under normal soldering process parameters when the weight percent of gold in the solder joint reaches the 3-4% range. Refer to IPC-J-STD-001 and IPC-HDBK-001 for further information on gold removal to prevent the formation of brittle solder joints resulting from high concentrations of gold dissolving into the solder joint.
And from IPC/J-STD-001
4.5 Removal of Component Surface Finishes Certain surface finishes on component terminations or PCB lands may
impact the quality of the solder connection. Follow the requirements of 4.5.1 and 4.5.2.
The following requirements may be eliminated:
a. If there is documented objective evidence, available for review, that there are no gold related solder embrittlement issues,or other metallic surface finish solder joint integrity problems (e.g., with Sn or SnBi) associated with the soldering process being used (see IPC-HDBK-001 or IPC-AJ-820 handbook for guidance).
b. For electroless nickel immersion gold (ENIG), nickel-palladium-gold (NiPdAu), or electroless nickel electroless palladium immersion gold (ENEPIG) finishes.
4.5.1 Gold Removal Gold shall [N1P2D3] be removed:
a. From at least 95% of the surfaces to be soldered of the through-hole component leads with 2.54 μm [100 μin] or more
of gold thickness.
b. From 95% of all surfaces to be soldered of surface mount components regardless of gold thickness.
c. From the surfaces to be soldered of solder terminals plated with 2.54 μm [100 μin] or more of gold thickness.
A double tinning process or dynamic solder wave may be used for gold removal prior to mounting the component on the
assembly.
Best regards,
Dave
David W. Bergman 大山人
Vice President, International Relations
IPC - Association Connecting Electronics Industries
3000 Lakeside Drive Suite 309S Bannockburn, IL 60015-1249 USA
+1 847-597-2840 tel
+1 847-615-5640 fax
+1 847-867-1388 mobile
[log in to unmask]
Skype: davidbergmanipc
www.ipc.org
-----Original Message-----
From: Borch Li [mailto:[log in to unmask]]
Sent: Thursday, November 18, 2010 12:43 AM
To: Listserv TGAsia; David Bergman
Subject: RE: [TGAsia] PCB金镍层厚度测量位置哪个IPC有说明
谢谢,我说的是整板电金板.有客户居然发现SMT焊接不良后,通过测试孔环位置的金厚(金厚正好比客户要求高一点点),把问题推给PCB金厚过厚引起焊接不良.
Best regards&Thanks!
BU-PLG(QA): Borch Li
李保春
Tel:25234/695362
-----Original Message-----
From: TGAsia [mailto:[log in to unmask]] On Behalf Of David Bergman
Sent: 2010年11月17日 23:56
To: [log in to unmask]
Subject: Re: [TGAsia] PCB金镍层厚度测量位置哪个IPC有说明
Hi Borch,
I assume you are asking about ENIG.
IPC-4552 Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards recommends the use of XRF for this thickness measurement. I did not find a specific recommendation as to the preferred measurement location on the ENIG coated surface.
Best regards,
Dave
David W. Bergman 大山人
Vice President, International Relations
IPC - Association Connecting Electronics Industries
3000 Lakeside Drive Suite 309S Bannockburn, IL 60015-1249 USA
+1 847-597-2840 tel
+1 847-615-5640 fax
+1 847-867-1388 mobile
[log in to unmask]
Skype: davidbergmanipc
www.ipc.org
From: TGAsia [mailto:[log in to unmask]] On Behalf Of Borch Li
Sent: Tuesday, November 16, 2010 7:58 PM
To: Listserv TGAsia
Subject: [TGAsia] PCB金镍层厚度测量位置哪个IPC有说明
Hi All,
哪位兄弟知道PCB金镍层厚度测量位置哪个IPC有说明.谢谢
Best regards&Thanks!
Multek B5 PQE
Borch Li
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