In fact this was the 1 issues that I can see. I will recommend using the IPC-SM-840 to cover the thickness requirement. This is based on the materials ability to withstand 500 VDC without leakage. As far as the mask finish - LPI material come in so many flavors that I think it is important to develop a matrix of acceptable LPI types in your PCB specification. This will allow for good control of specific LPI part numbers from suppliers that meet you needs for flux types, conformal coating compatibility, etc. Letter screen inks should also be a part of this requirement. The most effective method would be to solicit this information from your suppliers as these will be the ones that are currently working for you. Any new suppliers/materials could undergo a controlled testing program to ensure compatibility with your process.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Paulus, Jim [mailto:[log in to unmask]]
Sent: Thursday, July 29, 2004 9:44 AM
To: [log in to unmask]
Subject: Re: [TN] LPI soldermasks
We would also appreciate comments to Juan's questions, as we are engaged in the same activity of updating drawings. Regards LPI mask thickness, is it realistic to require a 1 mil thickness? Jim Paulus at Itron: 507-837-4326 at office: 608-787-0817
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Juan T. Marugán
Sent: Thursday, July 29, 2004 1:29 AM
To: [log in to unmask]
Subject: [TN] LPI soldermasks
We are reviewing our documentation in order to avoid lacks or misunderstandings in the requirements written in our drawings.
At present we define:
a)The type of soldermask: LPI iaw IPC-SM-840, Class H,
b)Thickness: 25µm minimum
c)Conductor finish: ENIG
Apart from these requirements, we would like to know if other kind of properties, like color (green, black...) and surface finish (gloss, semi- gloss or mate) should be defined in the drawings.
Can somebody give me some information about the influence of both parameters -color and surface finish- in the quality of the assembled board? That is, when or in which type of applications is important to specify these parameters?
We have also another question. Sometime we have had adhesion problems. To check it, we performed a tape test. Is there another test to verify the quality of the soldermask during incoming inspection?
Thank you for your comments and best regards from Spain,
Juan T. Marugán López
Production Quality
Defense Electronic Equipment
www.indra.es
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To unsubscribe, send a message to [log in to unmask] with following text in
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To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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