Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Solder mask materials and equitements wanted

Xingsheng

#14512

Solder mask materials and equitements wanted | 27 August, 1998

Hi, Friends, Could you please recommend me some solder mask materials and equitements for high quality solder mask? Details such as company name, phone numer et al are welcomed. Thanks! Have a good day Xingsheng

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Dave F

#14513

Re: Solder mask materials and equitements wanted | 29 August, 1998

| Hi, Friends, | Could you please recommend me some solder mask materials and equitements for high quality solder mask? Details such as company name, phone numer et al are welcomed. Thanks! | Have a good day | Xingsheng Xingsheng: Consider the following points. Dave F 1. SMTNeters focus primarily SMT board assembly and secondarily on PTH board assembly. Your question applies to board fabrication. The question is interesting and there may be people that participate in this forum that can help you, but you may also want to consider posing this question to the folks at IPC TechNet Forum (http.www.ipc.org). 2. Additional information on the three solder mask technologies that we discussed earlier is: 2A. Wet film. Specify a standard wet film screen solder mask (i.e., Warno, Hysol SR1000), if a minimum of 0.010 inch clearance on each side of pads is available. Wet film will work well on PTH and sparsely populated SMT boards. Pros: Cautions: Low cost Limited resolution Fast process High operator sensitivity Excellent mechanical and chemical properties High set-up cost Vulnerable to voids, bubbles, skips, and pinholes 2B. Dry film. Specify a photo-imageable dry film mask (i.e., DuPont Vacel 8030) if a minimum 0.003 to 0.005 inch clearance on each side of the pad is available. However, the space between the pads can be no less than 0.008 inch for effective adhesion. For very small pads, the mask clearance must be greater for wave solder applications, because the mask act like a cliff and cuts the molten solder off before it contacts the pad. Typical tolerance is �10%. Pros: Cautions: Very little waste Adhesion to substrate not as good as LPI Good resolution Conformance to surface features not great Uniform coverage High cost of material and equipment Low set-up cost Storage in controlled environment required Fast process time Can tent holes 2C. Liquid Photo-Imageable (LPI). LPI is fast becoming the standard mask for SMT applications. It requires a clearance of 0.001 to 0.0015 inch on each side of the pad. This is very attractive for fine pitch applications, because it is a thin coating, but LPI: Pros: Cautions: Excellent resolution High cost of material and equipment Excellent adhesion Can not tent holes Excellent conformance to surface features Process more difficult to control Excellent mechanical and chemical properties High set-up cost Vulnerable to voids, bubbles, and pinholes A cost and delivery comparison of these types of masks follow: Factor Wet film Dry film LPI Cost Least Wet film X 1.15 Wet film X 1.05 Lead time: If the fabricator Has capabilities none none none Jobs work out none 1 - 3 days 1 - 3 days

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