Eddies information is correct. Also, use IPC SM-840 for thickness call out.
James Hofer
Director of Operations
Accurate Circuit Engineering
3019 S. Kilson Dr.
Santa Ana Ca. 92707-4202
714-546-2162 work
714-473-6127 cell
[log in to unmask]
----- Original Message -----
From: "Eddie Rocha" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 29, 2004 8:32 AM
Subject: Re: [TN] LPI soldermasks
> 1 mil (25 microns)minimum thick of LPI soldermask isn't achieved across
the
> entire bd with a standard LPI coating process. The thickness is less over
> conductors. The thicker the conductor the thinner the LPI will be. With
> standard outer layer conductor thicknesses (.5 oz copper plus .001" copper
> plating) a .7 mil (~17 microns) minimum LPI thickness is typically
achieved.
>
> As far as color, green is a standard color for fabricators. Changing the
> color requires the fabricator to empty his LPI coating machine reservoir,
> change screens, and in most cases change his tack drying oven
temperatures.
> These changes impact the fabricator's efficiency and reduces his thru-put.
>
> A matte or semi-matte LPI surface is believed to help reduce solderballs
> during the assembly process. A glossy surface is hard on the inspectors
due
> to the excessive reflection under inspection lights.
>
> That's my input, hope it helps.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Juan T. Marugán
> Sent: Wednesday, July 28, 2004 11:29 PM
> 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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