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November 2008

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Subject:
From:
John Goulet <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Sun, 2 Nov 2008 21:54:14 +0000
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I just found Greg's E-mail for the Consortium's Report.
Phase 1 was SMT, Phase 2 was thru-hole, Phase 3 was PTH repair SAC305 versus SN100.
Morose, [log in to unmask]


-------------- Forwarded Message: -------------- 
From: [log in to unmask] 
To: TechNet E-Mail Forum <[log in to unmask]>, john queen <[log in to unmask]> 
Subject: Re: [TN] Controlled RH% Versus Screenprinting Results 
Date: Sun, 02 Nov 2008 21:47:20 +0000 

The exact DOE would be confidential to the comapny I workd for at the time. All I can say is that we ordered enough boards of each finish and each company in the consortium donated parts, stencils, build, inspection and test time or services. The results were that some pastes were excellent for certain finshes. An OEM has control over the board finish but a contract assembly house doesn't. We build whatever we get from te customer, therefore we had to choose a solder past that works the best for all,  knowing full well it wasn't the best paste for one of the finishes.

If you would like a report you may request one from Gregory Morose - University Lowell Mass, TURI  (Toxic Use Reduction Institute). The EPA gave us a grant to reduce the development for the PB-free process development.
Our consortium was different in that it covered the requirements of building large boards more typical in our industry. 
A lot of the data from China's build of cell phones wasn't typical of our products and we can't put ours in protective foam to make them look as reliable as tin/lead and we can't change the reliably from 5 years to 2 to meet quality goals.


-------------- Original message -------------- 
From: john queen <[log in to unmask]> 

> This is an interesting one can anyone share there DOE of paste selection and 
> printer setup 
> ----- Original Message ----- 
> From: "John Goulet" 
> To: 
> Sent: Sunday, November 02, 2008 7:01 PM 
> Subject: Re: [TN] Controlled RH% Versus Screenprinting Results 
> 
> 
> The viscosity of the solder paste also varies greatly with temperature 
> change 
> that is easier to control. I've had to resolve the same issue at other 
> companies and currently resolving it in this building and layout again. 
> Here are some things to consider before spending $500K. 
> 1. Is the Receiving Dock and Incoming area totally sealed off from the SMT 
> area. It is pretty hard to manage temperature and humidity control with 10' 
> doors open many times a day. In one factory we put up a frame and sheet 
> rock walls around the dock and another for the receiving area. Problem gone. 
> 2. Are the air handlers equipped with programmable thermostates. If they 
> aren't and they don't have the dehumidifier options in them then at night 
> they 
> will blow in cool damp air because it is cool enough the air-conditioner 
> will be 
> acting as a fan only. In the current factory we going to do this before 
> summer. 
> Hopefully we'll also separate our SMT area as stated in #1. 
> 3. Try some of the newly released solder pastes. Indium just came out with 
> 6.3 WS tin/lead that is far better than the 6.2. Senju may not be well known 
> in the USA but in an extensive DOE they were the best for all finishes. 
> Senju is 
> the #1 paste overseas. 
> 4. The paste storage and handling in the productin line to prevent the flux 
> from separating is important. A low voume high mix shop may need to buy 
> 5000 gram or less and not the 7000 gram tubes since you can't put them back 
> in the refrigerator. Large beads of paste over 1/2" may be easier for the 
> operator but in higher humidity and temperature the paste on the stencil is 
> going to change for the worse. The paste spec is written for beads up to 
> 3/4" 
> but that is in ideal RH and temp situations. Small factories that weren't 
> designed for this industry are prone to the same situation that you have. 
> One 
> large factory had a huge sock like air exhange units that blew in whatever 
> air 
> is outside. In the winter you can have small humidifiers added but in the 
> rainy 
> spring and humid summer you have to relay on using the best paste and very 
> good handling controls. Keep the jar low on the rack or floor since since 
> with 
> air conditining the floor will be at a lower temperature approximately 72F. 
> The 
> temperature in the machine it may reach 78-80 if you didn't add the small 
> fan 
> for the summer months. In this way when the operator adds the paste you'll 
> stay in the middle of the control range. 
> 
> 
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