Thanks I'll check it out. When the paste is bad it is pretty obvious when it won't separate from the squeegee blade and smears rather than get a clean sweep with the squeegee blade set at 13 lbs instead of the normal 8lbs. Most of the other paste we use works really well so we dropped one vendor after three bad date codes. We had the vendor over and had the tubes from each batch tested and they confirmed the viscosity was bad. We didn't need to buy a viscosity meter. We followed the manufacturers specifications in their tech sheet to the letter. How would the 650 test methods help us in day to day operations? Small companies don't have qual labs and don't have time to do anything but follow good paste controls, proper application, storage and shelf life etc.
How do you think it would help? 

-------------- Original message -------------- 
From: Graham Naisbitt <[log in to unmask]> 

> Hi Techies 
> 
> You might benefit from using the IPC-TM-650 2.4.35 and 2.4.43 thru 46 
> test methods to control your paste prior to use on the line. 
> 
> Although these are currently in review for lead-free, I have some info 
> to share if it will help. 
> 
> Graham Naisbitt 
> Co-Chair TM-650 Test Methods Sub-Committee 
> 
> On 2 Nov 2008, at 19:53, john queen wrote: 
> 
> > 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 th e 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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