PD 944 and PD 945
SMT Adhesives

                                                                                             Thermosetting Polymer SMT Adhesives
Description
PD 944 and PD 945 are thermosetting single-component, solvent-free polymer adhesives, developed especially for the surface mounting of SMT components on to PCBs and for use on bare substrates.
The difference between the adhesives is in the viscosity. The PD 945 has the higher viscosity.
Special advantages
- Very wide processing window, no tendency to string.
- Suitable for standard and for high-speed dispensing.
- Form stable glue dots.
- Excellent adhesion with standard and also with difficult-to-glue components.
- Very low humidity absorption. Steep temperature increases and very short curing times are possible without danger of formation of air bubbles or worse adhesion.
- High green strength, especially PD 945.
- High surface insulation resistance (SIR).
- Constant batch-to-batch quality.
Physical characteristics
Colour: red
Density: 1.2 g/cc
Glass transition temp.: approx. 80 °C
Homogeneity: no particle > 50 μm
Adhesion: ³ 25 N/mm2 at room temperature,
after curing in conventional box oven, 4 min /125°C, Cu-nail on SO component, with a low-stress incapsulation compound.
Viscosity
Shear rate D Viscosity ascending curves
[s-1] [Pa·s]
PD 944 30 15-50
PD 945 30 30-65
Haake Rotovisco RV 20, PK 100, PK I/2°T,
plate/cone, without border, temperature: 23 °C.
Program: ascending curve 0-40 s-1, 6 min.
Electrical characteristics
Surface insulation resistance and electrolytic corrosion properties:
see reverse.
Processing
The adhesives are suitable for:
- Machine and manual
dispensing: PD 944 and PD 945.
- Screen printing: PD 944.
- Stencil printing: PD 944 and PD 945.
- Pin-transfer technique: PD 944.
Curing in a continuous furnace
The standard curing conditions are: 125°C / 3’. Max. curing temperature should not be higher than 200°C. The min. curing times are shown in the following list.
100 °C         125°C         150°C            180°C
     8 '                 3 '                 1.5 '                  1 '
Cleaning
Before curing:
The uncured adhesive can be removed with Zestron HC and other Zestron and Vigon cleaning materials - see separate application recommendations.
The cleaned parts must be completely dry before installing them in the machine.

After curing:
Because of the known residual thermoplasticity of the cured adhesive, defective components can be easily replaced by heating (with hot air) the cured adhesive joint above 100°C. After removing the component (torsion movement), the hot air should be focused on the remaining adhesive in order to remove it with a sharp tool.
Packing
The adhesives PD 944 and PD 945 are available in various machine-specified syringes.
Storage
Storage time:
6 months in a refrigerator, at a storage temperature of 5 - 12°C. Storage in a refrigerator is recommended. Remark: Storage at temperatures >30°C should be avoided. See reverse for additional information.

Test results with the SMT-adhesive PD 944 according to Siemens norm SN 59651**
Date: 21 April 1994
Note:*      Remarks                                                  Requirements                                                             Results
3.1          Characteristics                                         good visible colour, bubble-free,                                coloured red
                                                                                filled in syringes                                                         bubble-free
3.2          Electrolytic corrosion effect                      known value should be no worse                                passed
               according to DIN 53489                            than AN 1.4
3.3.1       Surface insulation resistance                    > 1.108 Ohm                                                              4d:3.0.1010 Ohm
               (comb sample test)                                                                                                                      21d:9.0.1010 Ohm
3.3.2       Electrolytic corrosion effect/                      no dendritic growth                                                     passed
               comb sample test
3.6          Components’ adhesion
               before curing of adhesive
                                                                                position change £ 0.1 mm                                            passed
               Components’ adhesion                                                                                                               0207: 2.21 N
               after curing of adhesive/                                                                                                                1206: 1.92 N
3.7          measured in the                                        > 0.2 N per component                                                 0805: 1.21 N
               soldering bath                                                                                                                                0204: 0.75 N
                                                                                                                                                                     SOT 23: 2.70 N
4.2          Open potlife                                              min. 8 hours                                                                 passed
4.3          Dispensability                                           reproducible - without stringing                                    passed
4.4          Tack time                                                  min. 3 hours                                                                 passed
4.5          Adhesive spreading during curing            diameter increase £10%                                              6 %
4.6         Curing characteristics                                acc. to manufacturer´s data                                         IR: 125 °C, 3 min.
4.7         Cleanability                                                completely with solvent                                                cleanable
4.8         Reparability                                               SMD replacement                                                         passed
                                                                                without damage
* According to SN 59651.
** The tests were performed in the Siemens Central Laboratory in Berlin.